Chromosomal abnormalities Flashcards

1
Q

What is cytogenetics?

A

Study of genetic makeup of cells through imaging of chromosomes

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2
Q

Why is cytogenetics done?

A

Accurate diagnosis

Future reproductive risks

Prenatal diagnosis

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3
Q

What are some examples as to why somebody may be referred to cytogenetics?

A

Birth defects

Infertility

Frequent miscarriages

Cancers

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4
Q

What are some examples of birth defects?

A

Congenital malformations

Mental retardaton
Developmental delay

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5
Q

How are chromosomes assessed on a visual karyotype?

A

Look at banding pattern

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6
Q

What is the genetic cause of Down syndrome?

A

Trisomy 21

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7
Q

What is the genetic cause of Edward syndrome?

A

Trisomy 18

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8
Q

What is the genetic cause of Patau syndrome?

A

Trisomy 13

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9
Q

What is the genetic cause of Turner syndrome?

A

45, X

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10
Q

Why do people with Turner syndrome manage to survive?

A

Because even in normal females, one X chromosome is inactivated, only one is active

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11
Q

What is polyploidy?

A

Gaining a whole haploid set of chromosomes

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12
Q

How many chromosomes are there altogether in polyploidy?

A

69

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13
Q

What is the main cause of polyploidy?

A

Polyspermy

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14
Q

What is polyspermy?

A

When one egg is fertilised by more than one sperm

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15
Q

What is anaphase lag?

A

Refers to how chromosome can be left behind at anaphase stage of cell division

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16
Q

What are the causes of anaphase lag?

A

Defects in spindle attachment to chromosomes

Defects in spindle function

17
Q

What happens to the lagging chromosome in anaphase lag?

A

Lost entirely

18
Q

What are some of the symptoms and signs of Down syndrome +21?

A

Characteristic facial features

Heart defects

Hypotonia

Intellectual disablity

19
Q

What are some of the symptoms and signs of Edwards syndrome +18?

A

Overlapping fingers
Rocker bottom feet

Prominent occipit
Small lower jaw
Low-set ears

20
Q

Is Edwards syndrome more common in male or females?

21
Q

What is the lifespan of a baby with Edwards syndrome?

A

Approx. 2 weeks

22
Q

What are some of the symptoms and signs of Patau syndrome +13?

A

Polydactyly

23
Q

What is the lifespan of a baby with Patau syndrome?

A

Most die as newborns

24
Q

Why does having only one X chromosome cause problems in Turner syndrome?

A

Some genes are not inactivated in the second X chromosome

Individuals with Turner syndrome lack these genes

25
What are the signs and symptoms of Turner syndrome?
Short stature Neck webbing Puffy feet Infertility
26
What is a reciprocal translocation?
Small part of two chromosomes broken off | swapped over
27
How are the gametes of somebody with a reciprocal translocation affected?
May be balanced May be unbalanced
28
What is meant by balanced?
All genetic material is present
29
What is meant by unbalanced?
Some genetic material is extra or missing
30
What is a Robertsonian translocation?
Two acrocentric chromosomes fused together
31
How many chromosomes do people with a Robertsonian translocation have?
45
32
What is formed in meiosis in people with a Robertsonian translocation?
Trivalent - three chomrosomes gives risk of aneuploidy
33
What will the phenotype of the unbalanced gamete depend on?
Which regions show monosomy and trisomy
34
What are the different types of FISH probes?
Gene specific probes Centromere probes Telomere probes Whole chromosome paints
35
What are gene specific FISH probes used for?
Identify microdeletions
36
What are centromere FISH probes used for?
Identify chromosome of origin
37
What are whole chromosome paints in FISH used for?
Identify chromosomal rearrangement
38
What can microarray comparative genomic hybridisation not detect?
Balanced rearrangements
39
What is formed in prophase 1 of meiosis in people with Reciprocal translocations?
Quadrivalent - four chromosomes