Chapter 16 - The Molecular Basis of Inheritance

Question 1

DNA replication

Answer 1

The process by which a DNA molecule is copied; also called DNA synthesis.

Question 2

transformation

Answer 2

(1) The conversion of a normal animal [or human] cell to a cancerous cell. (2) A change in genotype and phenotype due to the assimilation of external DNA by a cell. When the external DNA is from a member of a different species, transformation results in horizontal gene transfer.

Question 3

bacteriophage

Answer 3

A virus that infects bacteria; also called a phage.

Question 4

virus

Answer 4

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

Question 5

double helix

Answer 5

The form of native DNA, referring to its two adjacent antiparallel polynucleotide strands wound around an imaginary axis into a spiral shape.

Question 6

antiparallel

Answer 6

Referring to the arrangement of the sugar-phosphate backbones in a DNA double helix (they run in opposite 5’ → 3’ directions).

Question 7

semiconservative model

Answer 7

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 8

origin of replication

Answer 8

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

Question 9

replication fork

Answer 9

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

Question 10

helicase

Answer 10

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

Question 11

single-strand binding protein

Answer 11

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

Question 12

topoisomerase

Answer 12

A protein that breaks, swivels, and rejoins DNA strands. During DNA replication, topoisomerase helps to relieve strain in the double helix ahead of the replication fork.

Question 13

primer

Answer 13

A short stretch of RNA with a free 3’ end, bound by complementary base pairing to the template strand and elongated with DNA nucleotides during DNA replication.

Question 14

primase

Answer 14

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

Question 15

DNA polymerase

Answer 15

An enzyme that catalyzes the elongation of new DNA (for example, at a replication fork) by the addition of nucleotides to the 3’ end of an existing chain. There are several different DNA polymerases; DNA polymerase III and DNA polymerase I play major roles in DNA replication in <em>E. coli</em>.

Question 16

leading strand

Answer 16

The new complementary DNA strand synthesized continuously along the template strand toward the replication fork in the mandatory 5’ → 3’ direction.

Question 17

lagging strand

Answer 17

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

Question 18

Okazaki fragment

Answer 18

A short segment of DNA synthesized away form the replication fork

Question 19

DNA ligase

Answer 19

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

Question 20

mismatch repair

Answer 20

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

Question 21

nuclease

Answer 21

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 22

nucleotide excision repair

Answer 22

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

Question 23

telomere

Answer 23

The tandemly repetitive DNA at the end of a eukaryotic chromosome’s DNA molecule. Telomeres protect the organism’s genes from being eroded during successive rounds of replication. <em>See also</em>

Question 24

telomerase

Answer 24

An enzyme that catalyzes the lengthening of telomeres in eukaryotic germ cells.