chapter 15

Question 1

What is the advantage of multiple origins or replication (DNA)? disadvantage?

What domain of organism uses multiple origins of replication?

Answer 1

allows faster replication, repair and making new things. can make mistakes

archaea

Question 2

if a cell lost the ability to provide single- stranded binding proteins, how would that mess with the process of DNA

Answer 2

The DNA would snap back close because the the hydrogen bonds, so no replication

Question 3

if a cell lost the ability to produce ligase, how would that mess with DNA replication?

Answer 3

The nitrogenous bases would be missing phosphodiester bonds and there would just be fragments of DNA

Question 4

explain why the ends of every DNA molecule become shorter with every replication. How is this problem solved temporarily

Answer 4

solve it by using telomers which are made of unused dna

Question 5

which kinds of cells have a way to rebuild lost ends? What is the enzyme called

Answer 5

gametes

telomerase

Question 6

using the idea of how a virus works, explain how we know DNA is a hereditary molecule.

Answer 6

because the viruses can incorporate their DNA into your DNA

Question 7

Why is there always a leading and a lagging strand while replicating DNA

Answer 7

has to synthesize from 3’ to 5’, away from replication fork

Question 8

why is DNA semiconservative

Answer 8

suggests that, after DNA replication,
the new DNA duplex consists of one old strand (parental) and one
new strand (daughter).

Question 9

where does dna replication begin and what does this cause

Answer 9

begins at special sites called origins of replication where the 2 DNA strands are separated, opening up a replication bubble

Question 10

what is DNA helicase

Answer 10

enzymes that separate the two strand of the double helix at the replication forks

Question 11

what is single-strand DNA binding protein

Answer 11

bind to and stabilize single stranded DNA until it can be used as a template

Question 12

topoisomerase who is this bitch

Answer 12

corrects “overwinding” ahead of the replication forks by breaking, swiveling and rejoining DNA strands

Question 13

describe DNA polymerases

Answer 13

enzymes called DNA polymerases catalyze the elongation of a new DNA at the replication fork

Question 14

what does DNA polymerase need

Answer 14

needs a primer and DNA template strand

Question 15

can DNA polymerase initiate the synthesis of a polynucleotide

Answer 15

no, it cannot initiate the synthesis of a polynucleotide they can only add nucleotides to the 3’ end of a polynucleotide

Question 16

what is the initial nucleotide stand?

Answer 16

is a short RNA primer The RNA primer is short and the 3’ end serves as the starting point for the new DNA strand.

Question 17

what does primase do

Answer 17

can start an RNA chain from scratch and adds RNA nucleotides one at a time using the parental DNA as a template

Question 18

what are the 3 components of a nucleotide

Answer 18

nitrogenous base, pentose sugar and phosphate group

Question 19

how are nucleotides added to growing DNA stands

Answer 19

Each nucleotide that is added to a
growing DNA strand starts as a
nucleoside triphosphate.
o e.g., dATP supplies
__adenine__ to DNA.

Question 20

What is the difference between ATP and dATP?

Answer 20

d says instead of ribose using deoxyribose

Question 21

name 3 other nucleoside triphosphates that are used to synthesize DNA

Answer 21

dGTO,dCTP, dTTP

Question 22

how is DNA built vs how is it read

Answer 22

build 5 to 3 but read 5’ to 3’

Question 23

what happens when a monomer of dATP joins the DNA strand?

Answer 23

the monomer loses two phosphate groups as a molecule of pyrophosphate
- subsequent hydrolysis of pyrophosphate is coupled with exergonic reactions that help drive the polymerization reaction.

Question 24

which way does DNA grow

Answer 24

DNA polymerase add nucleotides only to the 3’ end of a growing strand; therefore a new DNA strand can elongate only in the 5’ to 3’ direftion

Question 25

leading vs lagging stand

Answer 25

leading strand moves continuously towards the replication fork.
DNA polymerase III must work away from the replication fork.

Lagging stand made of series of segments called okazaki fragments that are joint together by DNA ligase

Question 26

what are the limitation of DNA polymerase in linear DNA

Answer 26

The usual replication
machinery provides no
way to complete the 5’
ends, so repeated rounds
of replication produce
shorter DNA molecules.

Question 27

function of telomeres

Answer 27

do not prevent the shortening of DNA molecules, but they do postpone the erosion genes near the ends of DNA molecules