CHAPTER 11_DNA Replication and Recombination

Question 1

how many base pairs exist within the human genome

Answer 1

3 Billion

Question 2

which experiment grew E. coli cells for many generations in a medium that had ^15NH4Cl (ammonium chloride) as the only nitrogen source

Answer 2

Meselson-Stahl experiment

Question 3

Samples are forced by centrifugation through a density gradient of a heavy metal salt, such as cesium chloride. Molecules of DNA will reach equilibrium when their density equals the density of the gradient medium

Answer 3

sedimentation equilibrium centrifugation (buoyant density gradient centrifugation)

Question 4

J. Herbert Taylor, Philip Woods, and Walter Hughes presented evidence that semiconservative replication also occurs in eukaryotic organisms. They experimented with root tips of the broad bean _______

Answer 4

Vicia faba

Question 5

J. Herbert Taylor, Philip Woods, and Walter Hughes were able to monitor the process of replication by labeling DNA with _____, a radioactive precursor of DNA, and by performing ______

Answer 5

^3H-thymidine
autoradiography

Question 6

______ is a common technique that, when applied cytologically, pinpoint the location of a radioisotope in a cell

Answer 6

Autoradiography

Question 7

a chemical derived from the crocus plant that poisons the spindle fibers

Answer 7

Colchicine

Question 8

_______ creates two replication forks that migrate farther and farther apart as replication proceeds

Answer 8

Bidirectional replication

Question 9

These forks eventually merge, as semiconservative replication of the entire chromosome is completed, at a termination region, called ___

Answer 9

ter

Question 10

two major requirements for in vitro DNA synthesis under the direction of DNA polymerase I:

Answer 10

1. All 4 deoxyribonucleoside triphosphates (dNTPs)
2. Template DNA

Question 11

a mutant strain of E. coli that was deficient in polymerase I activity. The mutation was designated ____

Answer 11

polA1

Question 12

Although none of the three polymerases can initiate DNA synthesis on a template, all 3 can elongate an existing DNA strand, called a _____

Answer 12

primer

Question 13

polymerase I is present in greater amounts than is polymerase III, and it is also much more stable

Question 14

Its 3′ to 5′ exonuclease activity also provides a proofreading function that is activated when it inserts an incorrect nucleotide

Question 15

_____ is believed to be responsible for removing the primer, as well as for the synthesis that fills gaps produced after this removal.

Answer 15

DNA Pol I

Question 16

_____, which imparts the catalytic function to the holoenzyme

Answer 16

core enzyme

Question 18

pairs with the core enzyme and facilitates the function of a critical component of the holoenzyme, called the sliding DNA clamp

Answer 18

sliding clamp loader

Question 19

oriC, it consists of ____ DNA base pairs and is characterized by five repeating sequences of 9 base pairs, and three repeating sequences of 13 base pairs, called ________

Answer 19

245
9mers and 13mers

Question 20

initiator protein, called ___________, is responsible for initiating replication by binding to a region of 9mers.

Answer 20

DnaA (because it is encoded by the dnaA gene)

Question 21

_____ (made up of multiple copies of the DnaB polypeptide). —– is assembled as a hexamer of subunits around one of the exposed single-stranded DNA molecules. The —- subsequently recruits the holoenzyme to bind to the newly formed replication fork to formally initiate replication, and it then proceeds to move along the ssDNA, opening up the helix as it progresses.

Answer 21

DNA helicase

Question 22

Helicases require energy supplied by the hydrolysis of ATP

Question 23

base pairing must be inhibited until it can serve as a template for synthesis. This is accomplished by proteins that bind specifically to single strands of DNA, appropriately called _____

Answer 23

single-stranded binding proteins (SSBs)

Question 24

supercoiling can be relaxed by ______, a member of a larger group of enzymes referred to as DNA topoisomerases

Answer 24

DNA gyrase

Question 25

Together, the DNA, the polymerase complex, and associated enzymes make up an array of molecules that initiate DNA synthesis and are part of what we have previously
called the ______

Answer 25

replisome

Question 26

Synthesis of the RNA is directed by a form of RNA polymerase called ______, which is recruited to the replication fork by DNA helicase, and which does not require a free 3′ end to initiate synthesis

Answer 26

primase

Question 27

DNA Pol I removes the primers and replaces the missing nucleotides. Joining the fragments is the work of another enzyme, _______, which is capable of catalyzing the formation of the phosphodiester bond that seals the nick between the discontinuously synthesized strands

Answer 27

DNA ligase

Question 28

After the synthesis of ____nucleotides, the monomer of the enzyme on the lagging strand will encounter a completed Okazaki fragment

Answer 28

1000 to 2000

Question 29

This process, called ______, increases the fidelity of synthesis by a factor of about 100

Answer 29

proofreading

Question 30

Many other mutations interrupt or seriously impair some aspect of replication, such as the ligase-deficient and the proofreading-deficient mutations mentioned previously. Because such mutations are lethal ones, genetic analysis frequently uses _____, which are expressed under one condition but not under a different condition.

Answer 30

conditional mutations

ex. temperature-sensitive mutation

Question 31

This method allows one to eliminate a particular gene in a specific organ instead of the whole animal

Answer 31

conditional knockout approaches

Question 32

Eukaryotic replication origins not only act as sites of replication initiation, but also control the timing of DNA replication. These regulatory functions are carried out by a complex of more than 20 proteins, called the ______, which assembles at replication origins

Answer 32

prereplication complex (pre-RC)

Question 33

In the early G1 phase of the cell cycle, replication origins are recognized by a six protein complex known as an ______, which
tags the origin as a site of initiation of replication

Answer 33

origin recognition complex (ORC)

Question 34

_____, a term that refers to the strength of the association between the enzyme and its substrate

Answer 34

processivity

Question 35

The assembly of new nucleosomes is carried out by ______ that move along with the replication fork

Answer 35

chromatin assembly factors (CAFs)

Question 36

Telomeric sequence in humans

Answer 36

5’ - TTAGGG - 3’