Chapter 5

Question 1

Base Pair

Answer 1

Two complementary nucleotides in an RNA or a DNA molecule that are held together by hydrogen bonds— for example, G with C, and A with T or U.

Question 2

Cell Cycle

Answer 2

The orderly sequence of events by which a cell duplicates its contents and divides into two

Question 3

Centromere

Answer 3

Specialized DNA sequence that allows duplicated chromosomes to be separated during M phase; can be seen as the constricted region of a mitotic chromosome.

Question 4

Chromatin

Answer 4

Complex of DNA and proteins that makes up the chromosomes in a eukaryotic cell.

Question 5

chromatin-remodeling complex

Answer 5

Enzyme (typically multisubunit) that uses the energy of ATP hydrolysis to alter the arrangement of nucleosomes in eukaryotic chromosomes, changing the accessibility of the underlying DNA to other proteins, including those involved in transcription.

Question 6

chromosome

Answer 6

Long, threadlike structure composed of DNA and proteins that carries the genetic information of an organism; becomes visible as a distinct entity when a plant or animal cell prepares to divide.

Question 7

complementary

Answer 7

Describes two molecular surfaces that fit together closely and form noncovalent bonds with each other. Examples include complementary base pairs, such as A and T, and the two complementary strands of a DNA molecule.

Question 8

deoxyribonucleic acid

Answer 8

Double-stranded polynucleotide
two separate chains of covalently linked deoxyribonucleotide units. It serves as the cell’s store of genetic information that is transmitted from generation to generation.

Question 9

double helix

Answer 9

The typical structure of a DNA molecule in which the two complementary polynucleotide strands are wound around each other with base-pairing between the strands.

Question 10

euchromatin

Answer 10

One of the two main states in which chromatin exists within an interphase cell. Prevalent in gene- rich areas, its less compact structure allows access for proteins involved in transcription. (See also heterochromatin.)

Question 11

gene

Answer 11

Unit of heredity containing the instructions that dictate the characteristics or phenotype of an organism; in molecular terms, a segment of DNA that directs the production of a protein or functional RNA molecule.

Question 12

gene expression

Answer 12

The process by which a gene makes a product that is useful to the cell or organism by directing the synthesis of a protein or an RNA molecule with a characteristic activity.

Question 13

genetic code

Answer 13

Set of rules by which the information contained in the nucleotide sequence of a gene and its corresponding RNA molecule is translated into the amino acid sequence in a protein.

Question 14

genome

Answer 14

The total genetic information carried by all the chromosomes of a cell or organism.

Question 15

heterochromatin

Answer 15

Highly condensed region of an interphase chromosome; generally gene-poor and transcriptionally inactive. (See also euchromatin.)

Question 16

histone

Answer 16

One of a group of abundant highly conserved proteins around which DNA wraps to form nucleosomes, structures that represent the most fundamental level of chromatin packing.

Question 17

karyotype

Answer 17

An ordered display of the full set of chromosomes of a cell arranged with respect to size, shape, and number.

Question 18

nucleolus

Answer 18

Large structure within the nucleus where ribosomal RNA is transcribed and ribosomal subunits are assembled.

Question 19

replication origin

Answer 19

Nucleotide sequence at which DNA replication is

initiated.

Question 20

telomere gene

Answer 20

Repetitive nucleotide sequence that caps the ends of linear chromosomes. Counteracts the tendency of the chromosome otherwise to shorten with each round of replication.