DNA Replication

Question 1

why is replication essential for organisms?

Answer 1

replication ensures the variance and continuity of organisms

Question 2

common characteristics of polymerases?

Answer 2

polymerase can only synthesize in the 5’ to 3’ direction and can only add nucleotides to the primer strand (cannot start new/initiate de novo)

Question 3

compare/contrast leading and lagging strand?

Answer 3

both created during dna synthesis, the leading strand follows the 5 - 3 direction of the replication fork but the lagging goes in the opposite, creating okazaki fragments

Question 4

what are primers?

Answer 4

primers are short rna strands that act as a starting point for DNA polymerase to begin synthesis

Question 5

define sliding-clamp protein

Answer 5

clamps help dna polymerase bind to and stay associated with the DNA template

Question 6

define helicase

Answer 6

proteins that unwind dna

Question 7

define dna-binding protein

Answer 7

stabilize unwound dna

Question 8

define topoisomerase

Answer 8

break and rejoin dna strands to relieve them from the tension of unwinding

Question 9

define primase

Answer 9

rna polymerase that synthesize primers

Question 10

define replisome

Answer 10

the complex of enzymes that work together during replication

Question 11

name and describe nucleotides

Answer 11

adenine + thymine
guanine + cytosine
(purines + pyrimidines)

Question 12

what does “proofreading” mean in reference to DNA polymerase?

Answer 12

it’s the process where dna polymerase ‘checks’ nucleotides and removes any incorrect matches before continuing synthesis

Question 13

how does translesion dna synthesis help decrease errors in replication?

Answer 13

it allows replication to occur across a site of damage; done by specialized DNA polymerases

Question 14

what are telomeres and why are they needed?

Answer 14

they’re non-coding sequences at the end of chromosomes that shorten over time; they signal for senescence (for the cell to stop dividing)

Question 15

how do telomeres and telomerase relate to cancer?

Answer 15

telomerase extends telomeres, so if there is a mutation in the ‘merase, then it can lead to high extension activity - tumors

Question 16

do cells always want to replicate their DNA as is?

Answer 16

no, sometimes it is better to rearrange DNA replication in order to diversify the gene pool and increase vertebrate immunity

Question 17

describe rearrangement

Answer 17

change in the structure of dna via deletion, insertion, duplication to alter the gene sequence and therefore function; occurs in b-cells

Question 18

describe somatic hypermutation

Answer 18

generates antibody diversity; mutations in variable regions, like cytosine to uracil

Question 19

describe gene amplification

Answer 19

due to repeated rounds of replication at a specific region; allows increase in genes and therefore expression of those genes