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ESA1 - Medical Cell Biology and Genetics > Chromosomal Abnormalities > Flashcards

Chromosomal Abnormalities Flashcards

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1
Q

What is cytogenetics?

A

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

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2
Q

Why would someone be referred to cytogenetics?

A
  • Prenatal diagnosis
  • Birth defects
  • Abnormal sexual development
  • Infertility
  • Recurrent fetal loss (3 or more)
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3
Q

What is involved in chromosome analysis?

A
  • Count the number of chromosoms
  • Identify each chromosome pair
  • Assess if there is any missing/extra material
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4
Q

What is aneuploidy?

A

Loss/gain of whole chromosomes - abnormal number of chromosomes in a cell

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5
Q

How does aneuploidy arise?

A

Errors in meiosis

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6
Q

What is Down syndrome?

A

Trisomy 21

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7
Q

What is Patau syndrome?

A

Trisomy 13

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8
Q

What is Edwards syndrome?

A

Trisomy 18

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9
Q

What is Turner syndrome?

A

45, X

Only one normal X chromosome, rather than two

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10
Q

What is polyploidy?

A

Gain of a whole haploid set of chromosomes
Triploidy 3n
Usually spontaneously aborts

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11
Q

What is the main cause of polyploidy?

A

Fertilisation of an egg by more than one sperm

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12
Q

How is aneuploidy caused?

A

Originates from non-disjunction at one of the meiotic cell divisions, forming gametes with a missing chromsome and an extra chromosome

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13
Q

What happens when aneuploidy occurs during mitotic cell division?

A

Causes mosaicism (two cell populations in an individual)

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14
Q

What is anaphase lag?

A

Chromosomes can be left behind at cell division because of defects in spindle function or attachment of chromosomes leading to the loss of a chromosome

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15
Q

What are some characteristics of individuals with Down syndrome?

A

Characteristic facial features, intellectual disability, heart defects, early alzheimers

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16
Q

What are some characteristics of individuals with Edward syndrome?

A

Small lower jaw, rocker bottom feet, overlapping fingers

17
Q

What are some characteristics of individuals with Patau syndrome?

A

Multiple congential abnormalities, polydactyly, holoprosencephaly

18
Q

Why is a single X chromosome a problem?

A

Turner syndrome patients will be monosomic for genes in the PARs. SHOX gene (within PAR) associated with short stature.

19
Q

What are some characteristics of individuals with Turner syndrome?

A

Short sstature, heart defects, mild learning disabilities, neck webbing, infertility

20
Q

What is mosaicism?

A

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

21
Q

What does the degree of mosaicism depend on?

A 
When mitotic error occured:
First post zygotic division
-no mosaicism looks like a meiotic event
Subsequent divisions
-3 cell lines, monosomy cell line usually lost
22
Q

What are reciprocal translocations?

A

Reciprocal translocations are usually an exchange of material between nonhomologous chromosomes. No loss of genetic material.

23
Q

What chromosome mutations are there within one chromosome?

A

Deletion, duplication, inversion, ring chromosome, isochromosome

24
Q

What is an isochromosome?

A

Creation of two non identical chromosomes, one is a combination of the two short arms and the other is a combination of the two long arms

25
Q

What is a ring chromosome?

A

Loss of telomeres or ends of both arms and formation of a ring

26
Q

What chromosome mutations are there within two chromosomes?

A

Inversion, reciprocal translocation and robertsonian translocation

27
Q

What are robertsonian translocations?

A

Rearrangement of genetic material between two chromosomes; the q arm of two acrocentric chromosomes combine to form one ‘super chromosome’ with the loss of both p arms

28
Q

What is the largest and smallest chromosome?

A 
Largest = 1
Smallest = 22
29
Q

On which chromosomes can robertsonian translocations occur?

A

13, 14, 15, 21, 22

30
Q

What is microarray comparative genomic hybridisation?

A

Examine the whole genome at high resolution

ESA1 - Medical Cell Biology and Genetics (18 decks)

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