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Jonathan's Reproduction > Clinical Genetics > Flashcards

Clinical Genetics Flashcards

1
Q

T/F A significant portion of the genome codes for proteins

A

False, very little of the genome actually codes for proteins

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2
Q

What is the main role of heterochromatin region?

A

condensing DNA
gene regulation
protect integrity of DNA

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3
Q

What are some of the regulatory products coded by the genome?

A

tRNA, rRNA, non-coding RNAs

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4
Q

Which process complex is responsible for the splicing of RNA?

A

Slicesosomes, important for generating diversity

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5
Q

How does histone regulate expression?

A

it winds more or less tightly via acetylation and methylation, allowing or denying access of replicating machinery

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6
Q

What’s euchromatin?

A

the open conformation of chromosome (heterochromatin is closed)

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7
Q

What is DNA methylation associated with?

A

Silencing genes

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8
Q

What is the CpG region also known as?

A

CpG islands, because they are rich around promotor regions

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9
Q

How is CpG island related to silencing of the genome

A

when it’s hyper-methylated + low acetylation of histone, the gene is silenced

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10
Q

T/F Euchromatins have hypermethylated CpG islands

A

False, euchromatins are open, allowing replication. So CpGs are lacking methylation, while histones are hypermethylated

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11
Q

What are some ways of generating genome and protein diversity?

A

having more than one promotor on one gene

alternative splicing from the same transcript

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12
Q

What are some roles of non-coding RNAs?

A

act as decoy
scaffold,
guide transcription factor
enhancer

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13
Q

What are short interfering RNAs made from?

A

double stranded RNAs

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14
Q

What is the action of short interfering RNA

A

Interact with RNA-induced silencing complex to increase degradation of mRNA

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15
Q

What is the function of micro-RNAs?

A

interact with RISC to repress translation rather than degrade mRNAs

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16
Q

What is bi-allelic expression?

A

Where both maternal and paternal copy need to transcribe equal amount of proteins at a time

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17
Q

What is trisomy 21 also known as?

A

Down syndrome

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18
Q

What are the symptoms of down syndrome?

A

mental disability

congenital heart disease, GIT disease, increased risk of leukemia, early onset Alzheimer

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19
Q

What is trisomy 18 also known as?

A

Edwards Syndrome, with severe mental disability, limb and heart defects

20
Q

What are some autosomal recessive conditions?

A

cystic fibrosis, sickle cell anaemia, thalassaemia, haemochromatosis

21
Q

What is haplo-insufficiency?

A

When there is only one copy of the chromosome and not enough protein is produced.

Autosomal dominant condition

22
Q

When does X-chromosome inactivation occur?

A

around 8 cell stage

23
Q

What is the Barr body?

A

condensed chromosome on X-inactivation

24
Q

How does X-inactivation occur?

A

due to non-coding RNA Xist expression, which creates a wave of hyperchromatin in both directions

25
Q

What is Turner syndrome?

A

45X, where one X is missing. There are a few genes that must remain active

26
Q

Which genes of the inactivated X genes must remain active?

A

genes that cluster at the ends of the chromosome, homologous to the Y chromosome

27
Q

What are genomic imprinted genes?

A

genes that are expressed in parent-specific manner. The maternal and paternal genes come together during fertilisation

28
Q

What is parthenogenesis and androgenesis?

A 
parthenogenesis = all maternal origin chromosomes 
androgenesis = all paternal origin chromosomes
29
Q

T/F Maternal genes tend to conserve resource for the mother

A

True

30
Q

What are the four causes of imprint disorders?

A

large deletion/duplication of chromosomes with imprint genes

Uniparental disomy

Epimutation

DNA mutation

31
Q

What is uniparental disomy?

A

extra chromosome from either mother or father

32
Q

What is Beckwith-Widemann syndrome?

A

overgrowth due to mostly sporadic epimutation on maternal allele

33
Q

What is Prader-Willi syndrome?

A

Overgrowth due to

1) deletion of paternally inherited C15
2) maternal uniparental disomy

34
Q

What is Angelman syndrome due to?

A

deficiency in maternally-imprinted genes

35
Q

What is the first step of prenatal testing?

A

take a 3 generation family history to look for any inherited condition, recurrent miscarriages, or unexplained perinatal deaths

36
Q

When does the risk of down syndrome increase in relation to maternal age

A

30

37
Q

What is the reason for prenatal testing?

A

Offer choice in order to help patients make better decisions

38
Q

What does the first trimester screen involve?

A

Biochemical test at 10 weeks, ultrasound at 11-13 weeks, and nuchal translucency

39
Q

What is nuchal translucency?

A

Fluid behind baby’s neck. Thick fluid is not normal

40
Q

What does 1st and 2nd trimester screening look for?

A

Trisomy 21 and 18

Down syndrome and Edwards syndrome

41
Q

What does the 2nd trimester screening involve?

A

blood test at 15-17 weeks + maternal age to work out risk algorithm

42
Q

What is the 2nd trimester a good screening tool for?

A

neural tube defect

43
Q

What are the diagnostic tests offered to women with high risk of birth defect?

A

Chorionic villus sampling at 11 weeks

Amniocentesis at 15 weeks

44
Q

What does Chorionic villus sampling involve?

A

insert needle into placenta to get tissue from embryonic placenta

45
Q

What is fluorescence in situ hybridisation for?

A

test on the cells collected by CVS and amniocentesis

46
Q

What are the three ways of analysing collected tissue from CVS and amniocentesis

A

FISH
Karyotype
Microarray

Jonathan's Reproduction (15 decks)

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