Exam 2-Chapter 12

Question 1

Three Models for DNA Replication

Answer 1

1. conservative
2. dispersive
3. semi-conservative

Question 2

conservative model

Answer 2

original molecule is conserved
after one replication:
- one original molecule
- one entirely new molecule

Question 3

dispersive model

Answer 3

break original in fragments
with every replication you lose some of original
after one replication:
- two strands each with half of original and half of new

Question 4

semiconservative model

Answer 4

each strand serves as a template
each original strand remains intact
DNA molecule is half conserved during replication
after one replication:
- two molecules with one strand original and one strand new

Question 5

DNA replication is ____

Answer 5

semiconservative

Question 6

DNA Polymerase

Answer 6

involved in initiation of synthesis, lagging strand synthesis, recombination, and DNA repair

Question 7

DNA Replication

Answer 7

high fidelity (no errors)
once and only once per cycle (avoids re-replication)
complete (entire genome must be copied)

Question 8

DNA replication steps

Answer 8

1. double helix unwinds at origin(s) of replication
2. new polynucleotide strand synthesis by DNA polymerase

Question 9

Eukaryotic replication

Answer 9

each chromosome has numerous origins of replication
at each origin DNA unwinds creating a replication bubble

Question 10

Replication Bubble contents

Answer 10

ORC
Topoisomerase
helicase
SSBP
primer
primase

Question 11

ORC

Answer 11

Origin Recognition Complex

Question 12

Topoisomerase

Answer 12

relaxes the torsion caused by unwinding the DNA
Avoids premature helix structure

Question 13

Helicase

Answer 13

breaks H-bonds that keeps strands together
(unwinds DNA)

Question 14

SSBP

Answer 14

Single-strand binding proteins
help keep the strands separated

Question 15

primer

Answer 15

Small RNAs synthesized by primase
provides starting point for DNA synthesis

Question 16

primase

Answer 16

synthesis of short RNA sequences that are used as primers for DNA polymerase

Question 17

Replication Bubble is Bi-directional

Answer 17

DNA synthesis takes place on both strands at each end of the bubble as the replication fork proceeds outward

Question 18

New Strand synthesis

Answer 18

DNTPs add to the free 3’OH by DNA polymerase
synthesis is always in 5’-3’ direction

Question 19

DNTPS

Answer 19

DeoxyriboNucleotide TriPhosphate
building blocks of DNA
can only add to free 3’ OH- RNA primer is needed to have a free 3’ active site

Question 20

RNA polymerase

Answer 20

can start copying a template without a free 3’ OH

Question 21

primers

Answer 21

removal of RNA primers by DNA polymerase of lagging strand and then fragments are sealed by ligase
Removal of primers at the end of chromosomes leaves an unreplicated gap

Question 22

role of ligase in replication

Answer 22

seals sugar phosphate backbone

Question 23

End Replication Problem

Answer 23

becaue of RNA primer removal we would always have an unreplicated gap
Telomerase fixes this

Question 24

Telomerase

Answer 24

stretches of repetitive DNA that can extend G rich 3’ overhang

Question 25

Ribonucleoprotein

Answer 25

has both protein and RNA components

Question 26

Telomerase activity

Answer 26

proliferating cells have telomerase activity
differentiated cells in multicell org. have little to no telomerase activity
telomerase progressively shorten (aging)

Question 27

mutations affecting telomerase function cause

Answer 27

premature aging diseases