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Genetics > Aneuploidies > Flashcards

Aneuploidies Flashcards

1
Q

What is an aneuploidy?

A

A chromosomal abnormality caused by an abnormality in chromosome number

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2
Q

What is an abnormality in chromosomal number known as?

A

Aneuploidy

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3
Q

What causes Edward’s syndrome?

A

Trisomy 18 - it is an aneuploidy

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4
Q

What causes Patau’s syndrome?

A

Trisomy 13 - it is an aneuploidy

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5
Q

What causes Kleinfelter’s syndrome?

A

XXY - it is an aneuploidy (an additional X chromosome in an XY individual

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6
Q

What causes the majority of trisomies?

A

Non-dysjunction at meiosis 1 (>70%)

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7
Q

What causes Turner’s syndrome?

A

45X0 = a monosomy X, an aneuploidy (abnormality in chromosomal number)

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8
Q

What proportion of trisomies are secondary to mosaicism?

A

<5%

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9
Q

What is the overall prevalence of Down’s syndrome?

A

1 :700 - 80% undergo spontaneous miscarriage

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10
Q

What proportion of Down’s syndrome is secondary to mosacism?

A

1%

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11
Q

How many chromsomes does a patient with Down’s syndrome have?

A

47

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12
Q

What does trisomy 18 cause?

A

Edward’s syndrome

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13
Q

What does trisomy 13 cause?

A

Patau’s syndrome

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14
Q

What is the most common mechanism that leads to trisomy?

A

Non-disjunction at meiosis 1

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15
Q

What proportion of Down’s syndrome is caused by Robertsonian Translocation?

A

4%

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16
Q

Which chromosomes are involved in Robertsonian Translocation in Down’s syndrome?

A

14 and 21

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17
Q

Risk of Down’s syndrome in a mother is 40 years old

A

1 in 100

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18
Q

Which cancers are Down’s syndromes patients at risk of?

A

Acute myeloid and acute lymphoblastic leukaemia

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19
Q

Which heart defects are associated with Down’s syndrome?

A

Ventricular septal defect
Atrial septal defect
Atrio-ventricular septal defect

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20
Q

Which GI problems are associated with Down’s syndrome?

A

Duodenal atresia
Imperforate anus
Hirsprung’s disease

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21
Q

What neurological condition are Down’s syndrome patients at risk of developing in adulthood?

A

Alzheimers disease

22
Q

How are screening blood tests altered in Down’s syndrome pregnancies?

A

Unconjugated E3, PappA and AFP are reduced

Inhibin A and Beta HCG are increase

23
Q

What endocrinological condition is associated with Down’s syndrome?

A

Hypothyroidism

24
Q

What is the cut of risk for invasive screening for Down’s syndrome?

A

A risk equal or greater than 1 in 250

25
Q

What is the prevalence of Edward’s syndrome?

A

1 in 3000 (95% die before birth)

26
Q

What are the facial features of Edward’s syndrome?

A

Micrognanthia (small chin)
Cleft lip and palate
Low set ears

27
Q

What are the musculoskeletal defects seen in Edward’s syndrome?

A

Rocker bottom feet

Overlapping fingers

28
Q

Which cardiac defects are associated with Edward’s syndrome?

A

Septal defects - VSD and ASD

Patent ductus arteriosus

29
Q

What is the mortality rate associated with Edwards syndrome after birth?

A

90% within 1 year

30
Q

What are the intrabdominal defects associated with Edwards syndrome?

A

Exomphalos
Inguinal hernia
Diaphragmatic hernia
Renal malformations

31
Q

What is the prevalence of Patau’s syndrome?

A

1 in 5000 births

32
Q

What is the mortality rate for Patau’s syndrome?

A

100% within 1 month of age

33
Q

What is the median survival for Patau’s syndrome?

A

less than 3 days

34
Q

What are the facial features of Patau’s syndrome?

A

Cleft palate and lip

Hypotelorism - abnormally decreased distance between the eyes

35
Q

What are the cerebral defects associated with Patau’s syndrome?

A

Holoprosencephaly

36
Q

What are the musculoskeletal features of Patau’s syndrome?

A

Polydactyl

Rocker bottom feet

37
Q

Which heart defects are commonly associated with Patau’s syndrome?

A

VSD, ASD, PDA, dextrocardia

38
Q

Which hormonal abnormality is associated with Kleinfelters syndrome?

A

Decreased testicular testosterone and inhibin production, resulting in increased LH and FSH production

39
Q

Which cells does LH affect in the testicles?

A

Leydig cells

40
Q

Which cells does FSH affect in the testicles?

A

Sertoli cells

41
Q

What does LH stimulate the testicular cells to produce?

A

LH stimulates Leydig cells to produce testosterone from cholesterol

42
Q

What are the Sertoli cells located in the testes?

A

In the seminiferous tubules

43
Q

Where are the Leydig cells located in the testes?

A

In the interstitium

44
Q

Which hormone is released by Sertoli cells?

A

Inhibin

45
Q

What is the prevalance of Kleinfelter’s syndrome?

A

1 in 1000 births

46
Q

What are the clinical features of Kleinfelter’s syndrome?

A 
Small testes
Tall
Failure to develop secondary male sex characteristics
Infertility
Transient gynaecomastia
47
Q

Which diseases are kleinfelters syndrome patients more at risk of developing than normal XY phenotypes?

A

Breast cancer

Osteoporosis

48
Q

What is the prevalence of Turner’s syndrome?

A

1 in 2500 live female births

49
Q

What are clinical features of Turner’s syndrome?

A 
short stature
Hypogonadism - amenorrhoea
Increased nuchal translucency
Distal lymphoedema
Neck webbing
Cystic hygroma
shield shaped chest
Horseshoe kidney
Coarctation of the aorta
Osteoporosis
50
Q

What are the hormonal abnormalities in Turner’s syndrome?

A

Low oestrogen and progesterone

Genetics (4 decks)

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