Chapter 16: The Molecular Basis of Inheritance

Question 1

antiparallel

Answer 1

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

Question 2

bacteriophages

Answer 2

A virus that infects bacteria; also called a phage

Question 3

chromatin

Answer 3

The complex of DNA and proteins that makes up eukaryotic chromosomes. When the cell is not dividing, chromatin exists in its dispersed form, as a mass of very long, thin fibers that are not visible with a light microscope.

Question 4

double helix

Answer 4

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

Question 5

euchromatin

Answer 5

The less condensed form of eukaryotic chromatin that is available for transcription.

Question 6

helicase

Answer 6

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

Question 7

heterochromatin

Answer 7

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

Question 8

lagging strand

Answer 8

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 9

leading strand

Answer 9

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

Question 10

mismatch repair

Answer 10

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

Question 11

nucleoid

Answer 11

A non-membrane-bounded region in a prokaryotic cell where the DNA is concentrated.

Question 12

origin of replication

Answer 12

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

Question 13

phage

Answer 13

A virus that infects bacteria; also called a bacteriophage.

Question 14

replication fork

Answer 14

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

Question 15

semiconservative model

Answer 15

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 16

single-strand binding protein

Answer 16

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 17

transformation

Answer 17

(1) The conversion of a normal animal 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 18

virus

Answer 18

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.