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275 Cards in this Set
- Front
- Back
The field of biology that studies the transfer of traits from one generation to another
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genetics
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This position of the codon is the most degenerate
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third
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The genetic code is represented by
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64 possible triplets of four bases (A,G,U,C), codons
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polycistronic
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mRNA which has more than one cistron or gene. Encodes for several proteins
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Describe the flow of genetic information
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Transcription - Genetic information contained in DNA is copied into mRNA
Translation - mRNA relays information to synthesize protein molecules |
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This many codons code amino acids
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61
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Alanine is encoded by:
GCU GCC GCA GCG The first two bases in each triplet are identical. Because of the degenerate nature of the third position, this is true: |
the third base in each codon can be any of the four bases and the same amino acid will still result.
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Many amino acids are represented by more than one codon. This means the code is:
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degenerate
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The total complement of genes found in a cell
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genome
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polycistronic mRNA is found in:
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prokaryotes
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The flow of information in the cell, from DNA to RNA and eventually to proteins
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The Central Dogma
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Typical E. coli contains ______ different genes
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3000-4000
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Genetic composition of an organism
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genotype
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codons
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Four bases (A,G,U,C) arranged into 3 letter words, or triplets
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There are this many possible codons
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64
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when an organism expresses observable characteristics
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phenotype
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61 codons do this:
3 codons do this: |
code for amino acids
signal the termination of protein synthesis |
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There are four different bases arranged in triplets which make 64 possible codons. These represent:
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the genetic code
|
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the information containing region of the chromosome which is translated into an RNA message
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gene
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It states that such information cannot be transferred back from protein to either protein or nucleic acid.
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The Central Dogma
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Prokaryotic mRNA often has more than one coding region which allows it to encode several different proteins per mRNA molecule. This makes prokaryotic mRNA:
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polycistronic
|
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These signal the termination of protein synthesis
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UAA
UAG UGA |
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UAA, UAG, UGA are called
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nonsense or termination codons
|
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nonsense codons:
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signal the termination of protein synthesis
|
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Four bases (A,G,U,C) arranged into 3 letter words, or triplets:
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codons
|
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when an organism expresses observable characteristics
|
phenotype
|
|
61 codons do this:
3 codons do this: |
code for amino acids
signal the termination of protein synthesis |
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There are four different bases arranged in triplets which make 64 possible codons. These represent:
|
the genetic code
|
|
the information containing region of the chromosome which is translated into an RNA message
|
gene
|
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It states that such information cannot be transferred back from protein to either protein or nucleic acid.
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The Central Dogma
|
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Prokaryotic mRNA often has more than one coding region which allows it to encode several different proteins per mRNA molecule. This makes prokaryotic mRNA:
|
polycistronic
|
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These signal the termination of protein synthesis
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UAA
UAG UGA |
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UAA, UAG, UGA are called
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nonsense or termination codons
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nonsense codons:
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signal the termination of protein synthesis
|
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Four bases (A,G,U,C) arranged into 3 letter words, or triplets:
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codons
|
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which microorganism was used in the DNA experiments
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S. pneumoniae
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who preformed the initial dna experiment proving dna to be the genetic material
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Griffith
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(s) strains of S. pneumoniae are ______while (r) strains are ____ what happened when they are both injected together
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smooth (S)- strains of S. pneumoniae are encapsulated and viruelnt while rough (R) strains
are not virueleunt (S)kills (R)does not when injected together- dead S strain with R, R is converted to S and kills organism |
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who preformed the experiment determing transformation of (R) to (S)
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Avery, MacLeod and McCarty
material that transformed R to S was insensitive to proteases and RNases but sensitive to DNases |
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Natural transformation
(or what led to transformed recipients) |
DNA isolated from cells of one strain could be taken up by another
|
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who determined the structure of dna
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Watson and Crick
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DNA Structure
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2 polynucleotide chains arranged in a double helix. The helix has a diameter of 20 Angstroms, and makes a complete turn every 34 Angstroms. There are 10 bp per turn of the helix. Hydrogen bonding link the bases between the strands. The nucleotides are joined to each other in a chain by covalent phosphodiester bond between the # 3 (3’) carbon of one to a # 5 (5’) carbon of the adjoining deoxyribose.
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what is the ratio of nuecleotide base pairs that vary in species of bacteria
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vary in proportion of G+C and A+T expressed as the mole % of G+C
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what us the range in bacteria and what does a high percentage mean
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range-22% to 74%
with a high percentage of G+C bonding tends to be more stable to unwinding or denaturation into single strands |
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what happens to DNA in spectrophotometers as it denatres
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As DNA denatures there is a sharp increase in their UV abs, @ 260 nm. The temperature that corresponds to the midpoint of their increase in absorption is their Tm
|
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what kind of bonds between A+T and G+C
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double bons in A+T triple Bonds in G+C
|
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Therefore the 2 polynucleotide chains in DNA helix are
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complementary (ie GCATAGC other is CGTATCG)
and anti parrallel |
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the antiparrallel arrangment of DNA chains results in polarity of the nucleotide chains which are
|
5' to 3' and the other chain is 3'to 5' so the 5'-PO(4) to 3'-OH
resulting in an overall negative charge |
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How many base pairs are in e.coli
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4.7X10^6
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what is the molecular whieght of the base pairs in e. coli
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2.5X10^9 daltons
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the chromosome molecule is how many times longer the e.colis length
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550 thus the molecule is twisted and supercoiled
|
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What individuals discovered the semiconservative model of DNA replication?
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Messelson and Stahl
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What isotope was used in the semiconservative model of DNA replication?
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E.coli was grown with 15N as the sole nitrogen source
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Describe how the semiconservative model of DNA replication was created?
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Grew E.coli, in 15N, as sole nitrogen source. This radioisotope was incorporated into the newly synthesized DNA molecule, after several generations the bacteria were transferred into a medium with normal nitrogen. DNA purified in an ultracentrifuge, and they observed, Generation 1, 2 and 3. In this system the DNA strands separate and each strand serves as a template for the daughter strands, as evidenced by the hybrid, 14N-15N labeled DNA.
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DNA replication is ____ and ____
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sequential and bidirectional
|
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enzymes that catalyze DNA synthesis add nulcleotides where
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to the 3'-OH end of the DNA
|
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Okazaki Fragments
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demonstrated that one of the DNA daughter strands was synthesized discontinuosly in short segments of 1000 to 2000 in a 5' to 3' direction these fragments are formed in only the lagging strand in replication
|
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how many different polymerases does e.coli have
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3
polymerase I,II,III |
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all polymerases catalyze what reaction
|
addition of mononucleotides to the 3'-OH end of a growing polynucleotide
|
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DNA polymerase III can polymererize how many base pairs per minute
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30,000
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DNA polymerase I is also called
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the Kornberg enzyme
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DNA polymerase I is involved in
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DNA repair of UV damage this repair is excision-repair mechanism of DNA
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what do all DNA polymerases require to add mononucleotides on the 3'-OH end
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a preexisting polynucleotide chain
|
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Where does DNA replication begin and end?
|
origin of replication on the circular DNA molecule of prokaryotes and proceeds in both directions to a terminus
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How was the process of DNA replication determined?
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By autoradiographs by Carins, 3H-thymidine, exposed lysed cells to photographic film, revealed the shpa and replication pattern of the replicating DNA
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What is theta replication?
|
When DNA was seen as a circular molecule with two replication forks.
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What is the function of initiator proteins in DNA replication?
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to recognize and bind to a specific DNA sequence of about 300 bases at the origin of replication
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What happens after the initiator proteins bind at the origin of replication?
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A protein complex binds to a DNA helicase, that unwinds short sections of the helix in advance of the replication fork
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What assists in the DNA unwinding and rejoining of the DNA molecule?
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DNA topoisomerases
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The rolling circle mechanism is another mechanism for DNA replication used in what?
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DNA replication in bacterial viruses; bacteriophages, and during DNA replication in conjugation
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What happens in the rolling circle mechanism?
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One of the strands is nicked at a specific site and the free 3’-OH end generated is extended by a DNA polymerase.
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What are the three forms of RNA?
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mRNA
rRNA tRNA |
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How are all three forms of RNA transcribed?
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from a DNA template by DNA-dependent RNA polymerase
|
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What is the sugar found in RNA?
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ribose and uracil replaces thymine
|
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RNA polymerase is a multisubunit consisting of what enzymes?
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Alpha
Beta Beta prime Sigma |
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The four subunits of RNA polymerase comprise the complete enzyme known as what?
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haloenzyme
|
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What is the initiation factor of RNA polymerase
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the sigma subunit
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What is the sigma subunit required for?
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promoter binding
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what is the largest enzyme known
and is a point of difference between the phylogenic groups |
RNA polymerase
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name the different phylogenic groups
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Bacteria, Archaea, Eukarya.
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Bacteria have how many different types of RNA polymerase with ___ different subunits
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1 type with 6 different sub units
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Archaea have how many different types of RNA polymerase with ___ different subunits
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several types each with 8-12 different subunits.
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Eukarya have how many different types of RNA polymerase with ___ different subunits
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several types each with 12-14 different subunits.
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What subunit dissociated from the core enzyme once polymerization begins?
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Sigma subunit
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What type of RNA is the most varied and comprises 5% of the total RNA?
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mRNA
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What is the life span of mRNA in a bacterial cell?
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a few minutes
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How does mRNA carry the genetic message?
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from the DNA template to the ribosomes
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In bacteria, mRNA commonly contains information for the amino acid sequence for several different polypeptide chains. This type of mRNA is known as what?
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polycistronic mRNA
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In E.coli how many enzymes are needed to synthesize histidine and are encoded in 1 mRNA molecule
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ten
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True of False. Not all base sequences in an mRNA molecule are translated into the amino acid sequence for polypeptides.
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True
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True of False. Translation starts at exactly one end of the mRNA molecule and proceeds to the other end.
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False. It rarely starts at one end. It may begin 100s of nucleotides in from the 5'-p terminus.
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When translation of mRNA does not start at one end (5'-p) , there is untranslated region known as what?
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the leader, which is usually 5-20 bases
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The polycistronic mRNA contains what type of sequences?
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spacer sequences that are 10 bases long and separate the coding sequences.
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What type of RNA is the smallest
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tRNA
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What is the structure of tRNA?
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cloverleaf structure folded back on themselves
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How is the unique structure of tRNA maintained?
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by internal base pairing which reults in the looks
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What are the modified bases of tRNA? Name two examples.
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methylated forms
Examples: pseudouridine and dihydrouridine |
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What molecule of RNA is involved with the translation of the genetic message?
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tRNA
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how many types of rRNA molecules are found in prokaryotic ribosomes and what are they
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3 types= 5S rRNA, 23S rRNA both found in the 50S ribosomal subunit. A 16S rRNA found in the 30S ribosomal subunit.
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what is the composition of rRNA in ribosomes and what is it for protien
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66% rRNA and 33% protien
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the intact rRNA particle is called what in bacteria
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70S ribosome
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what is the role of rRNA molecules in ribosomes
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they contribute to ribosome strucuture and have a functional role in protien synthesis
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in bacteria the _____ pairs with the initiation sequence site on the mRNA this does what
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16S rRNA, positions the mRNA on the ribosome
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the 23S rRNA is believed to be what type of enzyme and what is
it its role |
the peptidyl transferase associated with peptide bond formation during protein synthesis
|
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how much of the chromosomal dna encodes for the synthesis of rRNA and tRNA
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less than 1%
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both rRNA and tRNA are formed from _________ initially then cleaved into________
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larger precursors/smaller final products
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T/F both rRNA and tRNA are LESS stable than mRNA
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FALSE they are more stable than mRNA
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How does the bacterial cell make rRNA and tRNA ?
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The molecules are excised from large primary transcripts.
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____ is an adaptor of amino acids to mRNa codons at the ribosome, and incorporation into growing proteins.
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tRNA
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True of false. Each tRNA does not carry a specific amino acid.
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False. Each tRNA does carry a specific amino acid.
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What is the enzyme for the activation of amino acid-tRNA
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synthetase
|
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What is necessary to link the amino acid to the appropriate tRNA?
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ATP
|
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True of False. There is at least 1 tRNA for the 21 amino acids.
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True
|
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What loop is involved in the recognition at the ribosome in tRNA?
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Anticodon loop
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What are the other two loops of tRNA and what is their function?
|
pseudouridine and dihydrouridine and they are involved in the binding of the ribosome and the aminoacyl-tRNA synthetase
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True or False. The anticodon loop contains 3 bases that are in a sequence unique for each tRNA.
|
True
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RNA synthesis is in what direction?
|
5' to 3' direction of chain growth from the DNA template.
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True or False. Only one of the DNA strands is transcribed in any given DNA region (coding or sense strand).
|
True
|
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How does RNA synthesis begin?
|
With binding of RNA polymerase to a promoter DNA
|
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What are promoters in RNA synthesis?
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specific DNA sequences, usually 20-200 bases long
|
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DNA sequences that serve as promoters for the RNA polymerases are?
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-Pribnow box, sequence (TATAAT), (-10 sequence)
- -35 sequence, sequnce (TTGACA) |
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What sequence is found as part of all prokaryotic promoters?
|
TATAAT
|
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The TTGACA sequence is located where?
|
about 35 base pairs upstream from the polymerization start site
|
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In E. coli, rRNA transcripts contain ___ copy of each of 5S,16S, and 23S rRNA as well as __ different tRNA molecules.
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one copy of and 4 different
|
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T/F non-specific RNases excise the rRNA and tRNA from the rRNA transcripts
|
False highly specific RNases exisce the rRNA and tRNA from the rRNA transcripts
|
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T/F RNases produce the modified bases in tRNA
|
false other enzymes produce the modified bases in tRNA
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during RNA synthesis what happens to the area behind the core polymerase
|
the area reanneals and the new RNA dissociates fro the DNA template
|
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what is a termination sequence do
|
Termination sequences (several have been identified), cause the RNA polymerase to pause and terminate RNA synthesis
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what are rho?
|
Rho is a protein factor that binds to RNA and moves along the RNA until it reaches the RNA polymerase at the terminator where it unwinds the RNA-DNA hybrid
|
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name the two types of rho and there function
|
Rho independent is when the RNA polymerase synthesizes a polyU sequence, which results in a hairpin formation in the new chain. In rho dependent termination, rho binds to the RNA and moves along until it catches up with the RNA polymerase at a terminator, where it unwinds the RNA-DNA hybrid.
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What do TATAAT and TTGACA sequences do?
|
They instruct RNA polymerase where to start synthesis.
|
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True of False. The strength of the binding of the RNA polymerase to different promoters varies greatly.
|
True
|
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What are three ways promoters were discovered?
|
1. Mixed RNA polymerase with DNA
2. Treated this mixture with an enzyme that digested the DNA, this left the region bound to RNA polymerase intact. 3. Sequenced this DNA region and discovered the promoter regions. |
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Where does RNA synthesis begin?
|
with the binding of the RNA polymerase to the promoter, which causes the DNA strands to separate.
|
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What does the sigma subunit do in RNA synthesis?
|
It recognizes specific binding sites and ensures that the RNA polymerases forms stable associations with DNA only at promoters.
|
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True or False. In RNA synthesis only one turn of the DNA molecule is unwound at a time.
|
True
|
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When are ribonucleotides added during RNA synthesis?
|
after 8-10 base pairs are added to the growing chain
|
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What mediates elongation in RNA synthesis?
|
The core enzyme which is yielded from the sigma factor dissociating from the haloenzyme.
|
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True or False. Different sigma subunits have been determined for different bacteria.
|
True
|
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What are the five stages of RNA synthesis?
|
1. Promoter recognition, -10, -35.
2. Local unwinding, the RNA polymerase forms an "open promoter complex". 3. Chain initiation. 4. Chain elongation. 5. Chain termination. |
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in bacteria the initiating amino acid is what and what codon is this specified by and what it codes for
|
fmet or a formylathed methionine
the codons that specify this are AUG and GUG in the presence of the initiation complex it codes for the fMet-tRNA. |
|
in archaea the initiator tRNA is
________ |
unmodified methionine
|
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The initiation complex is formed from
|
the binding of the 30S ribosomal subunit to the initiation codon, AUG or GUG on the mRNA.
|
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what percent of all proteins in E.coli begin with methionine.
|
45%
|
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The initiation codon establishes what
|
the reading frame for the mRNA.
|
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T/F An initiator tRNA carrying fmet pairs with the initiation codon is in the presence of the 60S ribosomal subunit
|
false the tRNA carrying fmet pairs with the initiation codon is in the presence of 30s ribosomal
|
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what follows An initiator tRNA carrying fmet pairs with the initiation codon in the presence of the 30S ribosomal subunit
|
shine delgarno sequence
|
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what is the Shine Delgarno sequence
|
a purine rich region (3-9 bases) that precedes the 5’ end of the initiating AUG codon
|
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what is the role of the Shine Delgarno sequence
|
it specifies the ribosomal binding site on the mRNA.
|
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the initiation step of protien synthesis requires what type of ribosomal sub unit what type of RNA and what else
|
30S ribosomal subunit, mRNA, fmet-tRNA and 3 protein initiation factors, IF1, IF2 and IF3 and GTP.
|
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what is the purpose of the protien initiation factor IF3
|
catalyzes the dissociation of the 70S ribosome into individual subunits
|
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what other purpose does IF3 serve
|
IF3 is also associated with the binding of the 30S subunit to the appropriate site of the mRNA.
|
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what is the purpose of IF2 and GTP
|
they are both involved in the positioning of the fmet-tRNA to the correct codon on the 30S subunit.
|
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what does IF1 do
|
IF1 assists the IF3 in binding to the 30S subunit to the mRNA.
|
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give a brief summary of protien synthesis
|
The mRNA is read in the 5’ to 3’ direction.
A single mRNA can have several ribosomes attached to it (polyribosomes). This explains why little mRNA is required by cells for protein synthesis. Translation 10 to 20 seconds for a growing bacterium to synthesize protein of 300 to 400 amino acids. |
|
what does regulation refer to?
|
Control mechanisms for the synthesis of proteins.
|
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name the two categories of regulation
|
negative regulation and positive regulation.
|
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what happens during negative regulation
|
In negative regulation, an inhibitor is present in the cell and transcription is prevented
|
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what is the inhibitor present in negative regulation
|
The inhibitor is called a repressor
|
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what is the antagonist of the repressor
|
An antagonist of the repressor is generally called an inducer, it allows initiation of transcription.
|
|
What is protein synthesis?
|
A multistep process that takes place at the ribosome.
|
|
What are the three distinct steps of protein synthesis?
|
initiation
elongation termination |
|
How does elongation of protein synthesis begin?
|
with the binding of an aminoacyl-tRNA to the complementary codon on the mRNA at the ribosomal site.
|
|
The complementary codon of elongation determines what?
|
the type of amino acid inserted to the growing protein.
|
|
Recognition of elongation requires what?
|
2 protein elongation factors, EF-Ts (heat stable) and EF-Tu (Heat unstable) and the hydrolysis of GTP to GDP + Pi
|
|
The elongation factors of recognition of elongation promote what?
|
the binding of incoming aminoacyl-tRNA molecules to the ribosome.
|
|
describe positive regulation
|
In positive regulation, an effector molecule, activates a promoter, no inhibition is overridden.
|
|
what is the operon model
|
the first model for transcriptional control of protein synthesis discovered by Jacob and Monod
|
|
what is the operon model based on
|
lactose utilization in E. coli.
|
|
what does an operon consist of
|
1 or more structural genes that are under the control of a common operator.
|
|
what is the controlling factor
|
an activated repressor protein
|
|
what is induction
|
An example of a negative control system, in the absence of the controlling factor there is enzyme synthesis
|
|
what are the enzymes involved in lactose uptake and utillization
name thier substrate and what they are broken down into |
β galactosidase, which hydrolyzes lactose into glucose and galactose, (encoded on structural gene z).
β galactoside permease which transports the sugar into the cell, (encoded on structural gene y). Thiogalactoside transacetylase, unknown function, (encoded on structural gene a). |
|
on which genes are these enzymes encoded
|
they are encoded on the structural genes z,y and a.
|
|
Bacteria grown in the presence of this sugar it makes 5,000 of these molecules, when lacking it will synthesize 5 molecules.
|
Lactose
|
|
what is the lactose operon
|
A unit of transcription on the chromosome it consists of the same thing as an operon the structural gene of the lactose operon codes for the 3 enzymes involved in lactose uptake
|
|
A peptide bond is formed between the ___ of the amino acid in the ___ site of the ribosome and the ____ of the amino acid at the ___ site.
|
alpha-carbonyl group
"P" site Alpha-amino group "A" site |
|
True or False. During linkage of elongation, the ether bond between the tRNA in the "P" site and its amino acid is cleaved
|
False. Ester bond not Ether bond.
|
|
The peptide bond formation of elongation is formed by the bond breakage of what bond?
|
ester bond between the tRNA in the "P" site and its amino acid
|
|
True or False. The growing peptide of elongation is now two residues longer.
|
False. The growing peptide is now ONE residue longer.
|
|
the movement of ribosomes along the mRNA by one codon length is the 5' to 3' direction is called what?
|
translocation
|
|
Translocation of elongation requires what?
|
elongation factor "G", EF-G, and the hydrolysis of GTP.
|
|
Protein synthesis continues until what?
|
the ribosome reaches one of the three nonsense (termination) codons
|
|
What are the nonsense (termination) codons and where are they located.
|
UAA
UGA UAG located on the mRNA |
|
What happens in protein synthesis once a nonsense codon is read?
|
A protein release factor (RF) binds to the ribosome.
|
|
E.coli has three release factors. What is their function?
|
they hydrolyze the ester bond that holds the last tRNA that entered the ribosome.
|
|
True or False. A released protein in Termination still contains the formyl group on the methionine.
|
True
|
|
How is the formyl group on the methionine removed in termination?
|
enzymatically
|
|
True or False. Catabolite is a negative control system.
|
False. Catabolite is a positive control system.
|
|
What bacteria when grown in the presence of lactose and glucose will first use glucose becuase it represses the lactose operon?
|
E.coli
|
|
True or False. E.coli only uses lactose when the glucose is gone.
|
True
|
|
What is a growth pattern in which there are two exponential phases of growth?
|
diauxic growth
|
|
What leads to diauxic growth?
|
Catabolite Repression
|
|
How does translation of the leader sequence regulate transcription of structural genes?
|
The trp leader mRNA sequence can base pair in several alternative hairloop structures depending on the concentration of trp present.
|
|
What controls the expression of genes for trp biosynthesis?
|
trpP
trpO trpR trpL (leader) |
|
Where is trpL located?
|
between the trpO and trpE of the operon
|
|
What contains a stop signal (attenuator)?
|
trpL
|
|
What happens when trp is abundant?
|
the first part of the leader mRNA sequence is translated into a short leader sequence
|
|
Synthesis of the leader sequence when trp is abundant results in what?
|
termination of the transcription of the structural genes
|
|
What happens when trp is in short supply?
|
the leader sequence is not synthesized
|
|
What is the regulation of transcription termination?
|
attenuation
|
|
what is the operator for the lactose operon what key role does it play a part of
|
The operator is a region on the DNA that interacts with a repressor protein (coded by the regulator gene also known as the i gene)/transcription control
|
|
where is the promoter of the lactose operon
|
it is adjacent to the operator site within the operon where the RNA polymerase binds
|
|
name the genes that make up the lactose operon
|
i p o z y a
Repressor(i) operator(o) promoter(p) structural genes,z,y,a |
|
what is the role of the repressor of the lactose operon
|
The repressor attaches to the operator site and prevents binding of RNA polymerase to the promoter in the lactose operon
|
|
what inactivates the repressor protien of the lactose operon describe how it functions
|
The repressor protein is inactivated by an inducer, (a derivative of lactose will act as an inducer), the inducer attaches to the repressor protein changes its configuration so it is unable to bind to the operator
|
|
Repression is an example of what control system?
|
Negative control system
|
|
In this system the repressor protein is normally inactive and unable to bind to the operator.
|
Repression
|
|
When is the repression protein activated?
|
only in the presence of a corepressor, usually an endproduct of a biosynthetic pathway.
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What are the five structural genes of the tryptophan (trp)biosynthetic pathway?
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trpE, D, C, B, A
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The structural genes of the trp pathways are regulated by?
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trpP (promoter region)
trpO (operator region) trpR (repressor protein) |
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True or False. The repressor does not bind to the operator unless a corepressor (trp) is also present.
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True
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What happens in the absence of the corepressor (trp)?
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The RNA polymerase is able to bind to the promoter region and tryptophan is made.
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In repression, the end product tryptophan increase the affinity of what?
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the repressor protein for the operator.
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Constitutive Enzymes are produced...
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in constant amounts in the cell all the time
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Any system where the genes are continually transcribed
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inducible enzymes
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Inducible enzymes are present in what pathway?
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operon pathway
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what is the result of the inducer inactivating the repressor so that it cannot bind to the operator
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causes the repressor protien to change its strucutre
so the RNA polymerase is able to bind to the promoter region of the DNA and transcribe its structural genes within the operon. Remember lactose induces this operon. |
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what is the of Beta galactosidase in lactose metabolism
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to form glucose by cleaving lactose. The other product galactose is converted into glucose
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T/F if both glucose and lactose are present in the growth medium, the lac operon IS needed
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FALSE if both glucose and lactose are present in the growth medium the lactose operon is not needed
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When bacteria grow on glucose during the positive regulation of the lactose operon the cAMP level in the cells is _____. When bacteria are starved for carbon the cAMP level is ___.
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When bacteria grow on glucose the cAMP level in the cells is LOW. When bacteria are starved for carbon the cAMP level is HIGH.
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what requlates the activity of the lactose operon
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the cAMP level
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What is a mutation
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inheritable change in the sequence of DNA
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Organisms that have undergone mutation, phenotypic change in the organism. The original form of the organism is the wild type.
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Mutant
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what is spontaneous mutation?
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It can occur naturally, usually as the cause of errors in DNA replication
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The result of chemical or radiation impact on genes. Usually increases the mutation rate.
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Induced Mutations
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What are point mutations?
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involve a single substitution in a base. If this occurs in the third position of the codon, it is a silent mutation. No effect on the amino acid coded by the affected area of the DNA
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Substitutions in either the #1 or #2 position of the codon. Consequences vary from protein to protein.
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Missense mutations
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What are nonsense mutations
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the mutation results in the formation of a nonsense codon, this may result in premature termination of protein synthesis.
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Mutations where segments of the genome are removed.
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Deletions
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What are insertions?
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when one or more bases are added to DNA
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Single base deletions or insertions. These could completely change the amino acid sequence of the protein starting at the point of the mutation.
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Reading frameshift
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What is a back mutation?
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mutated base is changed back into its original form.
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Overcome or suppress the effects of the initial mutation without the alternation in the original gene.
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Suppressor mutations
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The following is an example of what reversible effect?
Codon changed GCU to ACU, the new codon codes for threonine instead of alanine, however if the anticodon-tRNA is also changed the effects of the original mutation are supressed. |
Supressor mutation
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True or False. Bacteria have developed different repair mechanisms to replace damaged DNA.
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True
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Corrects damage that causes distortion in the DNA helix.
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Excision repair.
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T/F the cAMP protein(CRP) is a negative regulator for the lactose operon
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False . The cAMP receptor protein (CRP), is a positive regulator for the lac operon.
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These can be used to increase the rate of mutation
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Mutagenic agents
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most Mutagenic agents are _________ and exposure to them leads to a higher incidence of ________
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carcinogens/cancer
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causes the formation of pyrimidine dimers in chromosomes
which leads to Distortion of the helix, bulges. Interference with DNA replication and transcription |
UV radiation
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the base analogs of a mutagenic agent are
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chemicals
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which chemical that is a mutagenic agent causes thymine to bond with guanine instead of adenine what does this lead to
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5-bromouracil the incorrect pairing leads to errors in replication
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some agents can cause ______ which is a replacement of a purine by a different purine or a pyrimidine for a different pyrimidine
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transistions
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other agents cause ______ which is a replacement of a purine by a different pyrimidine
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Transversions
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An alkylating agent, acts at the DNA replication fork and causes crosslinking of the DNA strands and errors in replication.
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NTG
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Method used to detect auxotrophs from the prototrophs (wild type strain)
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Replica Plating
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The following is an example of what DNA repair mechanism in bacteria?
T-T dimers from UV radiation |
Excision Repair
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UvrABC endonuclease is encoded by what three genes?
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uvrA
uvrB uvrC |
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What cuts on both sides of the damaged area in excision repair?
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uvrABC endonuclease
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The excision of uvrABC endonuclease results in the release of what?
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12 nucleotide ssDNA segments containing the damaged bases.
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What is the ssDNA gap of excision repair filled by?
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polymerase I and DNA ligase joining the fragments.
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What is the light activated enzyme in photoreactivation that cleaves the covalent linkages between damaged pyrimidines?
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photolyase
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True or False. The repair performed by photolyase does require the removal and replacement as in excision repair.
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False. It does not require removal and replacement.
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The bases in photoreactivation
are removed by what enzyme that detects and removes the unnatural base. |
glycosylases
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The resulting hole of the removed bases in photoreactivation is called an..
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AP site (apyrimidinic or apurinic) depending on the base removed
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What enzyme removes the bases of photoreactivation?
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DNA polymerase I
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What enzyme joins the fragments of photoreactivation?
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DNA ligase
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If the DNA damage is very severe, ie large gaps in the helix what repair mechanism is used?
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SOS response
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The SOS response system involves how many genes?
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17
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The 17 genes of the SOS response system are involved in...?
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in excision repair of DNA damage
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Expression of the 17 genes of the SOS response system are controlled by what genes?
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lexA, recA genes
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name the methods of transfer of genetic material in bacteria and describe them
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Transformation: insertion of naked DNA from a donor cell into a recipient cell.
Transduction: bacterial virus (phage), is the vector of the transfer of the DNA material Conjugation: bacterial DNA transfer that involves contact between a donor and recipient cell. |
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who made the discovery of transformation and what organism
did he utilize to prove it |
Griffith/Streptococcus pneumoniae
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natural transformation involving DNA occurs only in certain bacteria cells are transformable usually in what phase of growth
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the late log phase
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what is it called when a A small portion of total DNA is transferred to the recipient cell.
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Transformation
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When the recipient is in the proper physiological state to take up the DNA it is said to be
___________. this usually relates to a ______ on the recipient like low MW protein. |
competent/surface factor
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what are the two ways transformation can be carried out in the lab
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natural or artificially
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when a cell lyses a closely related recipient takes up the DNA when it is competent
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Natural transformation
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when DNA is extracted from a cell chemically. This DNA is usually purified and concentrated. The log phase-recipient cells are chemically treated with CaCl2 to make the recipient cells competent. The DNA is taken up by the recipient cells, dsDNA in Gram + bacteria is degraded to yield ssDNA transported into the cells. In Gram – bacteria, dsDNA fragments are transported into the cell but only ssDNA fragments are incorporated into the chromosome. what is this called
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Artificial transformation
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Involves the introduction of bacteriophage DNA into a cell
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Transfection
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In what transfer of genetic material do you treat cells with CaCl2, infect them with DNA that has been purified from bacteriophage?
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Transfection
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What bacterial test is used to screen for carcionogens that cause mutations in bacteria?
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Ames Test
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What test measures the reversion of histidine auxotrophs in Salmonella typhimurium to histidine prototrophs?
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Ames Test
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True or False. The Ames test involves feeding suspected carcinogens to rats, removing their livers and providing the extract to his- Salmonella typhimurium with the idea that the carcinogen will cause a mutation in the bacterial strain to allow it to grow without requiring the addition of histidine to the medium.
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True
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