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PoD > Chromosome Biology 2 > Flashcards

Chromosome Biology 2 Flashcards

1
Q

What types of chromosomal abnormalities can arise?

A
  • Numerical
  • Structural
  • Mutational
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2
Q

What stages have the highest percentage incidence of abnormalities?

A

First trimester abnormalities - 50%

Children with mental retardation - 35-40%

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3
Q

Name two numerical abnormalities

A
  • Trisomy (extra chromosome)

- Monosomy (loss of chromosome)

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4
Q

Name three trisomy conditions and the abnormality

A
  • Patau: 47,XX+13
  • Edwards: 47,XY+18
  • Down: 47,XX+21
  • Klinefelter: 47,XXY
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5
Q

Name a monosomy condition and the abnormality

A

Turner: 45,X

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6
Q

What does 46,XX+13 indicate?

A
  • 46 chromosomes
  • XX - the extra chromosome
  • 13 - at which chromosome
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7
Q

What problems arise in non-disjunction?

A
  • 1st stage: homologous pair not separated

- 2nd: sister chomatids fail to separate - one cell is disomy (2 copies)

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8
Q

What is an example of an autosomal aneuploidy syndrome?

A

-Trisomy 21 (down)

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9
Q

What does non-dysjunction cause?

A

Autosomal aneuploidy syndromes - Down, Patau, Edwards (only ones that survivable)

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10
Q

Examples of sex chromosomes aneuploidy syndromes?

A
  • Turner

- Klinefelter

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11
Q

Examples of structural abnormalities

A
  • Balanced/unbalanced rearrangements
  • Translocations
  • Deletions
  • Insertions
  • Inversions
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12
Q

Describe balanced translocations

A

Two non-homologous undergo reorganisation - retains same amount of DNA so no severe effects

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13
Q

Describe unbalanced translocations

A

Reorganistion leads to:
-Partial trisomy (extra chromosome)
-Partial monosomy (chromosome missing)
of each chromatid

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14
Q

Describe Robertsonian translocation

A

Translocation where two acrocentric chromosomes are fused but no DNA is lost

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15
Q

What happens in R translocation?

A

Two Q arms join, and two P arms join (usually lost)

-Unbalanced trans. leads to trisomy and monosomy

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16
Q

What is an acrocentric chromosome?

A

Centromere located near one end of the chromosome

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17
Q

Describe deletion mutations

A

Interstitial break in chromosome leading to deleted genetic material

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18
Q

Describe inversion mutations

A

Interstitial break in chromosome and inverted - no loss of DNA (balanced)

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19
Q

Name and describe the two types of inversion mutations

A
  • Paracentric - on the arms

- Pericentric - around centromere

20
Q

Examples of genetic mutations

A
  • Germline or somatic
  • Gene disruption
  • Polymorphism
21
Q

Types of genetic mutations

A
  • Non coding

- Coding

22
Q

Give examples of coding mutations

A
  • Silent - no change to AA
  • Missense - change of AA
  • Nonsense - stop codon leading to truncated protein
  • Frameshift -deletion/insertion
23
Q

Cys64Arg

A

AA 64 changed from cys to arg

24
Q

M252X

A

AA 252 codes sor stop codon

25
Q

1294del40

A

At AA 1294 theres a deletion of 40 nucleotides

26
Q

662-42C>T

A

42 nucleotides BEFORE 662 change from C to T

27
Q

IVS2+12insG

A

12 nucleotides into exon theres an insertion of G

28
Q

Methods of detecting mutations

A
  • PCR
  • Gel electrophoresis
  • RFLP
  • ARMS
  • DNA sequencing
29
Q

What is PCR used for

A

Amplifying small segments of DNA

30
Q

What is required for PCR?

A
  • Oligonucleotide primers
  • DNA sample
  • DNA polymerase (heat resistant)
31
Q

What are the step in PCR?

A
  1. Denaturing: DNA heated into 2 strands (break H bonds)
  2. Annealing: temp lowered so DNA primer attached to template DNA
  3. Extending: temp increase and DNA polymerase enzyme forms new strand
32
Q

What is the principle of gel electrophoresis?

A

Separating DNA fragments by size

33
Q

Mechanism of gel electrophoresis

A
  1. Apply an electric field
  2. DNA negatively charged due to -ve phosphate backbone and so moves towards +ve electrode
  3. Separate through agarose gel matrix
  4. Visualise DNA fragments
34
Q

PCR and gel electrophoresis

A

Gel used to visualised the results of PCR

35
Q

PCR applications

A
  • DNA cloning/sequencing
  • Gene identification
  • Mutation detection
36
Q

What is the use of ARMs?

A

To differentiate between wild type (normal) and mutant alleles

37
Q

Normal primer + wild type allele

A

Amplification

38
Q

Normal primer + mutant allele

A

No amplification

39
Q

Mutant primer + wild type allele

A

No amplification

40
Q

Mutant primer + mutant allele

A

Amplification

41
Q

What can ARMs be used in combination with?

A

PCR and Gel electrophoresis

42
Q

What is a disadvantage of PCR?

A

Primer design is critical - need to know what mutation codes for condition

43
Q

What are restriction endonucleases?

A

They’re enzymes from bacterial cell that degrade the DNA of invading viruses and recognise specific DNA sequences

44
Q

What is RFLP analysis?

A

Use of restriction endonuclease to cut specific section of DNA and run through gel electrophoresis

45
Q

What can RFLP analysis diagnose?

A

Sickle cell anaemia - use mutant primer in PCR to show mutant base

46
Q

What is DNA sequencing?

A

Chain termination method using dideoxynucelotides - from 5’ to 3’ end

PoD (35 decks)

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