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BIOM2202 > Genes and Mutation > Flashcards

Genes and Mutation Flashcards

Module 1

1
Q

The 5’ end possess a(n)…

A

Nucleic acid

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2
Q

The 3’ end has a(n)…

A

Acceptor stem and a contently bound protein

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3
Q

tRNA is an effective intermediate between:

A

mRNA and ribosomes

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4
Q

Each type of tRNA has ONE specific amino acid that can be added. This holds true for all aa excluding:

A

Methionine and tryptophan

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5
Q

tRNAs require 2 levels of specificity:

A
  1. Recognise correct protein

2. Recognise correct place within sequence

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6
Q

The anticodon is read…

A

3’ - 5’

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7
Q

Abnormal bases are created via

A

Post-transcriptional modification

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8
Q

Abnormal tRNAs allow for:

A

Greater flexibility than with A, U, C, or G

i.e. Introducing Inosine

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9
Q

Inosine forms hydrogen bonds with:

A

A, U, and C

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10
Q

“H” is reffered to as….

A

Not “G”

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11
Q

Inosine is created by the…

A

Deamination of adenine into hypoxanthine

Gives altered binding specificity

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12
Q

Inosine is exclusive to anti-codons. T/F

A

False

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13
Q

Conservation of tRNA initiates…

A

Conservation of ribosomes

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14
Q

The triplet code was discovered by:

A

Niernberg and Matthaei

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15
Q

Niernberg and Matthaei

discovered that protein synthesis requires:

A
  1. Amino acids
  2. tRNA
  3. Ribosomes
  4. ATP
  5. GTP
  6. mRNA template
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16
Q

Poly(U) codes for:

A

Phenylalanine

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17
Q

Poly(A) codes for:

A

Polylysine

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18
Q

Poly(C) codes for

A

Polyproline

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19
Q

What happened if the tRNA was mutated, such that some was poking out?

A
  1. tRNA molecule would get stuck in aminoacyl site
  2. Ribosome is now ineffective; can no longer create protein
  3. Every ribosome would get stuck on every bad tRNA molecule produced
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20
Q

DNA must be stable (as oppose to RNA) because it…

A

Needs to maintain intact across generations

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21
Q

RNA must be unstable for…

A

Template and synthesis control

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22
Q

A doublet code signals:

A

2 nucleotides per amino acid

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23
Q

Poly(G) results in:

A

Base-pairing between guanine residues result in 3-stranded structures that cannot be used

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24
Q

Methionine exclusively signals the start of synthesis. T/F

A

False. Methionine has 2 tRNAs.

One for START(AUG) and one for AUG within a sequence

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25
Q

The 3 stop codons:

A

UAA, UAG, UGA

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26
Q

Most degradency is in the x position:

A

3rd

  • -> Valine –> GTT, GTC, GTA, GTG
  • Regardless of 3rd pos. GTx will always code for valine
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27
Q

DNA is almost universal-

Describe an exception:

A

CUG encodes serine instead of leucine in some Candida species –> Candida albicans (mutation withtin tRNA CUG –> CTG)

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28
Q

How many tRNA genes does an organism need to survive?

A

32
Every amino acid must have its own tRNA gene
–> The wobble hypothesis

The last base in the anticodon (pos.1) can wobble
Extra base-pair options compared to standard A = U & G = C

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29
Q

Standard Watson-Crick base pairing is strictly for x:

A

The first 2 bases

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30
Q

How do tRNAs interact with codons?

A
  1. Standard Watson-Crick base pairing (GC, AT)
  2. Rules of wobble base pairing, and how it applies in anticodon position 1 (and ONLY in anticodon position 1)
  3. That each codon/anticodon interaction must follow the rules of the genetic code
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31
Q

The presence of UUI will…

A

Poison the cell

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32
Q

DNA has __ rf while mRNA has __ rfs

A

DNA has 6 reading frames and mRNA has 3 reading frames

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33
Q

Open Reading Frame (ORF):

A

A region in any reading frame that begins with a start codon (ATG) and ends with a stop codon

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34
Q

Disulfide bonds are composed of:

A

Cystine residues

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35
Q

Mutation is inevitable:

A
  • Spontaneous deamination of cytosine (conversion to uracil)
    –> Mistakes then occur during replication and repair
    Spontaneous hydrolysis of purines (guanine & adenine)
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36
Q

Environmental stress causes mutations. T/F

A

False

–> selects for mutants that are best adapted to the environmental stress

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37
Q

Forward mutation:

A

wT –> mutant

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38
Q

Reverse mutation:

A

Second mutation that restores original phenotype

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39
Q

Back mutation:

A

Second mutation at the same site

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40
Q

Suppressor mutation:

A

Second mutation at a different location

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41
Q

Isoalleles:

A

No effect on phenotype; small effects can only be recognised with certain techniques

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42
Q

Null alleles:

A

No gene product; or non-functional gene products

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43
Q

Neutral mutations:

A

No effect on phenotype (–> Isoallele)

44
Q

Recessive lethal mutations:

A

Lethal in homozygous only

45
Q

Conditional lethal mutations:

A

Lethal in restrictive condition

Viable in permissive condition

46
Q

Auxotrophs:

A

Unable to synthesise an essential metabolite that is synthesised by prototrophs

47
Q

Suppressor-sensitive mutants:

A

Viable when a second genetic factor i.e. Suppressor is present ONLY

48
Q

Silent mutation:

A

Does not change the gene product expressed by an organism

49
Q

Synonymous mutation:

A

New codon, no amino acid change

50
Q

Non-synonymous mutations consist of:

A

Conservative substitution and Non-conservative mutations

51
Q

Conservative substitution:

A

a new amino acid that has similar properties to the one it replaced

52
Q

Non-conservative substitution:

A

A new amino acid that has different properties to the one it replaced

53
Q

Neutral mutation:

A

Amino acid substitution causes no change in biological function

54
Q

Missense mutation:

A

Amino acid substitution leads to the protein being defective

55
Q

Nonsense mutation:

A

Premature STOP codon –> loss of function

56
Q

Synonymous mutations are often silent. T/F

A

True –> no amino acid change

57
Q

Tautomeric shift:

A

The spontaneous isomerization of a nitrogen base to an alternative hydrogen-bonding form, possibly resulting in a mutation
i.e. Transitions and transversions

58
Q

Mutagenesis via Ultraviolet Radiation

A
  1. Hydrolysis of cytosine may cause mispairing during replication
  2. Cross-linking of adjacent thymine forms thymine dimers
  3. Tymine dimers block DNA replication
  4. activate error-prone DNA repair mechanism
59
Q

Insertions and Deletions (Indels)

A
  • Cause frameshift mutations within open reading frames
60
Q

Afltoxin produces:

A

frame-shift mutations

Often encode non-sense mutations

61
Q

Ionising radiation:

A

Breaks chromosomes and can causes deletions, duplications, inversions and translocations
- i.e. Hydroxylamine hydroxylates cytosine and initiates G:C and A:T transitions

62
Q

Alkylating agents:

A

Chemicals that donate alkyl groups to other molecules; transitions, transversions, frameshifts, and chromosomal aberrations.

63
Q

Intragenic Suppressor mutations:

A

a second mutation within the same gene but different codon

64
Q

Suppressor mutations:

A

when a second mutation overcomes the deleterious effects(s) of the first mutation. Mutations that mask the present of the first

65
Q

Amber mutations:

A

Suppress UAG termination sequence

66
Q

The Ames Test:

A

Screening chemicals for mutagenicity

- Mutagens will cause reversions, producing histidine prototrophs

67
Q

In eukaryotes, crossing over is associated with:

A

The formation of the synaptonemal complex during prophase of meiosis 1

68
Q

Crossing over involves:

A
  1. The breakage of parental chromosomes
  2. Re-joining the parts in new combinations

*The Holliday model is one of the most widely supported explanations of the molecular basis of recombination

69
Q

Garrod proposed:

A

One gene - One metabolic block

70
Q

One gene - One metabolic block

A

Inborn errors of metabolism; discovered The first recessive allele in humans

- Mutations in homogentisic acid oxidase leads to the production of black urine, kidney stones, cartilage damage and heart disease
- Mutations in phenylalanine hydroxylase cause mental impairment, light hair colour, and the presence of metabolites in blood and urine
71
Q

Beadle and Tatum proposed:

A

One gene, One enzyme

72
Q

One gene, One enzyme:

A

Proposed that biosynthesis of essential metabolites is under genetic control

- Mutations in genes involved in biosynthesis of metabolites would produce strains with additional growth factor requirements
- One mutation resulted in the loss of one enzyme activity
73
Q

The Complementation Test:

A

Provides an operational definition of the gene when used with recessive mutations

74
Q

Amino acids differ from one-another by:

A

R-group

75
Q

The correct anticodon sequence for “AUG” is:

A

UAC

76
Q

What is found in tRNA but not mRNA?

A

Inosine

77
Q

Most amino acids are specified by 2-4 codons. This means that the genetic code is:

A

Degenerate

78
Q

With a few exceptions, all 64 codons have the same meaning in all organisms. This means that the genetic code is:

A

Universal

79
Q

What type of bind occurs between the nucleotide bases in the codon and anticodon?

A

Hydrogen

80
Q

Which position in the anticodon is the wobble position?

A

5’ end

81
Q

If a mutation occurs in a somatic cell, the resulting mutant phenotype will occur:

A

In both the progeny of that individual cell and the individual cell itself

82
Q

Mutation is a random, non-adaptive process. This was first proven by:

A

Joshua and Esther Lederberg, using replica-plated e.coli and streptomyocin as an environmental stress

83
Q

A gene “x” undergoes a mutation which converts it from a wT to mutant. A second mutation occurs at the same site which causes the wT phenotype of gene “x” to be restored. What are the mutations that occurred?

A

Forward mutation

Suppressor mutation

84
Q

Muller found that:

A

X-rays can result in gross changed of chromosomal structure, such as large deletions, duplications, and inversions.

85
Q

Bruce Ames constructed a mutagenicity test which initially missed carcinogens that were non-carcinogenic to the tester strains. What did Ames fail to realise?

A

Potential carcinogens needed to be modified in eukaryotes before they were mutagenic

86
Q

Light-dependant repair corrects:

A

Thymine dimers

87
Q

Nucleotide excision repair:

A

Removes large regions of DNA via an exinuclease which cuts on either side of the damaged bases

88
Q

Error-prone repair is:

A

Template-independant and requires polymerase activity

89
Q

Light dependant repair requires:

A

DNA photolyase

90
Q

Cf is a disease associated with a defect in DNA repair. T/F

A

False

91
Q

RecA is critical in the process of…

A

Recombination

92
Q

Gene conersion of Neurospora requires combination of:

A

Heteroduplex formation

93
Q

Wilhelm Johannsen:

A

Introduced a ‘gene’ in 1909

94
Q

Beadle and Tatums concept has further been refined to:

A

One gene - One transcript

95
Q

Beadle and Tatum used ___ to support their one gene - one enzyme concept:

A

Neurospora

96
Q

In 1940, Clarence P published first evidence indicating that recombination could occur using…

A

Drosophila

97
Q

The nucleotide-pair sequences of coding regions and amino acid sequences are considered to be:

A

Colinear

Est. Charles Yanofsky

98
Q

When 2 mutations are on the same chromosome, the arrangement is:

A

Coupling configuration and Cis configuration

99
Q

When 2 mutations are on different chromosomes, the arrangement is:

A

Trans configuration an Repulsion configuration

100
Q

Within a trans test, dominant mutations would lead to

A

Invalid results

101
Q

When mutations exhibit complementation, the mutations are located:

A

In different genes

102
Q

The control for a complementation test is the:

A

Cis test

103
Q

When a protein is a multimet containing >2 copies of one gene product ___ may occur.

A

Intragenic complementation

104
Q

Complementation analysis used by Benzer in his rll anaysis:

A

determined whether 2 mutations fall int he same gene

105
Q

Garrod found that mutations in homogentisic acid oxidase leads to…

A

the production of black urine, kidney stones, cartilage damage and heart disease

106
Q

Garrod found that mutations in phenylalanine hydroxylase cause

A

mental impairment, light hair colour, and the presence of metabolites in blood and urine

BIOM2202 (5 decks)

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