Chromosomal Abnormalities Flashcards

1
Q

What staining leaves a recognizable pattern of bands?

A

Giemsa staining.

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2
Q

What is the p arm?

A

Short arm of chromosome.

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3
Q

What is the q arm?

A

Long arm of chromosome.

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4
Q

What do the dark areas (heterochromatin) on a karyotype mean?

A

Highly condensed, gene-poor, and transcriptionally silent,

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5
Q

What do the light areas (euchromatin) on a karyotype mean?

A

Less condensed, gene-rich, and more easily transcribed

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6
Q

What is aneuploidy?

A

Abnormal number of chromosomes (not a multiple of 23).

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7
Q

What is non disjunction?

A

Uneven number of chromosomes in meiosis daughter cells. Results in +1 or -1 leading to trisomy and monosomy.

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8
Q

Most common form of aneuploidy?

A

Sex chromosome aneuploidy.

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9
Q

Why is sex chromosome aneuploidy better tolerated?

A

X chromosome inactivation of extra x chromosomes and low gene content of Y chromosome.

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10
Q

Why if extra x chromosomes are inactivated does sex chromosome aneuploidy still have an effect?

A

Both X and Y chromosome have a pseudo autosomal region.

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11
Q

How would you write the karyotype of an individual with trisomy 21?

A

47 +21 or 47,XX +21

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12
Q

What is the main cause of trisomy 21?

A

Maternal meiosis.

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13
Q

What increases the risk of trisomy 21 massively?

A

Age of the mother.

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14
Q

Why is maternal meiosis the main cause of trisomy 21?

A

As woman age the chromatids in the gametes they were born with become less organised. In males, sperm cell are continually generated.

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15
Q

What is mosaicism?

A

Presence of two or more population of cells with different genotype.

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16
Q

How can sex chromosome aneuploidy be an example of mosaicisim?

A

X chromosome becomes inactivated during early development.

17
Q

When does crossing over of chromatids occur?

A

Prophase I.

18
Q

What causes unequal crossover of chromatids?

A

Misalignment of homologous chromosomes.

19
Q

What can unequal crossover of chromatids cause?

A

Trinucleotide expansion.

20
Q

What can unequal crossover of chromosomes lead to?

A

Duplication and deletion of genes.

21
Q

If there is an unequal crossover of chromosomes but it is balanced what can result?

A

Carrier not affected but offspring can be affected. Offspring can be normal, balanced carrier or unbalanced (affected).

22
Q

What does philadelphia chromosome lead to?

A

CML (Chronic myeloid leukemia).

23
Q

What is philadelphia chromosome?

A

Chromosome 9 and 22 break and exchange portions.

24
Q

What is a metacentric chromosome?

A

Short arm and long arm are the same length.

25
Q

What is a submetacentric chromosome?

A

Short arm is shorter than long arm.

26
Q

What is an acrocentric chromosome?

A

Short arm encodes no genes.

27
Q

What is a Robertsonian translocation?

A

Two acrocentric chromosomes form one chromosome.

28
Q

When does a Robertsonian translocation cause problems?

A

If its unbalanced. Can cause problems in offspring.