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;
20 Cards in this Set
- Front
- Back
|
Define transformation
|
incorporation of external DNA into bacterial cell
|
|
|
How did Griffith’s experiments show that there was a hereditary factor?
|
showed transformation of bacteria R vs S strains. substance was passed onto offspring. some sort of hereditary factor.
|
|
|
Describe the Avery et al experiments and how they demonstrated that DNA was the
transforming factor? |
-heat killed streptococcus cells,
-removed lipids and carbohydrates. -add enzyme to digest one type of macromlecule protein/dna/rna. -3 treatments to a mixture of r cells. -transformation did not occur when dna was killed. |
|
|
Describe the Hershey-Chase experiments. Why did they use viruses? How could they
distinguish between the DNA and protein hypothesis? |
-grow viruses in presence of 32P and 35S only.
-Proteins incorporate S not P -DNA incorporates P not S -wanted to determine if protein or DNA entered host cells and produced more viruses -add viruses with labeled DNA to separate Ecoli cultures -separate viral coats from bacterial cells -centrifuge to force cells into pellets -rad DNA in pellet, viral genes consist of DNA, viral coat of protein |
|
|
What were the 3 options for DNA replication and how did they differ?
|
Semiconservative - one strand serves as template for a new one
conservative - both strands serve as template then bind back dispersive - old dna cut into pieces, new and old dna intermingle |
|
|
Describe the Meselson-Stahl experiment and how it distinguished between the 3
options for DNA replication. What would you see after 1, 2, 3 or 4 generations? What replication models could be eliminated after the 1, 2, 3 or 4 generations? |
-grow Ecoli in 15N.
-transfer cells to medium with 14N -After samples divide once collect sample -After cells divice twice collect sample -Centrifuge and compare locations of DNA bands -After 1 gen semiconservative and dispersive = hybrid, conservative = 2 bands (eliminate) -After 2 gen semiconservative = 1/2 low density DNA and 1/2 intermediate, dispersive = one density (eliminate), conservative - 1/4 high density and 3/4 low density |
|
|
What is DNA polymerase and what direction does it add nucleotides to the growing
chain? |
enzyme that polymerases dNTPs to DNA. 5 -> 3
|
|
|
What is the origin of replication and how do they differ in prokaryotes versus
eukaryotes? |
where replication is initiated
prokaryote = one origin eukaryotic = multiple origins |
|
|
Define a replication fork
|
Y shaped region where parent DNA double helix is split into two strands
|
|
|
What are the key enzymes and proteins involved in opening the DNA? What do they do?
|
Topoisomerase -relieves twisting forces
Helicase - opens double helix Singe-stranded DNA-binding proteins (SSBP) stabilize the single strands |
|
|
How is the leading strand synthesized?
|
1. DNA opened, unwound, and primed
2. Continous synthesis begins with rna pol 3 and sliding clamp |
|
|
How is the lagging strand synthesized?
|
1. DNA opened, unwound, and primase makes a primer
2. DNA pol III 5->3 makes Okazaki fragments 3. DNA pol I removes primer, replaces it with dNTP's 4. DNA ligase closes gap, catalyzes phosphodiester bond b/w adjacent fragments |
|
|
What is an Okazaki fragment?
|
short segment of dna produced during replication of lagging strand
|
|
|
What proteins are involved in both leading and lagging strand synthesis? What
proteins are involved in just lagging strand synthesis? |
Primase, topoisomerase, helicase, single stranded binding proteins, dna pol III, dna pol I, dna ligase, sliding clamp
dna ligase, dna pol I |
|
|
Define a telomere
|
end of chromosome, not copied on lagging strand, do not contain genes, repeating bases
|
|
|
What is the distinction between DNA replication of the leading and lagging strand at
the telomeres? |
lagging strand has no room for primer at the end, end is replicated by telomerase
|
|
|
How is a telomere replicated and how is this different from replication of the rest of
the DNA? |
1. strand of DNA has no room for primer
2. Telomerase binds and adds dNTPs from RNA to the end of the DNA 3. Telomerase moves down the DNA and adds base repeats 4. primase, dna pol I & III, ligase synthesize lagging strand |
|
|
How does DNA polymerase proofread? Why does it need to proofread?
|
DNA pol II 3->5 exonuclease activity. looks for bases with no H bonds to complementary strands. proofreads to reduce mistakes
|
|
|
What is a mistmatch? What is a thymine dimmer?
|
not properly matched bases. when uv rays strike dna with adjacent thymine dimers it can cause the two dimers to bond to each other. causes kink in dna
|
|
|
Describe mismatch and nucleotide excision repair
|
mismatch = mismatched bases are fixed with proteins
nucleotide excision = defective + sorrounding bases are removed and replaced using dna pol and dna ligase |
