Chapter 5- DNA and chromosomes

Question 1

base pair

Answer 1

2 complementary nucleotides in an RNA or DNA molecule that are held together by hydrogen bonds- normally G+C and A+T/U

Question 2

cell cycle

Answer 2

the orderly sequence of events by which a cell duplications its contents and divides into 2.

Question 3

centromere

Answer 3

specialised DNA sequence that allows duplicated chromosomes to be separated during M phase (mitosis 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-remodelling complex

Answer 5

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 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 6

complementary

Answer 6

describes 2 molecular surfaces that fit together closely and form non-covalent bonds with each other. Examples include complementary base pairs, e.g. A,T, and the 2 complementary strands of a DNA molecule

Question 7

deoxyribonucleic acid (DNA)

Answer 7

double-stranded polynucleotide formed from 2 separate chains of covalently linked deoxyribonucleotide units. Serves as the cells’ store of genetic information that is transmitted from generation to generation

Question 8

double helix

Answer 8

the typical structure of a DNA molecule in which the 2 complementary polynucleotide strands are wound around each other with base-pairing in between the strands

Question 9

euchromatin

Answer 9

one of the 2 main states in which chromatin exists within an interphase cell. Prevalent in gene-rich ares, its less compact structure allows access for proteins involved in transcription

Question 10

gene

Answer 10

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 11

gene expression

Answer 11

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 specific activity

Question 12

genetic code

Answer 12

a 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 13

genome

Answer 13

the total genetic information carried by al the chromosomes of a cell or organism; in humans, the total number of nucleotide pairs in 22 autosomes plus the X/Y chromosomes

Question 14

heterochromatin

Answer 14

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

Question 15

histone

Answer 15

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

Question 16

histone-modifying enzyme

Answer 16

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 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

nucleosome

Answer 19

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 linker DNA that ties the core particles together.

Question 20

replication origin

Answer 20

Nucleotide sequence at which DNA replication is initiated.

Question 21

telomere

Answer 21

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