MCGB - Chromosome Abnormalities Flashcards Preview

CJ: UoL Medicine Semester One (ESA1) > MCGB - Chromosome Abnormalities > Flashcards

Flashcards in MCGB - Chromosome Abnormalities Deck (22)
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1
Q

What is cytogenetics?

A

Study of the genetic constitution of cells through the visualisation and analysis of chromosomes

2
Q

Give some reasons for cytogenetic analysis to be carried out.

A
  • accurate diagnosis/prognosis of clinical problems
  • better clinical management
  • assess future reproductive risks
  • prenatal diagnosis
3
Q

What are “constitutional abnormalities”?

A

They are a reason for referral for cytogenetic analysis - includes prenatal diagnosis, birth defects, infertility etc

4
Q

What are “acquired abnormalities”?

A

Also referral reason for cytogenetic testing - include leukaemias, solid tumours etc

5
Q

Give two prenatal diagnosis methods.

A
  • chorionic villus sampling (11-12 weeks, 1.2% miscarriage risk)
  • amniocentesis (15+ weeks, 0.8% miscarriage risk)
6
Q

Give some examples of birth defects that can be identified by prenatal screening.

A

Dysmorphism, congenital malformations, mental retardation, developmental delay, specific syndromes (eg. Downs, Williams, DiGeorge)

7
Q

What is the name of this procedure?

Metaphase chromosomes are stained, paired up and grouped together. Abnormalities are identified and described.

A

Karyotyping

8
Q

Give an example of a disorder caused due to trisomy.

A

Down’s syndrome (+21), Patau syndrome (+13), Edwards syndrome (+18)

9
Q

Give a disorder caused by monosomy.

A

Turner syndrome (only one X)

10
Q

What is polyploidy?

A

Gain of a whole haploid set of chromosomes, like trisomy but for entire set of chromosomes. Usually spontaneously aborts during pregnancy.

11
Q

What is the most common cause of polyploidy?

A

Polyspermy - fertilisation of an egg by more than one sperm.

12
Q

What is it called when chromosomes are “left behind” at cell division due to defects in spindle function?

A

Anaphase lag

13
Q

What is Edwards syndrome?

A

Trisomy 18. Usually only live 5-15 days, symptoms are rocker bottom feet, low-set ears, overlapping fingers, small lower jaw.

14
Q

What does trisomy 13 cause?

A

Patau syndrome

15
Q

What is Turner syndrome?

A

Occurs when girls are born with one functioning X chromosome. Symptoms include puffy feet, redundant skin at back of neck, short stature

16
Q

What is mosaicism?

A

Presence of 2 or more cell lines in an individual, usually caused by mitotic non-disjunction.

17
Q

Give some examples of cytogenetic structural abnormalities.

A
  • translocations
  • inversions
  • deletions
  • duplications
  • insertions
18
Q

What are reciprocal translocations?

A

Exchange of material between two chromosomes, eg part of chromosome 4 breaks off and is swapped with part of chromosome 18.

19
Q

What is a Robertsonian translocation?

A

Participating chromosomes break at their centromeres and the long arms fuse to form a single, large chromosome with a single centromere.

20
Q

What is the benefit of using a whole chromosome paint?

A

Can identify individual chromosomes even when they are rearranged.

21
Q

What does microarray comparative genomic hybridisation do?

A

Examines the whole genome at high resolution, comparing normal control DNA to patient DNA.

22
Q

Give an anvantage and a disadvantage of array CGH.

A

+ examines entire genome
+ targeted against known genetic conditions

  • more expensive than karyotyping
  • does not detect balanced re-arrangements

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