T4M2- DNA replication and mitosis

Question 1

what type of structure is DNA present in

Answer 1

helical

Question 2

what types of bonds are present between template strands

Answer 2

hydrogen bonding

Question 3

what type of model is DNA

Answer 3

semi conservative

Question 4

describe the semi conservative model for replication

Answer 4

one old and one new strand in each daughter

Question 5

who demonstrated that DNA replicates in semi conservative manner

Answer 5

Matthew Melelson and Frankin Stahl

Question 6

Describe Melelson and Stahl’s experiment

Answer 6

Cultured e coli bacteria cells for generations with nucelotide precursers with N15
- transferred bacteria to medium with N14
- extracted samples and centrifuged to separate DNA based on density

Question 7

Where was the band on the N15?

Answer 7

sat lower due to heavy density

Question 8

where was the N14 band?

Answer 8

sat higher due to lower density

Question 9

what model was ruled out

Answer 9

conservative model

Question 10

in what direction is the template strand copied

Answer 10

3’ to 5’

Question 11

in what direction does DNA synthesis occur

Answer 11

5’ to 3’

Question 12

what type of bonding is in between complementary nucleotides

Answer 12

hydrogen bonding

Question 13

what does the incoming nucleotide interact with

Answer 13

3’ hydroxyl of polymer

Question 14

what type of bond forms between new daughter strand and incoming nucleotide

Answer 14

phosphodiester bond

Question 15

where does unwinding occur and what does it separate

Answer 15

the separation of the parent strands at replication fork within origin of replication

Question 16

what does initiation require and why

Answer 16

short RNA primer- to synthesize and base pair with template DNA

Question 17

what enzyme catalyzes the polymerization of each daughter strand

Answer 17

DNA polymerase

Question 18

describe the leading strand

Answer 18

• continuous
• needs only one primer and DNA polymerase can add nucleotides to new daughter cell

Question 19

describe the lagging strand

Answer 19

• anti parallel
• has fragmented or discontinuous DNA

Question 20

in which direction does DNA synthesise in lagging strand

Answer 20

5’ to 3’

Question 21

what is formed along the lagging strands

Answer 21

okazaki fragments formed by separate primers

Question 22

what enzyme binds to parental DNA to initiate unwinding of double helix

Answer 22

DNA helicase

Question 23

what does DNA helicase do

Answer 23

breaks hydrogen bonds between base pairs

Question 24

what stabilizes DNA from rejoining after unwinding

Answer 24

single stranded binding proteins

Question 25

describe the function of topoisomerase

Answer 25

binds upstream replication fork to ease tension produced at unwinding

Question 26

role of RNA primase

Answer 26

synthesizes short RNA stretches of nucleotides complementary to parental strands

Question 27

role of DNA polymerase iii

Answer 27

does most of elongation work in prokaryotes

Question 28

role of DNA polymerase i

Answer 28

removes primer after RNA primer and replaces with nucleotides

Question 29

how many origins of replication are in prokaryotes

Answer 29

one region of replication

Question 30

what does DNA ligase do

Answer 30

joins 3' end of fragment to adjacent DNA nucleotide by catalysing phosphodiester bond, forming okazaki fragments

Question 31

what happens if the wrong nucleotide is added during replication

Answer 31

DNA polymerase replaces it

Question 32

how does replication occur in prokaryotes

Answer 32

at one site of replication- and continues in circular chromosome

Question 33

what way is elongation

Answer 33

5' to 3' end

Question 34

why can RNA primer on lagging strand not be replaced with DNA nucleotides

Answer 34

no 3' end available

Question 35

what is present at the end of linear chromosomes

Answer 35

telomers

Question 36

define telomeres

Answer 36

special sequences made of repetitions of one short nucleotide sequence

Question 37

what is the telomere sequence

Answer 37

TTAGGG

Question 38

what happens to the telomere sequence through times of replication

Answer 38

gets shorter and is used as a buffer to protect DNA- very short for the elderly

Question 39

does telomere shortening affect gametes or stem cells?

Answer 39

no- they have telomerase enzyme to catalyze lengthening

Question 40

what enzyme is a reverse transcriptase?

Answer 40

telomerase

Question 41

what type of protein is telomerase

Answer 41

ribonucleic protein

Question 42

where is DNA replicated

Answer 42

ori sites