chapter 16- dna replication

Question 1

what is transformation

Answer 1

change in genotype and phenotype due to the assimilation of foreign dna

Question 2

what is a virus/bacteriophage

Answer 2

dna or rna enclosed in a protective coat made of protein

Question 3

how do viruses work

Answer 3

they infect their dna in the host cell, take over the machinery and make more viruses, the host cell bursts and releases the viruses

Question 4

what are chargaff’s rules

Answer 4

base composition of dna varies between species
[A] = [T] and [C] = [G] in all species

Question 5

how are dna strands built

Answer 5

antiparallel from 5’ to 3’

Question 6

what group is at the 3’ and 5’ ends

Answer 6

free hydroxyl at the 3’ end
free phosphate at the 5’ end

Question 7

how much space is present between the strand

Answer 7

enough for one purine and one pyrimidine (3 rings)

Question 8

what is the diameter of the helix

Answer 8

2 nm

Question 9

how many hydrogen bonds are between bases

Answer 9

adenine and thymine have 2
cytosine and guanine have 3

Question 10

what is the semi conservative model

Answer 10

when the double helix replicates each daughter molecules will have one parental strand and one newly made strand

Question 11

where does replication start

Answer 11

at specific sites called origins of replication

Question 12

what happens at origins of replication

Answer 12

two dna strands are separated and a replication bubble is formed

Question 13

what is a replication fork

Answer 13

the y shaped region at the end of the bubble where dna strands are separating

Question 14

what does the helicase do

Answer 14

enzyme that unzips the double helix at the replication forks

Question 15

what stabilizes the separated dna strands

Answer 15

single strand binding proteins

Question 16

what do topoisomerase do

Answer 16

breaks, twists and rejoins the dna strands when they are too coiled ahead of the forks

Question 17

what does primase do

Answer 17

puts down rna nucleotides to make rna primer which starts the replication strand

Question 18

how many nucleotides are present in the rna primer

Answer 18

5-10

Question 19

what enzyme elongates the new strand

Answer 19

dna polymerase

Question 20

what is the rate of elongation in human cells

Answer 20

50 nucleotides per second (slow)

Question 21

what is added to the new dna strand and what happens to it when it binds

Answer 21

nucleoside triphosphate
loses two phosphate groups as pyrophosphate

Question 22

what supplies nucleotides to dna and whats different about it

Answer 22

datp, dgtp, dctp and dttp
has deoxyribose sugar unlike atp which has ribose

Question 23

what is the difference between the leading strand and the lagging strand and why does it happen

Answer 23

leading is built continuously
lagging makes okazaki fragments that need to be joined
strand can only be built 5’ to 3’

Question 24

what joins okazaki fragments together

Answer 24

ligase enzyme

Question 25

how slow is the lagging strand

Answer 25

not much slower than leading
it has more enzymes working on it than the leading strand so it comes out about the same

Question 26

what is the difference between dna polymerase I and III

Answer 26

I removes the rna nucleotides and puts dna
III adds bases after the rna primer

Question 27

what do dna polymerase do once the strands are made

Answer 27

proofread the strands and correcting mistakes
3’ to 5’

Question 28

what happens when there is a stretch of dna that is damaged

Answer 28

nuclease will do a nucleotide excision repair

Question 29

what is a nucleotide excision repair

Answer 29

the cutting out and replacement of damaged dna

Question 30

downside to linear dna molecules (eukaryotes)

Answer 30

repeated replication shortens the ends because there is no way to complete the 5’ ends

Question 31

solution to dna shortening

Answer 31

telomeres

Question 32

what do telomeres entail

Answer 32

postponing the erosion of genes near the ends
catalyzed by telomerase in germ cells

Question 33

what is the new strand of dna called

Answer 33

daughter strand

Question 34

what is a chromatin

Answer 34

dna bound with histones

Question 35

when is dna is chromosome form

Answer 35

only during cell division
rest of the time is in chromatin form

Question 36

where do short ends happen and why

Answer 36

on lagging strands
there is no way to remove the rna primer and add dna nucleotides

Question 37

where is telomerase expressed

Answer 37

only in stem and gamete cells in eukaryotic cells

Question 38

what is a nucleosome

Answer 38

subunit of dna that is made up of dna wrapped around histone proteins