Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
63 Cards in this Set
- Front
- Back
|
What is the central dogma of molecular biology?
|
genetic material in a living thing is DNA
genetic information is passed from generation to generation by a copy of the DNA information within the DNA that tells the cell how to make a specific protein copied onto a molecule of mRNA information in the mRNA is used to direct the synthesis of a protein transcription, translation, replication |
|
|
what are the roles of proteins, RNA, and DNA?
|
-enzymes are proteins
-most of the things a cell does depend on proteins -synthesis of proteins is controlled by mRNA -synthesis of RNA is directed by DNA -synthesis of DNA is directed by DNA -DNA is the storage site of genetic information |
|
|
What is semi-conservative?
|
since DNA is composed of 2 strands that have a complementary sequence, each strand can act as a template for directing synthesis of another strand
the new double stranded DNA molecules consist of one strand from the old DNA and one strand from the new DNA |
|
|
what is the enzyme that makes new DNA?
|
DNA polymerase
|
|
|
what are the materials needed for DNA replication?
|
-nucleotides
-template -primer -enzymes -origin of replication |
|
|
What nucleotides are needed for DNA replication
|
dNTPs, dATP, dGTP, dTTP
|
|
|
what is a primer?
|
short piece of DNA or RNA that binds the template and has a free end
|
|
|
what is a template?
|
preexisting strand of DNA that determines the sequence of nucleotides in the new strand
|
|
|
what enzymes are needed for DNA replication?
|
-helicase
-primase -DNA polymerase III -DNA polymerase I -DNA ligase -DNA gyrase -DNA topoisomerase |
|
|
what does helicase do.
|
separates the two strands of DNA
|
|
|
what does primase do?
|
makes the short RNA primer
|
|
|
what does DNA polymerase I do?
|
removes primers, fills in gap
|
|
|
what does DNA ligase do?
|
joins pieces of DNA
|
|
|
what does DNA gyrase do?
|
controls super twisting of DNA
|
|
|
what does DNA topoisomerase do?
|
controls super twisting of DNA
|
|
|
What is origin of replication?
|
a sequence of DNA where the enzymes of replication bind and start the process of duplication of DNA
|
|
|
explain transcription
|
when RNA is synthesized, just one strand of DNA is used as a template
the 2 strands of DNA is called sense and antisense sense strand has same sequence of mRNA; it is NOT used as the template for RNA synthesis antisense is the template for RNA and is complementary to the mRNA |
|
|
what is the transcription bubble?
|
where the strands are separated
about 20 base pairs long |
|
|
what are the three major types of RNA?
|
mRNA
rRNA tRNA |
|
|
what is mRNA?
|
messenger RNA
copy of the information in a gene that is needed to direct the synthesis of a protein consists of a sequence of codons, each specifies the incorporation of one particular amino acid single stranded molecule that is quickly degraded (1-2 mins in e.coli) |
|
|
what is rRNA?
|
ribosomal RNA
structural part of the ribosome helps to organize the 50 or so proteins that make up the ribosome and it also may be directly involved in the catalysis of reaction required in protein synthesis single stranded, but can have sections of double stranded (folded over in hairpin conformation) much more stable than mRNA due to ribosomal proteins |
|
|
what is tRNA?
|
transfer RNA
brings the correct amino acid to the ribosome and positions it in the place where it needs to be so the protein chain can grow has a clover-leaf structure due to hair pin formations anticodons- complementary to codon |
|
|
how many codons are in the genetic code?
|
64
|
|
|
explain translation
|
ribosome reads information in mRNA and with the use of tRNA molecules assembles an amino acid chain following the instructions in the mRNA chain
the process of protein synthesis in ribosomes ribosomes moves along mRNA reading codons and adding one amino acid to the peptid chain match anticodon to codon |
|
|
What is the genetic code?
|
the key for translating information which is contained within a nucleic acid sequence into information that is in the form of a protein sequence
consists of 64 codons, each sodon is a sequence of 3 nucleotides, and each condon specifies the insertion of one particular amino acid into the growing protein chain start codon = AUG stop codons =UAA, UAG, UGA |
|
|
What is the triplet codon?
Why are there 64 codons for 20 amino acids? |
if a codon was 2 letters long, there would be 16 possible codons
by adding the 3rd letter 64 codons (4x4x4) |
|
|
What does translation in bacteria, mitochondria, and chloroplasts start with?
|
N-formylmethionine
|
|
|
In eukaryotes and archaea, what does translation start with?
|
methionine
|
|
|
what encodes for methionine in bacteria and eukaryotes?
|
start codon AUG
|
|
|
What can the codon UGA encode for occastionally?
|
selenocysteine
|
|
|
What are the fundamental properties of the genetic code?
|
1. universal, with a few exceptions, it is the same in all living organisms
2. called the triplet code, it takes 3 base pairs of DNA to contain info needed to specify an amino acid 3.64 codons; 61 are called sense codons b/c they direct the incorporation of specific amino acids into a protein chain, the other 3 are nonsense codons b/c they terminate the chain 4. unambiguous, only one amino acid that a particular codon will specify 5.said to be degenerate; most amino acids can be coded for by more than one codon (6=leucine, 2=aspartic acid, 2=phenylalanine, 4=valine) 6. in not punctuated, no commas, periods, semicolons, etc |
|
|
How many amino acids are coded by only one amino acid?
|
2
methinonin = AUG tryptophan = UGG |
|
|
Where does transcription begin?
|
at the promoter
AUG near ribosome binding site |
|
|
what is a mutation?
|
stable change in the DNA of an organism that can be passed on to the offspring of that organism
permanent and rare produces a genotypic change affect the phenotype of the organism most of the time |
|
|
How does a mutation occur?
|
result from errors in DNA base pairing during replication
|
|
|
What are the 3 main characteristics of mutations?
|
rare
permanent inherited |
|
|
What are the 3 types of mutations?
|
substitution-one nucleotide is replaced by another
deletion-one or more nucleotides are left out insertion-one or more extra nucleotides are added |
|
|
What are the 3 types of codon changes that can occur due to a mutation?
|
missense mutation-encode a different amino acid, that can inactivate the enzyme
nonsense mutation-encode an early stop codon, this usually eliminates the enzyme neutral mutation-minor changes in the DNA that have no effect on an enzyme |
|
|
what is a mutagenic agent?
|
causes damage to DNA that increases the liklihood of an error being made by DNA polymerase
|
|
|
what are some common mutagens?
|
x-rays
UV light many chemicals: coal tar derivatives, LSD, DNA base analogs such as 5-bromouracil |
|
|
Do bacteria form gametes?
|
no, they do not form haploid cells, gametes or undergo meiosis
DNA exchange in bacteria is limited to the one-way transfer of DNA from a donor cell to a recipient |
|
|
what are the 3 ways that DNA can be transferred from a donor strain to a recipient strain in bacteria?
|
1.transformation
2.conjugation 3.transduction |
|
|
what is transformation?
|
naked DNA comes from a donor strain (perhaps by death and breakdown of donor strain cells) the recipient strain takes up the DNA
|
|
|
what is conjugation?
|
DNA is transferred from the donor strain to the recipient strain by direct cell to cell contact, the DNA is transferred through a narrow cytoplasmic bridge; donor cell is not killed by conjugation and in fact does not usually loose any DNA
generally involves replication of DNA that is about to be transferred and donation of one copy to the recipient cell |
|
|
what is transduction?
|
DNA from a donor cell gets incorporated into a defective virus particle called transducing phage particle; defective virus attaches to a recipient cell and injects the DNA from the donor strain
usually kills the donor strain |
|
|
What does a typical bacteria "mating" experiment require?
|
specialized donor and recipient strains
some selective media |
|
|
What is genetic recombination in bacteria?
|
intergration of foreign DNA into the genome of a recipient cell
|
|
|
what are 3 ways foreign DNA can survive in a recipient cell?
|
1. if it is an autonomous replicon; replication starts at a specific site called the origin of replication; if foreign DNA has a functional origin of replication the host can copy it
2.it intergrates into the host chromosome or another autonomous replicon such as a plasmid by homologous recombination 3.intergrates into the host chromosome or another autonomous replicon such as a plasmid by transposition |
|
|
what is an example of a autonomous replicon?
|
chromosome
plasmids temperate bacteriophages (latent virus) |
|
|
Explain transformation in bacteria?
|
genetic change produced in a bacterium that is caused by the uptake of naked foreign DNA which becomes a part of the recipient cell's genome
was discovered by griffith in 1928 |
|
|
what is a capsule?
|
important virulence factor in Streptococcus pneumonia
is a layer of polysaccharides that coats the outer surface of the cell can protect the bacterium from the defensive white blood cells of the host animal |
|
|
what did avery, macleod, and mccarty show in 1944?
|
transforming substance from the dead virulent strain to the nonvirulent strain was DNA
showed that the enzyme DNase destroyed the transforming agent but proteases did not |
|
|
what do you call a bacteria capable of picking up naked DNA?
|
competent
|
|
|
what bacteria are naturally competent?
|
Streptococcus, Staphylcoccus, Bacillus, Haemophilus, and Pseudomonas
|
|
|
when is transformation most efficient?
|
when the size of the DNA is small (1000-2000 base pairs)
with supercoiled plasmid DNA over linear DNA give recipient cell an electrical shock |
|
|
what is electroporation?
|
shocking the recipient cell with electricity to better their taking of the DNA
|
|
|
Explain conjugation in bacteria
|
DNA travels from cell to cell through a cytoplasmic bridge
sex pilus helps bacterial cells stick together so conjugation can occur mostly DNA in plasmid form plasmid is copied then transferred so donor cell doesn't loose it |
|
|
what is a sex pilus?
|
an appendage of the cell
f-pilus genes that encode for this found on f-plasmid |
|
|
what is an f+ strain?
|
has a copy of f-plasmid in its cytoplasm
will transfer genes that are on the f-plasmid |
|
|
what is an HFR strain?
|
has the f-factor intergrated into its chromosomes
will transfer chromosomal genes that are near the insertion site of the f-factor occurs in linear order disrupt the transfer by mixing in blender can tell the distance between gene and f-factor by time it takes to be transferred |
|
|
what are the steps of DNA transfer btw bacteria by generalized transducing phages?
|
bacteriophage attaches to potential host cell
virus DNA is injected into bacterial cell, bacterial enzymes make viral mRNA cellular chromosome breaks down, phage DNA is replicated, phage mRNAs and proteins are made bacteriophage particles are assembled, some accidently enclose host DNA rather than virus DNA infected cell then breaks open releasing the phage particles. defective particles that contain host cell DNA are called transducing particles. protein coat of a transducing particle protects DNA within and helps it to get into a recipient cell by the normal viral attachment and DNA injection mechanisms |
|
|
what are operons?
|
bacterial enzymes that are organized into physically linked coordinately expressed groups of genes
|
|
|
example of an operon
|
trp operon
in absence of tryptophan the repressor protein is inactive and the genes are transcribed in the presence of tryptophan the repressor is active and the genes are not expressed |
