Exam 2 (Ch.15- Mutations)

Question 1

a heritable change in the genetic material & provide allelic variations

Answer 1

Mutation

Question 2

3 types of mutations

Answer 2

1. chromosome mutations
2. genome mutations
3. single-gene mutations

Question 3

mutations in the DNA resulting from an agent: UV, radiation, chemicals

Answer 3

induced mutations

Question 4

random change in the DNA due to errors in replication that occur without known cause

Answer 4

spontaneous mutations

Question 5

• Changes in chromosome structure
• Ex: huge deletions of chromosomes

Answer 5

Chromosome mutations

Question 6

• Changes in chromosome number
• Ex: Trisomy 21

Answer 6

Genome Mutations

Question 7

• Relatively small changes in DNA structure that occur within a particular gene

Answer 7

single gene mutations

Question 8

gene mutation in which a single base pair in DNA has been changed/ base substitution

Answer 8

point mutation

Question 9

type of point mutation:

a change of a pyrimidine (C, T) to another pyrimidine or a purine (A, G) to another purine

Answer 9

Transition (most common)

Question 10

type of point mutation:

a change of a pyrimidine to a purine or vice versa

Answer 10

Transversion

Question 11

A mutation involving the addition of one or more nucleotide pairs to a gene. (detrimental when occurs closer to the 5’ end)

Answer 11

Insertion/Addition

Question 12

A change to a chromosome in which a fragment of the chromosome is removed.

Answer 12

Deletion

Question 13

A mutation that changes a single nucleotide, but does not change the amino acid created. due to degeneracy

Answer 13

silent mutation

Question 14

A base-pair substitution that results in a codon that codes for a different amino acid.

Answer 14

missense mutation

Question 15

A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.

Answer 15

nonsense mutation

Question 16

involve the addition or deletion of nucleotides in multiples of one or two

Answer 16

frameshift mutation

(This shifts the reading frame so that a completely different amino acid sequence occurs downstream from the mutation)

Question 17

mutation that causes base substitutions in which one base pair is altered

Answer 17

point mutations

Question 18

mutation that results from insertions or deletions of a base pair

Answer 18

frameshift mutations

Question 19

Changes the wild-type genotype into some new variation (the mutant allele)

Answer 19

forward mutation

Question 20

changes a mutant phenotype back to the wild-type phenotype

Answer 20

reverse mutation (aka reversion)

Question 21

When a mutation alters an organism’s phenotypic characteristics

Answer 21

variant

Question 22

Genetic changes that are harmful to an organism and decreases fitness

Answer 22

deleterious mutation

Question 23

a gene or chromosomal mutation that influences the development of an organism in such a way that the organism cannot survive

Answer 23

lethal mutation

Question 24

any change to the genetic code that results in noticeable physiological changes that are of benefit to the organism

Answer 24

Beneficial Mutation

Question 25

a mutant whose phenotype depends on the environmental conditions, such as a temperature-sensitive mutant (most common)

Answer 25

conditional mutants

Question 26

upstream 5' end before the open reading frame/specific region of a gene where RNA polymerase can bind and begin transcription. --> a mutation may alter the sequence

Answer 26

Promoter

Question 27

make the promoter more like the consensus sequence - may increase the rate of transcription

Answer 27

up promoter mutation

Question 28

mutations make the promoter less like the consensus sequence - may decrease the rate of transcription

Answer 28

down promoter mutation

Question 29

may alter the ability of pre-mRNA to be properly spliced (introns get spliced)

Answer 29

splice recognition sequence

Question 30

A large complex made up of proteins and RNA molecules that splices RNA by interacting with the ends of an RNA intron, releasing the intron and joining the two adjacent exons.

Answer 30

spliceosome

Question 31

produce neither adverse or helpful changes =, in humans the vast majority of all mutations occur in the large portions of the genome that do not contain genes and therefore have no effect on gene products

Answer 31

neutral mutations

Question 32

no gene function (no gene product or non-functional product) - usually recessive but can be dominant

Answer 32

null mutation

Question 33

- reduced gene function ( protein retains part of its activity) - usually recessive but can be dominant

Answer 33

hypomorphic mutation

Question 34

phenotype depends on how protein function is changed by a mutation: - enhanced gene function (protein functions more efficiently) - extremly rare - usually dominant

Answer 34

hypermorphic mutation

Question 35

novel gene function (proteins has novel properties or is expressed ectopically, at the wrong place or the wrong time) - dominant

Answer 35

neomorphic mutation

Question 36

loss of function mutation

Answer 36

null, hypomorphic

Question 37

gain of function mutation

Answer 37

hypermorphic, neomorphic

Question 38

Results from abnormalities in cellular/biological processes - errors in DNA replication - underlying cause originates within the cell

Answer 38

spontaneous mutations

Question 39

- Caused by environmental agents - Agents that alter DNA structure are called mutagens

Answer 39

induced mutations

Question 40

What is the range of frequency of mutation? ____ ___ in every 10^4 to 10^8 ___

Answer 40

1 mutation; gametes

Question 41

test demonstrated that mutations are not adaptive but occur spontaneous

Answer 41

Luria-Delbruck fluctuation

Question 42

- studied the resistance of E. coli to bacteriophage T1 - discovered fluctuation in number of colonies that gained resistance to T1 - showed a non-linearization of mutation (spontaneous) - ton^r (T One Resistance)

Answer 42

Luria-Delbruck fluctuation

Question 43

the ____ ___ theory predicts that the number of tonr bacteria is essentially constant in different bacterial populations

Answer 43

physiological adaption

Question 44

the ____ ____ theory predicts that the number of tonr bacteria will fluctuate in different bacterial populations - prove this theory was better -conclusion: mutations arise randomly

Answer 44

spontaneous mutation

Question 45

- Depurination (most common) - Deamination - Oxidation - Tautomeric shift

Answer 45

four chemical changes that cause spontaneous mutations

Question 46

- involves the removal of a purine (G or A) from DNA - the covalent bond between deoxyribose and a purine is somewhat unstable - occasionally undergoes a spontaneous reaction with water that releases the base from the sugar -- The site of release is the apurinic site occurs approx. 1000 times an hour

Answer 46

depurination (apurinic sites can be repaired)

Question 47

AP (apurinic) sites -------> ____ (usually replaced by T)

Answer 47

transversions

Question 48

- When Cytosine loses its amino group and becomes Uracil - Estimated to occur 100 times per day in every human cell

Answer 48

deamination

Question 49

Deamination: C --> T ------> ___

Answer 49

transition

Question 50

- DNA may suffer.. damage by the by-products of normal cellular processes - caused by hydrogen peroxide (H2O2), hydroxyl radicals (OH-), superoxide radicals (O2-)

Answer 50

oxidation

Question 51

Oxidation: G --> T --------> ___

Answer 51

Transversion

Question 52

isomers that differ in a single proton shift in the molecule, creating a change in the bonding structure of the molecule

Answer 52

tautomers

Question 53

the keto (standard) --> enol (anomalous) form of

Answer 53

thymine and guanine - tautomers shifts

Question 54

amino (standard) --> imino (anomalous) forms of

Answer 54

cytosine and adenine - tautomers shifts

Question 55

keto and amino tautomers shifts allow hydrogen bonding with ____ ____ - & can result in mutations because of _____ base pairing

Answer 55

noncomplementary bases; anomalous (T to G and C to A)

Question 56

____ mutations arise from DNA damage caused by chemicals or radiation

Answer 56

induced

Question 57

3 types of chemical mutagens

Answer 57

- Base modifiers - Intercalating agents - Base analogues

Question 58

- Mutagens that covalently modify the structure of a nucleotide --- ex: nitrous acid can replace amino groups with keto groups causing deamination - Can change cytosine to uracil and adenine to hypoxanthine

Answer 58

base modifiers

Question 59

chemical mutagens disrupt the appropriate pairing between nucleotides by ___ ____ within the DNA -- ex: nitrogen mustards and ethyl methanesulfonate EMS

Answer 59

Alkylating bases (another way chemical mutagens disrupt the appropriate pairing between nucleotides)

Question 60

- contain flat planar structures that intercalate themselves in the double helix - this distorts the helical structure and increase the rate of single-nucleotide additions/deletions resulting in frameshift

Answer 60

intercalating agents

Question 61

example of intercalating agents

Answer 61

- acridine dyes (cause frameshift mutations by intercalates between purines and pyrimidines) - proflavin

Question 62

- can substitute purines for pyrimidines during nucleic acid replication - become incorporated into daughter strands during DNA replication

Answer 62

base analogs

Question 63

base analogs example: 5-bromouracil is a ___

Answer 63

thymine analogue - it can be incorporated into DNA instead of thymine

Question 64

A test used to asses the mutagenicity of compounds - Uses strains of Salmonella typhimurium for their increase sensitivity to mutations and their ability to reveal the presence of specific types of mutations - has shown many carcinogens to be strong mutagens

Answer 64

Ames test

Question 65

What are the two types of physical mutagens?

Answer 65

- Ionizing radiation - non-ionizing radiation

Question 66

- X-rays and gamma rays - has short wavelengths and high energy - can penetrate deep into biological molecules - can cause double-strand breaks and deletions/inversions

Answer 66

ionizing radiation

Question 67

- includes UV light - has less energy - cannot penetrate deeply into biological molecules - causes the formation of cross-linked pyrimidine dimers - thymine dimers may cause mutations when DNA is replicated

Answer 67

nonionizing radiation

Question 68

- prior to DNA replication - Corrects the DNA damage caused by UV-induced pyrimidine dimers

Answer 68

nucleotide excision repair (NER)

Question 69

- prior to DNA replication - corrects damage from oxidation, deamination and alkylation of DNA bases. these bases lesions can be spontaneous or induced

Answer 69

base excision repair (BER)

Question 70

mainly post-DNA replication - errors after proofreading by the DNA polymerase can be fixed by this mechanism

Answer 70

Mismatch repair (MMR)

Question 71

proofreading by DNA polymerase: occurs __

Answer 71

- during DNA replication

Question 72

Deamination of cytosine can be repaired by ____

Answer 72

base-excision repair

Question 73

involves: - recognition of the erroneous base by DNA glycosylase - cutting of DNA backbone by AP endonuclease

Answer 73

base excision repair (BER)

Question 74

frequency of tautomeric forms predicts 1 transition in ____ base pairs

Answer 74

10.000

Question 75

- Base excision repair (BER) - Nucleotide excision repair (NER) - Proofreading function of DNA polymerase - Mismatch repair (MMR)

Answer 75

repair mechanisms

Question 76

1. Removal of the mutation & additional bases by a nuclease 2. gap-filling by DNA polymerase 3. sealing of the nick by DNA ligase

Answer 76

3 steps of mismatch excision repair