Ch 5 - DNA and Chromosomes

Question 1

base pair

Answer 1

two complementary nucleotides in an RNA or a DNA molecule that are held together by hydrogen bonds - normally G with C or A with T / 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-remodeling complex

Answer 4

enzyme (typically multi-subunit) 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

Question 5

chromatin

Answer 5

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

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 (DNA)

Answer 8

double-stranded polynucleotide formed from 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-paring 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 particular 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 of a protein

Question 14

genome

Answer 14

the total genetic information carried by all the chromosomes of a cell or organism; in humans, the total number of nucleotide pairs in the 22 autosomes plus the x and y chromosomes

Question 15

heterochromatin

Answer 15

highly condensed region of an interphase chromosome; generally gene-poor and transcriptionally inactive

Question 16

histone

Answer 16

one of the small 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

histone-modifying enzyme

Answer 17

enzyme that catalyzes the covalent addition of a small molecule, such as a methyl or acetate group, to a specific amino acid side chain on a histone

Question 18

karyotype

Answer 18

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

Question 19

nucleolus

Answer 19

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

Question 20

nucleosome

Answer 20

beadlike structural unit of a eukaryotic chromosome composed of a short length of DNA wrapped around an octameric core of histone proteins; includes a nucleosomal core particle (DNA plus histone protein) along with a segment of linked DNA that ties the core particles together

Question 21

replication origin

Answer 21

nucleotide origin at which DNA replication is initiated

Question 22

telomere

Answer 22

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