DNA replication

Question 1

Watson and Crick proposed structure of DNA allowed the molecule to be ____. Each parent strand serves as the ____ to line up the bases for the synthesis of a new daughter strand. Each new DNA helix consists of one strand from the parent helix and one newly synthesized ____strand

Answer 1

replicated. Template. daughter

Question 2

The structure of DNA accounts for ___ and ___ of genetic information

Answer 2

storage; transmission

Question 3

Meselson and Stahl proved that DNA replication is semiconservative:

Answer 3

One strand stays the same and serves as a template for the other strand. Other strand is made via complementary pairing of incoming nucleotides to the parent template strand.

Question 4

How did Meselson & Stahl prove that DNA replication is semiconservative?

Answer 4

Grew E. coli for many generations in media containing N15 heavy isotope. They then transferred cells to N14 media and grew for successive generations and took sample for each generation time (cell doubling) and analyzed DNA density.

Question 5

What was Meselson and Stahls technique?

Answer 5

Before transfer to media DNA had a high density. DNA after 1 gen had a density exactly in bet all N15 and all N14. After a second cell div. half of the DNA is all N14 labeled and half has the intermediate density which rules out non conservative replication which would have given all the DNA at a density 1/4 bet light and heavy

Question 6

What is Kornberg known for

Answer 6

First to isolate DNA polymerase I from E. coli from nucleotide triphosphate precursors: dGTP, dATP, dCTP, and dTTP

Question 7

what is Cairns known for

Answer 7

found out that replicating DNA has an extra loop (theta). DNA replication is bidirectional!

Question 8

DNA polymerase exhibits processivity. What is processivity?

Answer 8

how long it stays on the template and adds bases before DNA polymerase enzyme dissociates from the template.

Question 9

Polymerization is ____favored: hydrolysis of PPi and base pairing + stacking

Answer 9

thermodynamically

Question 10

DNA polymerases are very ____. Sev mechanisms reduce error rate, such as mismatch repair mechanisms

Answer 10

accurate

Question 11

how to errors in replication occur

Answer 11

protons form abnormal arrangements of e- that change the pairing ch’s of specific bases.

Question 12

What is the mechanism of recognizing a tautomer

Answer 12

proofreading nuclease moves backwards and cuts base out. Polymerase resumes

Question 13

DNA polymerase I has a ___function. DNA polymerase II has a specialized repair function. DNA polymerase III is the main DNA _____enzyme.

Answer 13

repair; replication.

Question 14

DNA pol III has ___ subunits and ____ processivity

Answer 14

> 10; 500,000

Question 15

What are the 3 stages of DNA replication

Answer 15

1. Initiation (most complicated)
2. Elongation
3. Termination

Question 16

DNA replication begins at the _____. It has DUE that has ____bp seq element which unwinds and form ss pieces that can be stabilized and start process of replication.

Answer 16

ORI; 13

Question 17

THere are ____ R regions which are binding sites for DNA a protein which constrains the DUE. This causes it to open up into ss portions.

Answer 17

5

Question 18

what are the proteins required to initiate replication at the E. coli origin

Answer 18

1. DNA a: recognizes ori
2. DNA b: helicase that unwinds DNA
3. DNA c: Req for DNA b binding at origin (helper protein)
4. HU: histonelike protein
5. DNA G: synthesizes RNA primers. (Primase)
6. SSB: binds single stranded DNA
7. DNA gyrase: relieves torsional strain gen by DNA unwinding
8. Dam methylase: methylates 5’ GATC seq at ori

Question 19

what is the lagging strand

Answer 19

makes DNA seq piece meal in Okazaki fragment

Question 20

How does replication initiate

Answer 20

1. dnaA binds to oriC and forms initial complex
2. dnaB/dnaC dimers bind to open complex and unwind origin DNA to expose ss template.
3. ss DNA stabilized by binding of SSB’s

Question 21

what is considered the prepriming complex

Answer 21

dnaA dnaB/dnaC

Question 22

all synthesizing Dna polymerases require a ____ and can only add to the ____ end

Answer 22

primer; 3’ end of an existing strand.

Question 23

____binds to dnaB/dnaC on DNA template. Other proteins add to form complex called the _____. Then a ______ dimer now binds to primosome to form the replisome. Leading strand synthesis begins at each fork using one DNA pol III molecule, the RNA primer and the leading strand template.

Answer 23

Primase; primosome; DNA pol III

Question 24

what is primase

Answer 24

a specialized RNA pol that synthesizes a short 15 nt strech of RNA on DNA template which remains base paired.

Question 25

DNA polymerases add bases to ____ hydroxyl end

Answer 25

3'

Question 26

Physical dir of movement of replication fork on one strand in same direction as synthesis which is:

Answer 26

5' to 3'

Question 27

The new daughter strand is the ____strand. physical direction in the opposite direction to synthesis is for the other daughter strand.

Answer 27

daughter

Question 28

solution to leaving long stretches of ss DNA is to syntheize ____strand discontinuously in short stretches called okazaki fragments

Answer 28

lagging

Question 29

____ ____ and topoisomerase I maintain the chromosome negatively supercoiled.

Answer 29

DNA gyrase

Question 30

how is elongation initiated

Answer 30

lagging strand is looped around on replisome so small portion of it is in same orientation as the leading strand which is how we get primers added on.

Question 31

DNA polymerase I and ____ ___ repair the okazaki fragments and produce a discontinuous DNA lagging strand

Answer 31

DNA ligase

Question 32

how does dna replication terminate?

Answer 32

Replication forks meet. Topoisomerases allow two double helices to sep

Question 33

How is DNA replication in eukaryotes?

Answer 33

much more complex. Have 5 polymerases instead of 3

Question 34

Whats the diff between bacterial and human DNA replication

Answer 34

1. Linear chromosomes 2. Multiple ori's 3. more DNA polymerases

Question 35

what are the DNA polymerases in eukaryotes

Answer 35

1. alpha: primase 2. betta: base excision repair and meiotic recombination 3. gamma: mitochondrial replication 4. delta: nuclear replication, NER & MMR 5. epsilon: nuclear replication, NER and MMR

Question 36

what are telomeres

Answer 36

the ends of eukaryotic chromosomes; allow linear molecules to be replicated w/o loss of information. contain hundreds of tandem repeated copies of a GT rich seq.

Question 37

How are telomeres synthesized?

Answer 37

Through enzyme telomerase which is a specialized reverse transcriptase bc using an RNA template to make a DNA copy. It has an RNA component that serves as a template for the synthesis of a repetitive GT rich DNA seq ch. of each organism.

Question 38

Priming can occur in the ____ not the coding DNA

Answer 38

telomere

Question 39

what are functions of telomeres.

Answer 39

1. SEal chromosomal ends 2. Attach chromosomes to nuclear envelope 3. facilitate replication 4. Serve as mitotic clock: - shorter telomeres induce senescence/apoptosis - no detectable telomerase act in diff cells. - telomerase is active in germs cells, stem cells and tumors - telomeres in fibroblasts from elderly patients are shorter than those from children.