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Medical Cell Biology and Genetics > Topic 14: DNA and Chromosomal Mutations > Flashcards

Topic 14: DNA and Chromosomal Mutations Flashcards

1
Q

What is the definition of mutation?

A

Change in the nucleotide sequence in DNA

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2
Q

What is the definition of mutagenesis?

A

Process of mutation generation

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3
Q

What are 2 types of single nucleotide changes?

A
  1. Transition

2. Transversion

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4
Q

What is transition?

A

Change to same type of base

purine to purine - A/G
pyrimidine to pyrimidine - C/T

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5
Q

What is transversion?

A

Change to different types of base

Purine (A/G) to pyrimidine (C/T)

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6
Q

What are 4 possible consequences of single nucleotide changes?

A

Change gene product (polypeptide or RNA)
Change amount of gene product
Change polypeptide length
No effect

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7
Q

What is missense mutation?

A

Single nucleotide change resulting in change of amino acid

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8
Q

What is an example of a missense mutation?

A

Sickle cell disease

Mutation in codon 7 of HBB: GAG>GTG = Glu>Val

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9
Q

What is a neutral or silent mutation?

A

Single nucleotide change resulting in no phenotypic change

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10
Q

What is an example of a silent mutation?

A

Mutation in codon 7 of HBB

GAG>GAA = Glu>Glu

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11
Q

What is synonymous mutation?

A

Single nucleotide change results in no effect as it codes for same amino acid

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12
Q

What is non synonymous mutation?

A

Single nucleotide change that results in change in amino acid

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13
Q

What is frameshift mutation?

A

Deletion or insertion leads to change in reading frame

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14
Q

What is mutation of stop codon?

A

Single nucleotide change in stop codon making it another amino acid

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15
Q

What is the result of frame shift mutations or mutations of the stop codon?

A

Change in polypeptide length

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16
Q

What is nonsense mutation?

A

Single nucleotide change leading to creation of stop codon

17
Q

What is the result of nonsense mutation?

A

Change in polypeptide length

18
Q

What is the effect of mutations affecting regulatory sequences?

A

Amount of gene product

19
Q

What is the effect of multi nucleotide deletion/insertion?

A

Deletion/insertion of nucleotides other than multiples of 3bp lead to frame shifts

20
Q

How does fork slippage cause mutations?

A

Fork slippage can lead to backward slippage causing trinucleotide expansions

21
Q

What is an example of trinucleotide repeat disorders?

A

CAG repeats in HTT gene leads to polyglutamine repeats in Huntington protein

> 35 repeats = disease

22
Q

What are transposable elements?

A

Specific repetitive DNA sequences that move

23
Q

How do transposable elements cause mutations?

A
  1. No effect
  2. Inactivate - disrupt gene sequence
  3. Reactivate - move out after disruption
  4. Alter gene expression
24
Q

What are 2 types of chromosomal abnormalities?

A

Numerical and structural

25
Q

What are 3 types of numerical abnormalities in chromosomes?

A

Polyploidy
Aneuploidy
Mosaicism

26
Q

What is polyploidy?

A

Gaining haploid set of chromosomes = triploidy 69 chromosomes

Eg polyspermy when 2 sperms fertilize one egg

27
Q

What is aneuploidy?

A

Loss or gain of whole chromosomes causing trisomies and mono somites

28
Q

What is aneuploidy caused by?

A

Meiotic non disjunction

29
Q

What are 4 examples of trisomies?

A 
Down syndrome (21) 
Patau syndrome (13) 
Edwards syndrome (18) 
Klinefelter syndrome (XXY)
30
Q

What is an example of a monosomy?

A

Turner syndrome (X)

31
Q

What is mosaicism?

A

Presence of 2 or more cell lines in an individual throughout the body or tissue specific

32
Q

What is mosaicism caused by?

A

Mitotic non disjunction

33
Q

What are 5 structural abnormalities of chromosomes?

A 
Deletion 
Duplication
Inversion 
Substitution 
Translocation 
Isochromosomes
Ring chromosomes 
Marker chromosomes
34
Q

What is reciprocal translocation?

A

Part of a chromosome changed places with part of another chromosome

35
Q

What is the meiotic consequence of reciprocal translocation?

A

Quadrivalent forms - 6 possible outcomes leading to 2 balanced and 4 unbalanced gametes

36
Q

What is Robertsonian translocation?

A

2 acrocentric chromosomes fuse, leading to no p arms, only q arm, total only 45 chromosomes

37
Q

What is the meiotic consequence of Robertsonian translocation?

A

Trivalent will form, segregation has 6 outcomes, risk of trisomy is 2/6 monosomy is 2/6, normal 1/6 and balanced carrier is 1/6

38
Q

What is cytogenetic analysis?

A

Study of chromosomes and their structure

39
Q

What are the 4 reasons why we do cytogenetic testing?

A

Accurate diagnosis and prognosis of clinical problems
Better clinical management
Assess future reproductive risks
Prenatal diagnosis

Medical Cell Biology and Genetics (14 decks)

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