Chapter 6- DNA replication and repair

Question 1

cancer

Answer 1

Disease caused by abnormal and uncontrolled cell proliferation, followed by invasion and colonisation of body sites normally reserved for other cells.

Question 2

DNA ligase

Answer 2

Enzyme that seals nicks that arise in the backbone of a DNA molecule; in the laboratory, can be used to join together two DNA fragments.

Question 3

DNA polymerase

Answer 3

Enzyme that catalyses the synthesis of a DNA molecule from a DNA template using deoxyribonucleoside triphosphate precursors.

Question 4

DNA repair

Answer 4

Collective term for the enzymatic processes that correct damage to DNA.

Question 5

DNA replication

Answer 5

The process by which a copy of a DNA molecule is made.

Question 6

homologous recombination

Answer 6

Mechanism by which double-strand breaks in a DNA molecule can be repaired flawlessly; uses an undamaged, duplicated, or homologous chromosome to guide the repair. During meiosis, the mechanism results in an exchange of genetic information between the maternal and paternal homologs.

Question 7

lagging strand

Answer 7

At a replication fork, the DNA strand that is made discontinuously in short fragments that are later joined together to form one continuous new strand.

Question 8

leading strand

Answer 8

At a replication fork, the DNA strand that is made by continuous synthesis in the 5′-to-3′ direction.

Question 9

mismatch repair

Answer 9

Mechanism for recognising and correcting incorrectly paired nucleotides—those that are non-complementary.

Question 10

mutation

Answer 10

A randomly produced, permanent change in the nucleotide sequence of DNA.

Question 11

nonhomologous end joining

Answer 11

An error-prone mechanism for repairing double-strand breaks in DNA by rejoining the two broken ends; often results in a loss of information at the site of repair.

Question 12

Okazaki fragment

Answer 12

Short length of DNA, including an RNA primer, produced on the lagging strand during DNA replication. Following primer removal, adjacent fragments are rapidly joined together by DNA ligase to form a continuous DNA strand.

Question 13

primase

Answer 13

An RNA polymerase that uses DNA as a template to produce an RNA fragment that serves as a primer for DNA synthesis.

Question 14

proofreading

Answer 14

The process by which DNA polymerase corrects its own errors as it moves along DNA.

Question 15

replication fork

Answer 15

Y-shaped junction at the site where DNA is being replicated.

Question 16

replication origin

Answer 16

Nucleotide sequence at which DNA replication is initiated.

Question 17

ribonucleic acid (RNA)

Answer 17

Molecule produced by the transcription of DNA; usually single-stranded, it is a polynucleotide composed of covalently linked ribonucleotide subunits. Serves a variety of informational, structural, catalytic, and regulatory functions in cells.

Question 18

telomerase

Answer 18

Enzyme that elongates telomeres, synthesizing the repetitive nucleotide sequences found at the ends of eukaryotic chromosomes.

Question 19

telomere

Answer 19

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

Question 20

template

Answer 20

A molecular structure that serves as a pattern for the production of other molecules. For example, one strand of DNA directs the synthesis of the complementary DNA strand.