Chapter 16

Question 1

transformation

Answer 1

the process by which a cell in culture acquires the ability to divide indefinitely, similar to the division of cancer cells

Question 2

bacteriophage

Answer 2

a virus that infects bacteria; also called phage

Question 3

virus

Answer 3

an infectious particle incapable of replicating outside a cell, consisting of an RNA or DNA genome surrounded by a protein coat (capsid), and some by a membranous envelope

Question 4

antiparallel

Answer 4

referring to the arrangement of the sugar-phosphate backbone in a DNA double helix (run in opposite 5’ to 3’ directions)

Question 5

DNA replication

Answer 5

DNA molecule is copied

Question 6

semiconservative model

Answer 6

type of DNA replication in which the replicated double helix consists of one old strand, derived from the parental molecule, and one newly made strand

Question 7

origin of replication

Answer 7

site where the replication of a DNA molecule begins, consisting of a specific sequence of nucleotides

Question 8

replication fork

Answer 8

a y-shaped region on a replicating DNA molecule where the parental strands are being unwound and new strands are being synthesized

Question 9

helices

Answer 9

an enzyme that untwists the double helix of DNA at replication forks, separating the two strands and making them available as template strands

Question 10

single-strand binding protein

Answer 10

a protein that binds to the unpaired DNA strands during DNA replication, stabilizing them and holding them apart while they serve as template for the synthesis of complementary strands of DNA

Question 11

topoisomerase

Answer 11

a protein that breaks, swivels, and rejoins DNA strands, helps relieve strain in the double helix ahead of the replication fork during DNA replication

Question 12

primer

Answer 12

a short polynucleotide with a free 3’ end, bound by complementary base pairing to the template strand and elongated with DNA nucleotides during DNA replication

Question 13

primase

Answer 13

an enzyme that joins RNA nucleotides to make a primer during DNA replication, using the parental DNA strand as a template

Question 14

DNA polymerase

Answer 14

enzyme that catalyzes the elongation of new DNA (eg. at a replication fork) by the addition of nucleotides to the 3’ end of an existing chain

Question 15

leading strand

Answer 15

the new complementary DNA strand synthesized continuously along the template strand toward the replication fork in the 5’ to 3’ direction

Question 16

lagging strand

Answer 16

a discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in the 5’ to 3’ direction away from the replication fork

Question 17

Okazaki fragments

Answer 17

a short segment of DNA synthesized away from the replication fork on a template strand during DNA replication; many segments are joined together to make up the lagging strand of newly synthesized DNA

Question 18

DNA ligase

Answer 18

a linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3’ end of one DNA fragment (eg. an Okazaki fragment) to the 5’ end of another DNA fragment (eg. a growing DNA chain)

Question 19

mismatch repair

Answer 19

the cellular process that uses specific enzymes to remove and replace incorrectly paired nucleotides

Question 20

nuclease

Answer 20

an enzyme that cuts DNA or RNA, either removing one or a few bases or hydrolyzing the DNA or RNA completely into its component nucleotides

Question 21

nucleotide excision repair

Answer 21

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

Question 22

telomere

Answer 22

the tandemly repetitive DNA at the end of a eukaryotic chromosome’s DNA molecule; protect the organism’s genes from being eroded during successive rounds of replication

Question 23

chromatin

Answer 23

complex of DNA and proteins that makes up eukaryotic chromosomes; when the cell is not dividing, exists in its dispersed form, as a mass of very long, thin fibers

Question 24

euchromatin

Answer 24

the less condensed form of eukaryotic chromatin that is available for transcription

Question 25

heterochromatin

Answer 25

eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed