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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
genetics
This position of the codon is the most degenerate
third
The genetic code is represented by
64 possible triplets of four bases (A,G,U,C), codons
polycistronic
mRNA which has more than one cistron or gene. Encodes for several proteins
Describe the flow of genetic information
Transcription - Genetic information contained in DNA is copied into mRNA

Translation - mRNA relays information to synthesize protein molecules
This many codons code amino acids
61
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.
Many amino acids are represented by more than one codon. This means the code is:
degenerate
The total complement of genes found in a cell
genome
polycistronic mRNA is found in:
prokaryotes
The flow of information in the cell, from DNA to RNA and eventually to proteins
The Central Dogma
Typical E. coli contains ______ different genes
3000-4000
Genetic composition of an organism
genotype
codons
Four bases (A,G,U,C) arranged into 3 letter words, or triplets
There are this many possible codons
64
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
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
It states that such information cannot be transferred back from protein to either protein or nucleic acid.
The Central Dogma
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
These signal the termination of protein synthesis
UAA
UAG
UGA
UAA, UAG, UGA are called
nonsense or termination codons
nonsense codons:
signal the termination of protein synthesis
Four bases (A,G,U,C) arranged into 3 letter words, or triplets:
codons
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
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
It states that such information cannot be transferred back from protein to either protein or nucleic acid.
The Central Dogma
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
These signal the termination of protein synthesis
UAA
UAG
UGA
UAA, UAG, UGA are called
nonsense or termination codons
nonsense codons:
signal the termination of protein synthesis
Four bases (A,G,U,C) arranged into 3 letter words, or triplets:
codons
which microorganism was used in the DNA experiments
S. pneumoniae
who preformed the initial dna experiment proving dna to be the genetic material
Griffith
(s) strains of S. pneumoniae are ______while (r) strains are ____ what happened when they are both injected together
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
who preformed the experiment determing transformation of (R) to (S)
Avery, MacLeod and McCarty
material that transformed R to S
was insensitive to proteases and RNases but sensitive to DNases
Natural transformation
(or what led to transformed recipients)
DNA isolated from cells of one strain could be taken up by another
who determined the structure of dna
Watson and Crick
DNA Structure
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.
what is the ratio of nuecleotide base pairs that vary in species of bacteria
vary in proportion of G+C and A+T expressed as the mole % of G+C
what us the range in bacteria and what does a high percentage mean
range-22% to 74%
with a high percentage of G+C bonding tends to be more stable to unwinding or denaturation into single strands
what happens to DNA in spectrophotometers as it denatres
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
what kind of bonds between A+T and G+C
double bons in A+T triple Bonds in G+C
Therefore the 2 polynucleotide chains in DNA helix are
complementary (ie GCATAGC other is CGTATCG)
and anti parrallel
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
How many base pairs are in e.coli
4.7X10^6
what is the molecular whieght of the base pairs in e. coli
2.5X10^9 daltons
the chromosome molecule is how many times longer the e.colis length
550 thus the molecule is twisted and supercoiled
What individuals discovered the semiconservative model of DNA replication?
Messelson and Stahl
What isotope was used in the semiconservative model of DNA replication?
E.coli was grown with 15N as the sole nitrogen source
Describe how the semiconservative model of DNA replication was created?
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.
DNA replication is ____ and ____
sequential and bidirectional
enzymes that catalyze DNA synthesis add nulcleotides where
to the 3'-OH end of the DNA
Okazaki Fragments
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
how many different polymerases does e.coli have
3
polymerase I,II,III
all polymerases catalyze what reaction
addition of mononucleotides to the 3'-OH end of a growing polynucleotide
DNA polymerase III can polymererize how many base pairs per minute
30,000
DNA polymerase I is also called
the Kornberg enzyme
DNA polymerase I is involved in
DNA repair of UV damage this repair is excision-repair mechanism of DNA
what do all DNA polymerases require to add mononucleotides on the 3'-OH end
a preexisting polynucleotide chain
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
How was the process of DNA replication determined?
By autoradiographs by Carins, 3H-thymidine, exposed lysed cells to photographic film, revealed the shpa and replication pattern of the replicating DNA
What is theta replication?
When DNA was seen as a circular molecule with two replication forks.
What is the function of initiator proteins in DNA replication?
to recognize and bind to a specific DNA sequence of about 300 bases at the origin of replication
What happens after the initiator proteins bind at the origin of replication?
A protein complex binds to a DNA helicase, that unwinds short sections of the helix in advance of the replication fork
What assists in the DNA unwinding and rejoining of the DNA molecule?
DNA topoisomerases
The rolling circle mechanism is another mechanism for DNA replication used in what?
DNA replication in bacterial viruses; bacteriophages, and during DNA replication in conjugation
What happens in the rolling circle mechanism?
One of the strands is nicked at a specific site and the free 3’-OH end generated is extended by a DNA polymerase.
What are the three forms of RNA?
mRNA
rRNA
tRNA
How are all three forms of RNA transcribed?
from a DNA template by DNA-dependent RNA polymerase
What is the sugar found in RNA?
ribose and uracil replaces thymine
RNA polymerase is a multisubunit consisting of what enzymes?
Alpha
Beta
Beta prime
Sigma
The four subunits of RNA polymerase comprise the complete enzyme known as what?
haloenzyme
What is the initiation factor of RNA polymerase
the sigma subunit
What is the sigma subunit required for?
promoter binding
what is the largest enzyme known
and is a point of difference between the phylogenic groups
RNA polymerase
name the different phylogenic groups
Bacteria, Archaea, Eukarya.
Bacteria have how many different types of RNA polymerase with ___ different subunits
1 type with 6 different sub units
Archaea have how many different types of RNA polymerase with ___ different subunits
several types each with 8-12 different subunits.
Eukarya have how many different types of RNA polymerase with ___ different subunits
several types each with 12-14 different subunits.
What subunit dissociated from the core enzyme once polymerization begins?
Sigma subunit
What type of RNA is the most varied and comprises 5% of the total RNA?
mRNA
What is the life span of mRNA in a bacterial cell?
a few minutes
How does mRNA carry the genetic message?
from the DNA template to the ribosomes
In bacteria, mRNA commonly contains information for the amino acid sequence for several different polypeptide chains. This type of mRNA is known as what?
polycistronic mRNA
In E.coli how many enzymes are needed to synthesize histidine and are encoded in 1 mRNA molecule
ten
True of False. Not all base sequences in an mRNA molecule are translated into the amino acid sequence for polypeptides.
True
True of False. Translation starts at exactly one end of the mRNA molecule and proceeds to the other end.
False. It rarely starts at one end. It may begin 100s of nucleotides in from the 5'-p terminus.
When translation of mRNA does not start at one end (5'-p) , there is untranslated region known as what?
the leader, which is usually 5-20 bases
The polycistronic mRNA contains what type of sequences?
spacer sequences that are 10 bases long and separate the coding sequences.
What type of RNA is the smallest
tRNA
What is the structure of tRNA?
cloverleaf structure folded back on themselves
How is the unique structure of tRNA maintained?
by internal base pairing which reults in the looks
What are the modified bases of tRNA? Name two examples.
methylated forms
Examples: pseudouridine and dihydrouridine
What molecule of RNA is involved with the translation of the genetic message?
tRNA
how many types of rRNA molecules are found in prokaryotic ribosomes and what are they
3 types= 5S rRNA, 23S rRNA both found in the 50S ribosomal subunit. A 16S rRNA found in the 30S ribosomal subunit.
what is the composition of rRNA in ribosomes and what is it for protien
66% rRNA and 33% protien
the intact rRNA particle is called what in bacteria
70S ribosome
what is the role of rRNA molecules in ribosomes
they contribute to ribosome strucuture and have a functional role in protien synthesis
in bacteria the _____ pairs with the initiation sequence site on the mRNA this does what
16S rRNA, positions the mRNA on the ribosome
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
how much of the chromosomal dna encodes for the synthesis of rRNA and tRNA
less than 1%
both rRNA and tRNA are formed from _________ initially then cleaved into________
larger precursors/smaller final products
T/F both rRNA and tRNA are LESS stable than mRNA
FALSE they are more stable than mRNA
How does the bacterial cell make rRNA and tRNA ?
The molecules are excised from large primary transcripts.
____ is an adaptor of amino acids to mRNa codons at the ribosome, and incorporation into growing proteins.
tRNA
True of false. Each tRNA does not carry a specific amino acid.
False. Each tRNA does carry a specific amino acid.
What is the enzyme for the activation of amino acid-tRNA
synthetase
What is necessary to link the amino acid to the appropriate tRNA?
ATP
True of False. There is at least 1 tRNA for the 21 amino acids.
True
What loop is involved in the recognition at the ribosome in tRNA?
Anticodon loop
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
True or False. The anticodon loop contains 3 bases that are in a sequence unique for each tRNA.
True
RNA synthesis is in what direction?
5' to 3' direction of chain growth from the DNA template.
True or False. Only one of the DNA strands is transcribed in any given DNA region (coding or sense strand).
True
How does RNA synthesis begin?
With binding of RNA polymerase to a promoter DNA
What are promoters in RNA synthesis?
specific DNA sequences, usually 20-200 bases long
DNA sequences that serve as promoters for the RNA polymerases are?
-Pribnow box, sequence (TATAAT), (-10 sequence)
- -35 sequence, sequnce (TTGACA)
What sequence is found as part of all prokaryotic promoters?
TATAAT
The TTGACA sequence is located where?
about 35 base pairs upstream from the polymerization start site
In E. coli, rRNA transcripts contain ___ copy of each of 5S,16S, and 23S rRNA as well as __ different tRNA molecules.
one copy of and 4 different
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
T/F RNases produce the modified bases in tRNA
false other enzymes produce the modified bases in tRNA
during RNA synthesis what happens to the area behind the core polymerase
the area reanneals and the new RNA dissociates fro the DNA template
what is a termination sequence do
Termination sequences (several have been identified), cause the RNA polymerase to pause and terminate RNA synthesis
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
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.
What do TATAAT and TTGACA sequences do?
They instruct RNA polymerase where to start synthesis.
True of False. The strength of the binding of the RNA polymerase to different promoters varies greatly.
True
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.
Where does RNA synthesis begin?
with the binding of the RNA polymerase to the promoter, which causes the DNA strands to separate.
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.
True or False. In RNA synthesis only one turn of the DNA molecule is unwound at a time.
True
When are ribonucleotides added during RNA synthesis?
after 8-10 base pairs are added to the growing chain
What mediates elongation in RNA synthesis?
The core enzyme which is yielded from the sigma factor dissociating from the haloenzyme.
True or False. Different sigma subunits have been determined for different bacteria.
True
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.
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
The initiation complex is formed from
the binding of the 30S ribosomal subunit to the initiation codon, AUG or GUG on the mRNA.
what percent of all proteins in E.coli begin with methionine.
45%
The initiation codon establishes what
the reading frame for the mRNA.
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
what follows An initiator tRNA carrying fmet pairs with the initiation codon in the presence of the 30S ribosomal subunit
shine delgarno sequence
what is the Shine Delgarno sequence
a purine rich region (3-9 bases) that precedes the 5’ end of the initiating AUG codon
what is the role of the Shine Delgarno sequence
it specifies the ribosomal binding site on the mRNA.
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.
what is the purpose of the protien initiation factor IF3
catalyzes the dissociation of the 70S ribosome into individual subunits
what other purpose does IF3 serve
IF3 is also associated with the binding of the 30S subunit to the appropriate site of the mRNA.
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.
what does IF1 do
IF1 assists the IF3 in binding to the 30S subunit to the mRNA.
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.
name the two categories of regulation
negative regulation and positive regulation.
what happens during negative regulation
In negative regulation, an inhibitor is present in the cell and transcription is prevented
what is the inhibitor present in negative regulation
The inhibitor is called a repressor
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.
What are the five structural genes of the tryptophan (trp)biosynthetic pathway?
trpE, D, C, B, A
The structural genes of the trp pathways are regulated by?
trpP (promoter region)
trpO (operator region)
trpR (repressor protein)
True or False. The repressor does not bind to the operator unless a corepressor (trp) is also present.
True
What happens in the absence of the corepressor (trp)?
The RNA polymerase is able to bind to the promoter region and tryptophan is made.
In repression, the end product tryptophan increase the affinity of what?
the repressor protein for the operator.
Constitutive Enzymes are produced...
in constant amounts in the cell all the time
Any system where the genes are continually transcribed
inducible enzymes
Inducible enzymes are present in what pathway?
operon pathway
what is the result of the inducer inactivating the repressor so that it cannot bind to the operator
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.
what is the of Beta galactosidase in lactose metabolism
to form glucose by cleaving lactose. The other product galactose is converted into glucose
T/F if both glucose and lactose are present in the growth medium, the lac operon IS needed
FALSE if both glucose and lactose are present in the growth medium the lactose operon is not needed
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 ___.
When bacteria grow on glucose the cAMP level in the cells is LOW. When bacteria are starved for carbon the cAMP level is HIGH.
what requlates the activity of the lactose operon
the cAMP level
What is a mutation
inheritable change in the sequence of DNA
Organisms that have undergone mutation, phenotypic change in the organism. The original form of the organism is the wild type.
Mutant
what is spontaneous mutation?
It can occur naturally, usually as the cause of errors in DNA replication
The result of chemical or radiation impact on genes. Usually increases the mutation rate.
Induced Mutations
What are point mutations?
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
Substitutions in either the #1 or #2 position of the codon. Consequences vary from protein to protein.
Missense mutations
What are nonsense mutations
the mutation results in the formation of a nonsense codon, this may result in premature termination of protein synthesis.
Mutations where segments of the genome are removed.
Deletions
What are insertions?
when one or more bases are added to DNA
Single base deletions or insertions. These could completely change the amino acid sequence of the protein starting at the point of the mutation.
Reading frameshift
What is a back mutation?
mutated base is changed back into its original form.
Overcome or suppress the effects of the initial mutation without the alternation in the original gene.
Suppressor mutations
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
True or False. Bacteria have developed different repair mechanisms to replace damaged DNA.
True
Corrects damage that causes distortion in the DNA helix.
Excision repair.
T/F the cAMP protein(CRP) is a negative regulator for the lactose operon
False . The cAMP receptor protein (CRP), is a positive regulator for the lac operon.
These can be used to increase the rate of mutation
Mutagenic agents
most Mutagenic agents are _________ and exposure to them leads to a higher incidence of ________
carcinogens/cancer
causes the formation of pyrimidine dimers in chromosomes
which leads to Distortion of the helix, bulges. Interference with DNA replication and transcription
UV radiation
the base analogs of a mutagenic agent are
chemicals
which chemical that is a mutagenic agent causes thymine to bond with guanine instead of adenine what does this lead to
5-bromouracil the incorrect pairing leads to errors in replication
some agents can cause ______ which is a replacement of a purine by a different purine or a pyrimidine for a different pyrimidine
transistions
other agents cause ______ which is a replacement of a purine by a different pyrimidine
Transversions
An alkylating agent, acts at the DNA replication fork and causes crosslinking of the DNA strands and errors in replication.
NTG
Method used to detect auxotrophs from the prototrophs (wild type strain)
Replica Plating
The following is an example of what DNA repair mechanism in bacteria?
T-T dimers from UV radiation
Excision Repair
UvrABC endonuclease is encoded by what three genes?
uvrA
uvrB
uvrC
What cuts on both sides of the damaged area in excision repair?
uvrABC endonuclease
The excision of uvrABC endonuclease results in the release of what?
12 nucleotide ssDNA segments containing the damaged bases.
What is the ssDNA gap of excision repair filled by?
polymerase I and DNA ligase joining the fragments.
What is the light activated enzyme in photoreactivation that cleaves the covalent linkages between damaged pyrimidines?
photolyase
True or False. The repair performed by photolyase does require the removal and replacement as in excision repair.
False. It does not require removal and replacement.
The bases in photoreactivation
are removed by what enzyme that detects and removes the unnatural base.
glycosylases
The resulting hole of the removed bases in photoreactivation is called an..
AP site (apyrimidinic or apurinic) depending on the base removed
What enzyme removes the bases of photoreactivation?
DNA polymerase I
What enzyme joins the fragments of photoreactivation?
DNA ligase
If the DNA damage is very severe, ie large gaps in the helix what repair mechanism is used?
SOS response
The SOS response system involves how many genes?
17
The 17 genes of the SOS response system are involved in...?
in excision repair of DNA damage
Expression of the 17 genes of the SOS response system are controlled by what genes?
lexA, recA genes
name the methods of transfer of genetic material in bacteria and describe them
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.
who made the discovery of transformation and what organism
did he utilize to prove it
Griffith/Streptococcus pneumoniae
natural transformation involving DNA occurs only in certain bacteria cells are transformable usually in what phase of growth
the late log phase
what is it called when a A small portion of total DNA is transferred to the recipient cell.
Transformation
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
what are the two ways transformation can be carried out in the lab
natural or artificially
when a cell lyses a closely related recipient takes up the DNA when it is competent
Natural transformation
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
Artificial transformation
Involves the introduction of bacteriophage DNA into a cell
Transfection
In what transfer of genetic material do you treat cells with CaCl2, infect them with DNA that has been purified from bacteriophage?
Transfection
What bacterial test is used to screen for carcionogens that cause mutations in bacteria?
Ames Test
What test measures the reversion of histidine auxotrophs in Salmonella typhimurium to histidine prototrophs?
Ames Test
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.
True