Chapter 16

Question 1

Nucleic acids are unique in their ability to direct their own replication from monomers.

Answer 1

True

Question 2

Who provided evidence that DNA can transform bacteria?

Answer 2

Frederick Griffith

Question 3

Bacterium that Griffith was studying

Answer 3

Streptococcus pneumoniae

Question 4

Streptococcus pneumoniae

Answer 4

Bacteria that causes pneumonia in mammals.

Question 5

Pathogenic

Answer 5

Disease-causing

Question 6

Nonpathogenic

Answer 6

Harmless

Question 7

Transformation

Answer 7

A change in genotype and phenotype due to the assimilation of external DNA by a cell.

Question 8

Bacteriophages (phages)

Answer 8

Viruses that infect bacteria.

Question 9

Virus structure

Answer 9

DNA enclosed by a protective coat, often protein.

Question 10

Which scientists performed experiments that showed that DNA is the genetic material of a phage?

Answer 10

Alfred Hershey
Martha Chase
They used a phage known as T2

Question 11

Antiparallel

Answer 11

Subunits run in opposite directions

Question 12

With the bases stacked just ________ apart, there are _________ in each full turn of the helix.

Answer 12

0.34 nm, ten layers of base pairs

Question 13

Purines (A and G) are about twice as wide as pyrimidines (C and T).

Answer 13

True

Question 14

Diameter of double helix

Answer 14

2 nm

Question 15

Conservative model

Answer 15

The two parental strands reassociate after acting as templates for new strands, thus restoring the parental double helix.

Question 16

Semiconservative model

Answer 16

The two strands of the parental molecule separate, and each functions as a template for synthesis of a new, complementary strand.

Question 17

Dispersive model

Answer 17

Each strand of both daughter molecules contains a mixture of old and newly synthesized DNA.

Question 18

Which scientists experiment supported the semiconservative model of DNA replication?

Answer 18

Mathew Meselson and Franklin Stahl

Question 19

The replication of a chromosome begins at particular sites called origins of replication.

Answer 19

True

Question 20

Replication fork

Answer 20

A Y-shaped region where the parental strands are being unwound.

Question 21

Helicases

Answer 21

Are enzymes that untwist the double helix at the replication forks.

Question 22

Single-strand binding proteins

Answer 22

Bind to the unpaired DNA strands, keeping them from re-pairing.

Question 23

Topoisomerase

Answer 23

Relieves the strain at the replication fork caused by the untwisting of the double helix by breaking, swiveling, and rejoining the DNA strands.

Question 24

Primer

Answer 24

The initial nucleotide chain that is produced during DNA synthesis.
Is an RNA chain and is synthesized by the enzyme primase.

Question 25

The completed primer is generally ________ long

Answer 25

5-10 nucleotides long

Question 26

The new DNA strand will start from the 3’ end of the RNA primer.

Answer 26

True

Question 27

DNA polymerases

Answer 27

Catalyze the synthesis of new DNA by adding nucleotides to a preexisting chain.

Question 28

In E. Coli, there are several different DNA polymerases, but two appear to play the major roles in DNA replication:

Answer 28

DNA polymerase III and DNA polymerase I

Question 29

DNA polymerase III

Answer 29

Adds a DNA nucleotide to the RNA primer and then continues adding DNA nucleotides complementary to the parental DNA template strand to the growing end of the new DNA strand.

Question 30

As each monomer joins the growing end of a DNA strand, two phosphate groups are lost as a molecule of pyrophosphate.

Answer 30

True

Question 31

Because of their structure, DNA polymerases can add nucleotides only to the free 3’ end of a primer or growing DNA strand, never to the 5’ end.

Answer 31

True

Question 32

Only one primer is required for DNA pol III to synthesize the entire leading strand.

Answer 32

True

Question 33

DNA polymerase III works in the direction away from the replication fork when synthesizing the lagging strand.

Answer 33

True

Question 34

Okazaki fragments

Answer 34

Segments of the lagging strand.

Question 35

DNA polymerase I

Answer 35

Replaces the RNA nucleotides of the primer.

Question 36

DNA ligase

Answer 36

Joins all the sugar-phosphate backbones of the Okazaki fragments into a continuous DNA strand.

Question 37

DNA polymerase II

Answer 37

Using parental DNA as a template, synthesizes new DNA strand by adding nucleotides to an RNA primer or a pre-existing DNA strand

Question 38

Mismatch repair

Answer 38

Other enzymes (not DNA polymerase) remove and replace incorrectly paired nucleotides that have resulted from replication errors.

Question 39

Mutations

Answer 39

Permanent changes in DNA

Question 40

Nuclease

Answer 40

DNA cutting enzyme

Question 41

Nucleotide excision repair

Answer 41

A repair system that removes and then correctly replaces a damaged segment of DNA using the undamaged strand as a guide.

Question 42

A DNA polymerase can add nucleotides only to the 3’ end of a preexisting polynucleotide.

Answer 42

True

Question 43

Two protective functions of telomeres

Answer 43

First, specific proteins associated with telomeric DNA prevent the staggered ends of the daughter molecules from activating the cell’s symptoms for monitoring DNA damage.
Second, telomeric DNA acts as a kind of buffer zone that provides some protection against the organism’s genes shortening. Telomeres postpone the erosion of genes near the ends of chromosomes.

Question 44

Telomeres become shorter during every round of replication.

Answer 44

True

Question 45

Telomerase

Answer 45

An enzyme that catalyzes the lengthening of telomeres in eukaryotic germ cells, thus restoring their original length and compensating for the shortening that occurs during DNA replication.

Question 46

More than a fifth of a histone’s amino acids are positively charged (lysine or arginine) and therefore bind tightly to the negatively charged DNA.

Answer 46

True

Question 47

Nucleosome

Answer 47

The basic unit of DNA packing; the strings between beads is called linker DNA.
Consists of DNA wound twice around a protein core of eight histones, two of each main histone types.

Question 48

Types of histones

Answer 48

H2A, H2B, H3, and H4
-H1, also.

Question 49

30-nm fiber

Answer 49

Results from interactions between the histone tails of one nucleosome and the linker DNA and nucleosomes on either side.

Question 50

Looped domains (300-nm fiber)

Answer 50

Results from loops formed by the 30-nm fiber.

Question 51

Progressive levels of DNA coiling and folding

Answer 51

-DNA, the double helix
-Histones
-Nucleosomes, or “beads on a string (10-nm fiber)
-30-nm fiber
-Looped domains (300-nm fiber)
-Metaphase chromosome

Question 52

Heterochromatin

Answer 52

The type of interphase chromatin that is visible as irregular clumps with a light microscope.

Question 53

Euchromatin

Answer 53

Less compacted, more dispersed chromatin.

Question 54

The only difference between the ATP of energy metabolism and dATP, the adenine nucleotide used to make DNA, is the sugar component, which is deoxyribose in the building block of DNA but ribose in ATP.

Answer 54

True