Mutations and Genetic Analysis Flashcards

1
Q

What are the 3 types of chromosomal abnormalities?

A
  • numerical
  • structural
  • mutational
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2
Q

What happens to most foetuses which have chromosomal abnormalities?

A

first trimester miscarriage

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3
Q

What type of chromosomal abnormality accounts for 50% of first trimester miscarriages?

A

Trisomy

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4
Q

Name a monosomy syndrome?

A

Turner syndrome, 45 X

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5
Q

What are 3 trisomy syndromes?

A
  • Patau 47,XX+13
  • Edwards 47,XY+18
  • Down 47,XX+21
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6
Q

What is the chromosome complement of Klinefelter Syndrome?

A

47,XXY

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7
Q

Where do most cases of non-disjunction originate?

A

In the mother

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8
Q

What are the characteristic of Down’s Syndrome?

A
  • characteristic facial dysmorphologies
  • IQ less than 50
  • Average life expectancy 50-60 years
  • Alzheimer’s disease in later life
  • Usually a result of maternal non-disjunction (also unbalanced Robertsonian translocation and Mosaicism)
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9
Q

What are the characteristic of Patau Syndrome?

A
  • multiple dysmorphic features and mental retardation
  • Very few survive beyond first year
  • usually a result of maternal non-disjunction (also unbalanced Robersonian translocation)
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10
Q

What are the characteristics of Edwards Syndrome?

A
  • severe developmental problems; most patients die within first year
  • usually caused by maternal non-disjunction
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11
Q

What are 2 examples of sex chromosome aneuploidy syndromes?

A
  • Turner Syndrome

- Klinefelter Syndrome

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12
Q

What are the characteristics of Turner Syndrome?

A
  • mainly result in miscarriage
  • females of short stature and infertile
  • neck webbing and widely spaced nipples
  • intelligence and lifespan is normal
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13
Q

What are the characteristics of Klinefelter syndrome?

A
  • tall stature, long limbs
  • male but infertile, small tested, about 50% gynaecomastia
  • mild learning difficulties
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14
Q

What does structural abnormalities include?

A
  • balanced or unbalanced rearrangements
  • translocations
  • deletions
  • insertions
  • inversions
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15
Q

What are the 2 kinds of translocation?

A
  • Reciprocal: involving breaks in 2 chromosomes with formation of 2 new derivative chromosomes
  • Robersonian: fusion of two acrocentric chromosomes
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16
Q

What types of mutation are there?

A
  • non-coding

- coding which can be silent, missense, nonsense, frameshift (deletion/insertion)

17
Q

What point mutations exist?

A
  • transitions

- transversions

18
Q

What is a transition mutation?

A
  • A mutation which changes a purine nucleotide to another purine nucleotide A>G
    OR
    A mutation which changes a pyrimidine nucleotide to another pyrimidine nucleotide C>T
19
Q

What is a transversion mutations?

A

A substation of purine for a pyrimidine A>C
OR
A substitution of pyrimidine for a purine C>G

20
Q

How can mutations be detected?

A
  • polymerase chain reaction (PCR)
  • gel electrophoresis
  • restriction fragment length polymorphism (RFLP) analysis
  • amplification refractory mutation system (ARMS)
  • DNA sequencing
21
Q

What is needed for PCR?

A
  • sequence information
  • oglionucleotide
  • DNA
  • nucleotides
  • DNA polymerase
22
Q

What 3 steps are repeated in PCR?

A
  • denature
  • anneal
  • extend
23
Q

Describe gel electrophoresis.

A
  • separate DNA fragments
  • apply an electrical field
  • DNA is negatively charged
  • separate through agarose gel matrix
  • visualise DNA fragments
24
Q

What are the advantages of gel electrophoresis?

A
  • speed
  • ease of use
  • sensitive
  • robust
25
Q

What can PCR be used for?

A
  • DNA cloning
  • DNA sequencing
  • In vitro mutagenesis
  • gene identification
  • gene expression studies
  • forensic medicine
  • typing genetic markers
  • detection of mutations
26
Q

What are the advantages/disadvantages of ARMS?

A
  • Advantages= cheap, labelling not required
  • Disadvantages= electrophoresis required, primer design critical, need sequence information, limited amplification size, limited amounts of product, infidelity of DNA replication
27
Q

What are restriction endonucleases?

A
  • enzymes from bacterial cells that provide a protective mechanism by degrading DNA of invading viruses.
  • they recognise specific DNA sequences, usually 4-8 bp long and always cut DNA at the same site
28
Q

What are the advantages/disadvantages of RFLP?

A
  • advantages= simple, cheap, non-radioactive

- disadvantages= requires gel electrophoresis, not always feasible

29
Q

How can DNA be sequenced?

A
  • chain termination method

- use of dideoxynucleotides

30
Q

What are the advantages/ limitations of DNA sequencing by Sanger?

A
-advantages= mutation detection, automation and high throughput, next generation sequencing
limitations= expensive equipment, poor quality sequence read