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RACP Written > Genetics > Flashcards

Genetics Flashcards

1
Q

Which two syndromes are associated with a cherry red macula?
(Hint: they both have also developmental regression)

A

Neimann Pick Type 1 OR Tay Sachs disease
Tay Sachs disease is a lysosomal storage disorder that presents after 3 months with regression of gross motor skills. Macrocephaly is common because of accumulation of GM2 ganglioside in the brain. Niemann Pick Disease Type A is also associated with developmental regression and a cherry red macula but reflexes are absent or reduced. Macrocephaly is not a usual feature.

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2
Q

What are the 4 base pairs in DNA and what is the pairing?

A

Adenine
Thymine
Cytosine
Guanine
A-t, C-G

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3
Q

How many hydrogen bonds between G and C?

A

3

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4
Q

What percentage of the genome is protein encoding genes?

A

1-2% are exons

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5
Q

How many base pairs in the genome?

A

3 billion

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6
Q

What are the 4 phases of Miosis?

A

Prophase- duplication of chromosomes
Metaphase- chromosomes align at central plate
Anaphase: sister chromatids separate
Telophase: separate into 2 cells

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7
Q

What happens in Prophase 1?

A

Chromosomal duplication AND binding of homologous chromosomes to form tetrameres

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8
Q

What happens in Metaphase 1?

A

Tetrads align in the centre.

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9
Q

What happens in telo and anaphase 1?

A

Homologous chromosomes are separated, but sister chromatids remain together.

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10
Q

What happens in meiosis II?

A

Sister chromatids separate so there is HALF the number of chromsomes now in the daughter cells vs parent cells

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11
Q

What is the result of chromosomal non disjunction?

A

Aneuploidy. Essentially, the chromosomes dont separate so get one egg with 2 chromsomes and one with none.

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12
Q

What is the role of helicase, ligase and DNA polymerase?

A

Helicase unzips DNA
Ligase fills in gaps
Polymerase copies- 5’ to 3’ in leading and other way around in lagging strand

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13
Q

Where are promoter regions?

A

Upstream at 5’ end of the first exon, often contains TATA box

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14
Q

Where are enhancer or silencor regions?

A

Can be anywhere, further modify expression

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15
Q

What are the 3 consequences of a base substitution?

A

Silent/synonymous mutation
Nonsense: premature stop codon
Missense: change in amino acid

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16
Q

What is the conseuqence of deletions and insertions?

A

Alter reading frame, resulting in completely diff sequence of amino acid

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17
Q

What is the difference between penetrance and expressivity?

A

Penetrance is if you have he phenotype or not,
Expressively is HOW much of the phenotype you have.

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18
Q

What is the baseline risk of having an autosomal recessive condition/ a syndrome?

A

3%

19
Q

What is the risk of a serious syndrome/recessive condition in consanguineous marraiges?

A

Double, 6%

20
Q

Why is it clinically important to check the genetic cause of T21?

A

Unbalanced trans location between 4:21 means that there is extra 21 chromosome and one of the parents can be a carrier, pass onto next child

21
Q

What are 5 features of Klienfelters?

A

hypogonadism, low testosterone, infertility, incomplete virilisation, gynaecomastia, tall stature, mild learning disabilities, emotioanlly immature, shy

22
Q

What is the number one cause of male hypogonadism?

A

Klienfelters

23
Q

What are the main features of Turners?

A

Webbed neck, infertility, short stature, NORMAL inellect

24
Q

What are the cardiovascular defects associated with Turners?

A

Coarctation of aorta, bicuspid aortic valve

25
Q

What is an example of a condition that has issues with copy number variants?

A

Retts

26
Q

What is the carrier risk in a sibling of an individual WITH a recessive condition?

A

2/3

27
Q

Name 2 X linked dominant conditions

A

X linked hypophosphataemic rickets, incontinentia pigmenti

28
Q

What is anticipation in the context of genetics and triplet repeat disorders?

A

Phenotype worsens in subsequent generations as you inherit more and more triplet repeats

29
Q

What is the risk of atopy in child if parent has it?

A

50%.
This increases to 66% if both parents have it or if two first degree relatives have

30
Q

What are contigous gene syndromes?

A

group of disorders in which a small deletion or duplication of genetic material that contains multiple genes causes a recognizable phenotype.

ie Prader-Willi syndrome (PWS), Angelman syndrome (AS), and Williams syndrome (WS). Another disorder, 22q11.2 deletion syndrome

31
Q

What are contigous gene syndromes?

A

group of disorders in which a small deletion or duplication of genetic material that contains multiple genes causes a recognizable phenotype.

ie Prader-Willi syndrome (PWS), Angelman syndrome (AS), and Williams syndrome (WS). Another disorder, 22q1What1.2 deletion syndrome

32
Q

What is a good diagnostic test for Smith Lemli Opitz syndrome?

A

7-dehydrocholesterol

33
Q

What is the minimum number of repeats req to display Fragile X?

A

> 200
between 55-200 is asymtpmatic, premutation carriers

34
Q

What is epigenetics?

A

Change in how DNA is read, NOT actual change to the DNA

35
Q

What is the gene/locus affected for Prader Willi and Angelman?

A

15q11.2-q13

36
Q

What is imprinted in Prader-Willi Syndrome?

A

Paternal Imprinting.
P for PATERNAL
(Remember Angelman and Prada linked, Angel wears Prada which is 15x more expensive that silver)

37
Q

What is imprinted in Angelman syndrome?

A

Maternal imprinting
(Remember Angelman and Prada linked, Angel wears Prada which is 15x more expensive that silver)

38
Q

What is the gene for Russel Silver and BWS?

A

11p15
Codes for IGF2 and is a paternally expressed growth factor.

39
Q

What is imprinted in BWS?

A

MATERNAL imprinting.
If you dont have mum’s genes, tend to be BIG like a MAN
(remember BWS and Russel Silver linked)
(Remember Angelman and Prada linked, Angel wears Prada which is 15x more expensive that silver)

40
Q

What is imprinted in Russel Silver?

A

PATERNAL imprinting
Dont have dad’s genes so small and petite

41
Q

What is imprinted in Russel Silver?

A

PATERNAL imprinting
Dont have dad’s genes so small and petite(remember BWS and Russel Silver linked)

42
Q

What is the familial risk for ASD for sibling?

A

Twins: 60%
Siblings: more recently >10% recurrence 2 siblings with ASD >20%

43
Q

What is the difference between Cohen syndrome and Prada-Willi?
Hint- Who can’t see?

A

Both have hypotonia and truncal/central obesity in later periods.

Cohen: Also has vision problems, beak nose, retinopathy, neutropenia. ‘COHEN CANNOT SEE’
Prader Willi: Has almond shaped eyes, severe hypotonia and feeding difficulty in early neonatal period, OCD and genital hypoplasia.

RACP Written (18 decks)

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