Chapter 16 - The Molecular Basis of Inheritance

Question 1

DNA replication: synthesis of leading strand (3 steps)

Answer 1

1. helicase unwinds paternal double helix, binding protein stabilizes strands
2. RNA primer is made and leading strand is synthesized by DNA pol III
   5’ to 3
3. strand is elongated as fork continues

Question 2

DNA replication: synthesis of lagging strand (6 steps)

Answer 2

1. primase join RNA nucleotides to primer
2. DNA pol III adds nucleotides to primer forming okazaki fragment 1
3. DNA pol III detaches at next RNA primer
4. fragment 2 is primed, process repeated
5. DNA pol I replaces RNA with DNA adding nucleotides to 3’ end of fragment 1 and 2
6. DNA ligase forms a bond between new DNA and fragment 1

Question 3

helicase

Answer 3

unwinds parental double helix at replication forks

Question 4

single-strand binding protein

Answer 4

binds to and stabilizes single stranded DNA until it is used as a template

Question 5

topoisomerase

Answer 5

relieves unwinding strain ahead of replication forks by breaking, swivelling, and rejoining DNA strands

Question 6

primase

Answer 6

synthesizes an RNA primer at 5’ end of leading strand and at 5’ end of each okazaki fragment of lagging strand

Question 7

DNA pol III

Answer 7

synthesizes new DNA strand by adding nucleotides to an RNA primer or a pre-existing DNA strand

Question 8

DNA pol I

Answer 8

removes RNA nucleotides of primer from 5’ end and replaces them with DNA nucleotides

Question 9

DNA ligase

Answer 9

• joins okazaki fragments of lagging strand

- joins 3’ end of DNA that replaces primer to the rest of the leading strand

Question 10

nucleotide excision repair (DNA damage)

3 steps

Answer 10

enzymes detect and repair damaged DNA

1. nuclease cuts out and removes damaged DNA
2. repair synthesis by DNA polymerase fills in missing nucleotides
3. DNA ligase seals free end of new DNA to old DNA

Question 11

telomeres

Answer 11

postpone erosion of genes near ends of chromosomes

-shortening is connected to aging/limiting cancer growth; cell divisions)

Question 12

enzyme telomerase

Answer 12

catalyzes lengthening of telomeres in germ cells (cancer cells persist)

Question 13

DNA pol 1 (polymerase table)

Answer 13

template: DNA
product: DNA
primer: yes
direction: 5’-3’
substrate: dNTPs
proofread?: yes
frequency: 1x

Question 14

primase (polymerase table)

Answer 14

template: DNA
product: RNA
primer: no
direction: 5’-3’
substrate: NTPs
proofread?: no
frequency: 1x

Question 15

telomerase (polymerase table)

Answer 15

template: RNA
product: DNA
primer: no
direction: 5’-3’
substrate: dNTPs
proofread?: no
frequency: 1x

Question 16

RNA pol (polymerase table)

Answer 16

template: RNA
product: RNA
primer: no
direction: 5’-3’
substrate: NTPs
proofread?: no
frequency: many

Question 17

polyA (polymerase table)

Answer 17

template: none
product: RNA
primer: no
direction: 5’-3’
substrate: NTPs
proofread?: no
frequency: many

Question 18

reverse transcriptase (polymerase table)

Answer 18

template: RNA
product: DNA
primer: yes
direction: 5’-3’
substrate: dNTPs
proofread?: no
frequency: n/a