Chapter 12

Question 1

DNA mutation

Answer 1

An inheritable change in DNA sequence

Question 2

The change of a single base pair is known as

Answer 2

point mutation

Question 3

where one purine-pyrimidine base pair is exchanged for another purine-pyrimidine pair (C≡G becomes T=A or vice versa)

Answer 3

transition mutation

Question 4

where a purine-pyrimidine base pair is replaced with a pyrimidine-purine base
pair, or vice versa (ex: C≡G becomes either G≡C or A=T).

Answer 4

transversion mutation

Question 5

does not change any amino acid in the protein (due to the redundancy of codons).

Answer 5

silent mutation

Question 6

a point mutation generating a change in a single amino acid. [example: glutamate
(GAA) to glutamine (CAA) exchange]

Answer 6

missense mutation

Question 7

induces instead of an amino acid codon, a stop codon. This generates a truncated
protein.

Answer 7

nonsense mutation

Question 8

Mutations are incorporated in how many steps

Answer 8

two-step process

Question 9

A mutation caused by insertion of one or more extra bases between successive bases in DNA.

Answer 9

insertion mutation

Question 10

A mutation resulting from the deletion of one or more nucleotides from a gene or chromosome. Compare insertion mutation.

Answer 10

deletion mutation

Question 11

A collective term for insertion and deletion mutations

Answer 11

indels

Question 12

A mutation caused by insertion or deletion of one or more paired nucleotides, changing the reading frame of codons during protein synthesis; the polypeptide product has an altered amino acid sequence beginning at the mutated codon.

Answer 12

frameshift mutation

Question 13

The duplication of a large tract of DNA, leading to an increased dosage of genes in the affected area.

Answer 13

duplication mutation

Question 14

A mutation that results from the inversion of a large segment of DNA in a chromosome.

Answer 14

inversion mutation

Question 15

A mutation that results from the exchange of large segments of DNA between nonhomologous chromosomes.

Answer 15

translocation mutation

Question 16

causes of indels

Answer 16

1. abberant recombination
2. template slippage by dna polymerase

Question 17

The enzymatic removal of amino groups from biomolecules such as amino acids or nucleotides

Answer 17

deamination

Question 18

A position in an intact DNA backbone that is missing the base. Also called an AP (apurinic or apyrimidinic) site.

Answer 18

abasic site

Question 19

A mutation in a gene that reverses a previous mutation. Also called a back mutation. A true reversion restores the original gene sequence; a second-site reversion restores the functionality (phenotype)

Answer 19

reversion mutation

Question 20

the addition of an alkyl group to atoms in the
nucleotide bases or to the phosphodiester bond

Answer 20

alkylation

Question 21

A covalently joined dimer of two adjacent pyrimidine residues in DNA, induced by absorption of UV light; most commonly derived from two adjacent thymines

Answer 21

pyrimidine dimer

Question 22

a cross-linking agent. It alkylates DNA at
the N7 position of purines

Answer 22

cisplatin

Question 23

effects of cisplatin

Answer 23

can form either intra-strand or inter-strand cross-links that are hard to repair and usually stop the
replication fork, ultimately leading to cell death.

Question 24

a complex biomolecule isolated from a bacterium.

Answer 24

bleomycin

Question 25

effects of bleomycin

Answer 25

binds an atom of iron and activates molecular oxygen to form hydroxyl radicals that damage DNA. It typically does so by binding to DNA.

Question 26

A structure formed by the condensation of two double-bonded C5=C6 atoms on adjacent pyrimidine bases in DNA.

Answer 26

cyclobutane ring

Question 27

can be used to damage dna such as uv light

Answer 27

ionizing radiation

Question 28

An enzymatic system for repairing base mismatches (non-Watson-Crick pairs) in DNA.

Answer 28

mismatch repair (mmr)

Question 29

An enzyme of E. coli that methylates adenine residues in the palindromic sequence GATC on both strands of the DNA. Transient hemimethylation of a DNA duplex following replication distinguishes the parental strand from the daughter strand.

Answer 29

dam methylase

Question 30

scans the DNA: using ATP it moves bidirectional on the two directions of the strand, forming a DNA loop. The complex scans the DNA until it finds a hemimethylated GATC sequence

Answer 30

MutS-MutL complex

Question 31

which unwinds DNA towards the mismatch

Answer 31

Helicase II

Question 32

The repair of a cyclobutane pyrimidine dimer by electron transfer from a DNA photolyase

Answer 32

photoreactivation

Question 33

A flavoprotein enzyme that becomes an electron donor when activated by visible light. DNA photolyases can repair pyrimidine dimers and other lesions caused by ultraviolet light

Answer 33

dna photolyase

Question 34

A DNA repair pathway that involves excision of a damaged base by DNA glycosylase, followed by cleavage of the DNA backbone adjacent to the site by an AP endonuclease. Nick translation, DNA polymerization, and ligation complete the repair.

Answer 34

Base Excision Repair (BER)

Question 35

An enzyme that hydrolyzes the N-β-glycosyl bond between a nucleotide base and pentose, creating an abasic site in the DNA.

Answer 35

dna glycosylase

Question 36

Enzymes that cleave the DNA backbone at an AP (apurinic or apyrimidinic; abasic) site as part of the base excision repair pathway

Answer 36

ap endonucleases

Question 37

a DNA polymerase synthesizes a new DNA strand by elongating the 3’-OH and by doing so displaces the old 5’-end of the nicked strand.

Answer 37

long patch repair

Question 38

Pol β inserts a single nucleotide and then a ligase completes the work.

Answer 38

short patch repair

Question 39

A DNA repair pathway that involves excinuclease-catalyzed cleavage of the phosphodiester bond on either side of a bulky DNA lesion such as a pyrimidine dimer or base adduct, followed by removal of the segment containing the lesion, then DNA polymerization and ligation to fill the gap

Answer 39

nucleotide excision repair

Question 40

An enzyme that cleaves a phosphodiester bond in the DNA on either side of a bulky lesion in DNA. Also called an excision endonuclease.

Answer 40

excinuclease

Question 41

scans the DNA looking for damage during nucleotide excision repair

Answer 41

UvrA2 -UvrB

Question 42

A nucleotide excision repair pathway in eukaryotes that is triggered when RNA polymerase encounters a lesion in the DNA and stalls.

Answer 42

transcription-coupled repair (TCR)

Question 43

A pathway for replicating DNA across lesions that occur in unwound DNA at the replication fork. The pathway uses a TLS polymerase that lacks a proofreading exonuclease and has a less-selective active site. Although this polymerase may introduce a mutation, it allows replication to proceed.

Answer 43

translesion synthesis (TLS)