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MCBG > Chromosomal Abnormalities, Sickle Cell, Huntington's > Flashcards

Chromosomal Abnormalities, Sickle Cell, Huntington's Flashcards

1
Q

What are two methods of prenatal diagnosis?

A

Chorionic villus sampling

Amniocentesis

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2
Q

What is aneuploidy?

A

Loss/gain of whole chromosomes –> wrong number of chromosomes

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3
Q

What is an example of a trisomic disorder?

A

Downs syndrome (chromosome 21)

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4
Q

What is the only example of a monosomic disorder that is viable for life?

A

Turner syndrome (girls with 1 X chromosome)

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5
Q

What is polyploidy? What is the most common cause for polyploidy?

A

The gain of a whole haploid set of chromosomes - usually lethal

Fertilisation of egg by more than 1 sperm

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6
Q

What is anaphase lag? What causes it?

A

Where chromosomes are ‘left behind’ at cell division

Defects in spindle function/attachment to spindle chromosomes

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7
Q

Why is x chromosome monosomy the only example of monosomy that is viable for life? Why are there still problems caused by X chromosome monosomy?

A

Due to X chromosome inactivation

PAR1 and PAR2 regions need to be active in both chromosomes

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8
Q

What is mosaicism?

A

The presence of 2 or more cell lines in an individual

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9
Q

What causes mosaicism?

A

Mitotic nondisjunction

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10
Q

What are two types of chromosome translocations?

A

Reciprocal translocation

Robertsonian translocation

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11
Q

What is reciprocal translocation?

A

2 break rearrangements between non homologous chromosomes

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12
Q

What is a robertsonian translocation?

A

Rearrangement of parts of chromosomes between acrocentric chromosomes

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13
Q

Why do robertsonian translocations result in a chromosome count of 45?

A

The two p arms of the acrocentric chromosomes fuse together and don’t contain much genetic information and are therefore lost

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14
Q

What is a balanced chromosomal arrangement?

A

No missing genetic material, just rearranged

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15
Q

What is chromosomal imbalance?

A

Where there are missing chromosomes or extra genetic material (e.g. Deletions)

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16
Q

How can microdeletions/duplications be identified if they cant be seen by banding at karyotyping?

A

By using FISH

17
Q

What is uniparental disomy?

A

Presence of homologous chromosomes from one parent

18
Q

What is isodisomy?

A

2 identical chromosomes from 1 parent

19
Q

What is heterodisomy?

A

2 homologous chromosomes from 1 parent

20
Q

What are imprinted chromosomes? Where can they cause problems?

A

Chromosomes that show differential gene expression depending on whether they are from the mother or father

During uniparental disomy

21
Q

How can UPD be generated?

A

Monosomy rescue
Trisomy rescue
Gamete complementation
Mitotic error

Any 2 of these

22
Q

What are symptoms of sickle cell anaemia?

A

Fever
Anaemia
Severe pain

Sudden death

23
Q

What sort of treatment is used for sickle cell anaemia?

A

Treatment based on limiting the symptoms

24
Q

Individuals that are heterozygous for the B-globin mutation that causes sickle cell anaemia will have…

A

A mild form of the disease called Sickle Cell Trait

25
Q

Which populations is sickle cell anaemia common in?

A

African populations

26
Q

What advantage results from having sickle cell trait?

A

Individuals are usually resistant to the most lethal forms of malaria

27
Q

What does epigenetics involve?

A

Turning genes on or off that code for transcription factors

28
Q

How can epigenetics be used to treat sickle cell anaemia?

A

If you can delete the gene that inactivates the gamma-globin gene after birth, there would be increased levels of gamma-globin and decreased levels of beta-globin, minimising the negative effects of sickle cell anaemia

29
Q

What are the symptoms of Huntington’s?

A

Abnormal gait
Personality change
Dementia

30
Q

What type of mutation is seen in Huntington’s? In which gene?

A

Triplet repeat expansion

HTT gene

31
Q

How can Huntington’s be tested for?

A

PCR used to amplify CAG repeats sequence and then separate on gel to determine size

32
Q

What is the typical age of onset of Huntington’s?

A

40-50 yrs old

33
Q

How does Huntington’s develop between generations?

A

Earlier onset

More severe

34
Q

What is the relationship between age of onset and the number of CAG repeats?

A

Earlier age of onset = more repeats

35
Q

Why can epigenetics not be used to treat Huntington’s Disease?

A

The HTT gene is switched on in all humans

36
Q

The inhibition of which pathway was found to prevent Huntington’s Disease in yeast and fruit flies?

A

The kynurenine biochemical pathway

MCBG (15 decks)

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