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Disease Processes > Chromosome Syndromes > Flashcards

Chromosome Syndromes Flashcards

1
Q

Define Non-Dysjunction

A

Process of mis-division during meiosis & mitosis that brings about Aneuploidy in a cell.

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2
Q

Define Aneuploidy

A

An abnormal number of chromosomes in a cell.

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3
Q

Define Chromatin

A

Unwound Chromosome, ready for meiosis or mitosis.

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4
Q

Define Homologous pair of Chromosomes

A

A pair of chromosomes that contain the same genes but different alleles due to one being paternal and the other maternal.

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5
Q

Define centrosomes

A

An organelle near the nucleus that contains centrioles that forms the spindle fibres during cell division. (Also replicates like chromosomes before division)

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6
Q

What occurs in Interphase?

A

Homologous chromosomes replicate and are attached together by centromere. Organelles (centrosomes) also replicate.

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7
Q

What occurs during Prophase l?

A

Nuclear envelope disappears and spindle fibres form, homologous pairs line up and genetic recombination occurs.

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8
Q

What occurs during Metaphase l?

A

Spindle fibres attach to kinetochore (complex of proteins associated with centromere) of each chromosome.

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9
Q

What occurs during Anaphase l?

A

Just the homologous pairs separate from eachother (stay attached to replicate by centromere). Move to opposite pole of the cell.

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10
Q

What occurs during Telophase l?

A

The microtubules (spindle fibres) disassemble. Cytokinesis occurs (cytoplasm splits). Nuclear envelope forms again. Each of the two cells has half the number of chromosomes, still attached by centromere.

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11
Q

What occurs in Prophase ll?

A

Nuclear envelope disintegrates again. Centrosomes push apart in separate directions to form spindles.

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12
Q

What occurs during Metaphase ll?

A

Spindle fibres attach to centromeres. The chromosomes line up.

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13
Q

What occurs in Anaphase ll?

A

The spindle fibres splits the sister chromatids from the centromere to opposite poles = single chromosomes.

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14
Q

Define Uniparental disomy

A

2 copies of a chromosome come from same parent instead of one from each (maternal & paternal).

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15
Q

Describe the symptoms of Down’s Syndrome (Trisomy 21).

A 
Hypotonic (floppy when baby)
Poor reflexes
Joints are hyper flexible
Pelvic dysplasia
Flat face
Small ears
Large tongue
Simian Crease (single crease down palm)
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16
Q

What’s the risk of incidence of Down’s?

A

1/600-1/700

17
Q

What’s the percentage risk for Down’s?

A

94% regular

  1. 5% translocation from 13,15,21
  2. 5% mosaic
18
Q

Describe the symptoms of Edward’s Syndrome.

A 
Feeble foetal activity
Pelvic dysplasia 
"Rocker bottom" feet
Neurological disorders
Survive up to 2 years Maximum
19
Q

What’s the risk of incidence in Edward’s syndrome?

A

1/3000-1/4000 live births

3 females: 1 male

20
Q

What’s the life expectancy of a patient with Edward’s syndrome?

A

3-6 months unless mosaic

21
Q

What’s the percentage risk of Edward’s syndrome?

A

90% regular

10% mosaic

22
Q

Describe the symptoms of Patau’s Syndrome.

A 
Severe neurological deficiencies 
Cardiac abnormality
Retinal dysplasia
Severe cleft lip and palate 
Deafness
23
Q

What’s the risk of incidence for Patau’s syndrome?

A

1/5000 live births

24
Q

What’s the percentage risk of Patau’s syndrome?

A

75% regular
20% translocation
5% mosaic

25
Q

Name the other non-dysjunctions

A

Trisomy 16- lethal, spontaneous abortion at 13 weeks
Trisomy 8- very rare, lethal unless mosaic
Trisomy 9- very rare, majority die in early post natal

26
Q

What is Turners syndrome?

A

Monosomy X (X inactivation)

27
Q

Describe the symptoms of Turner’s syndrome

A 
Short stature
Lack of secondary sexual characteristics
Infertile
Webbed neck
Variable IQ
Can be colourblind
28
Q

What’s the risk of incidence of Turner’s syndrome?

A

1/4000 live female births

29
Q

List the prenatal diagnostic methods for chromosomal disorders

A 
Amniocentesis
Chronic villus biopsy
IVF/ pre implantation diagnosis
Bart's test- maternal blood sample, testing for proteins
Mucosal membrane scan 
Colourblindness as a marker
30
Q

What’s the percentage of sex chromosome abnormalities?

A

70% paternal

30% maternal

31
Q

What’s the percentage of autosomal abnormalities?

A

90% maternal

10% paternal

Disease Processes (14 decks)

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