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EMS - JL > 12,13,14 > Flashcards

12,13,14 Flashcards

1
Q

What is androgenesis

A

reproduction dependent on father

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2
Q

What is pathenogenesis

A

Reproduction dependent on the mother

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3
Q

What does retention of a polar body result in

A

Parthenogenesis 46XX

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4
Q

What happens if you get an empty egg fertilised by a sperm

A

Sperm doubles up, androgenesis 46XX

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5
Q

What is a hydatidiform mole a result of

A

Androgenetic –> complete moles usually due to homozygous 46XX.
Get proliferation of abnormal trophoblast issue
May get MALIGNANT trophoblastic tumour

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6
Q

What does parthenogenesis result in

A

Benign ovarian teratomas
Derived from oocyte after their first or second meiotic division
Diploid –> varying features, mostly epithelial tissues. Lacks skeletal muscle, placenta, membranes etc.

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7
Q

Why do parthenogenic embryos die

A

Failure of development of extra embryonic structures e.g. trophoblast

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8
Q

When do androgenic embryos dei

A

At the 6 somite stage, good extra-embryonic membranes developed but poor embryo development

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9
Q

What is genetic imprinting

A

Genes imprinted with a memory of the maternal/paternal origin –> ensures functional non-equivalence of the genes

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10
Q

How is genetic imprinting encoded

A

EPIGENETIC - not in the DNA
Due to modifications during gametogenesis
Affects the expression of 100-200 genes

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11
Q

What is Angelman Syndrome

A

Maternal deletion in chromosome 15

Causes ‘puppet children’ –> facially dysmorphic (smiling/laughing), mental handicap, seizures and ataxia/jerky movement

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12
Q

Main causes of Angolan Syndroe

A

Deletion in maternal chromosome 15 (75%)
Uniparental disomy (1%) - both paternal genes
Mutation (2-5%) –> in the UBE3A gene that is only expressed on the maternal genes –> inactivated in paternal genes

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13
Q

What is Prader-Willi Syndrome

A 
Infantile hypotonia
Hyperphagia --> causes obesity
Hypogenitalism in males, cryptochidism
Small hands/feet
Mental handicap
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14
Q

Causes of Prader-WIlli syndrome

A

Deletion in paternal genes
Deletion in chromsome 15 (75%)
Uniparental disomy (25%)

UBE3A mutation in paternal gene has no effect as paternal version is inactivated anyway

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15
Q

Are DNA Methyltransferases reversible or irreversible

A

Usually reversible

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16
Q

Where does DNA methylation occur

A

At CG diculeotides - which are involved in gene regulation

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17
Q

Where do CpG islands usually occur

A

Unmethylated clusters usually in the promoters of genes allowing transcription to occur

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18
Q

What happens if there is methylation in CpG islands in gene promoter regions

A

Silences the transcription of the gene

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19
Q

Do imprinted genes show mono allelic expression

A

Yes

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20
Q

What do paternal genes drive

A

Drive foetal growth, high foetal fitness and high foetal mortality

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21
Q

What do maternal genes drive

A

Restrain foetal growth, high mortality, poor long term reproductive potential but better maternal survival rate and reproductive fitness

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22
Q

What is Beckwithh Wireman Syndrome

A

Where the paternal drive of genes wins
High birth weight, organomegaly, tumour risk, hypoglycaemia, sporadic, epigenetic abnormalities

FOETAL OVERGRWOTH

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23
Q

What is Russell - Silver Syndrome

A

Maternal drive wins –> growth retardation

Persistent post natal growth failure, triangular face, assymetry

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24
Q

What chromosome abnormalities cause BWS and RSS

A

Abnormalities in chromosome 11p15.5!

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25
Q

What drives fetal growth

A

IGF2 –> normally expressed on the paternal side

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26
Q

What are the impacts of hypomethylation on chromosome 11

A

Decreases IGF2 –> causes RSS

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27
Q

What are the impacts of hypermethylation on chromosome 11

A

Increases IGF2 –> causes BWS

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28
Q

When does imprint switching occur

A

Must remember during somatic development
Forget at gametogenesis
New parental imprint is established –> essential for normal growth and development

29
Q

What chromosome is PGK1 on

A

X chromosome

30
Q

Why does X inactivation occur

A

Ensures male and females have equivalent doses of genes on chromosomes

31
Q

How does X-Inactivation occur

A

EPIGENETIC SILENCING

32
Q

Why is X-inactivation different to imprinting

A

Whole X-chromosome is silenced
Random choice of chromosome silenced
Occurs early in embryogenesis in the blastocyst –> get patches of cells with different X-chromsomes inactivated

33
Q

Why do you get tortoiseshell cats

A

Different X-inactivation in groups of cells

34
Q

What is hypohydriotic ectodermal dysplasia

A

Female carrier of X-linked mutation
Due to X-inactivation get patches of skin with/without sweat glands
Test with starch/iodine

35
Q

Are females epigenetic mosaics

A

Yes due to patches of cells with different X’s inactivated
Hence female carriers of X-linked mutations such as Haemophilis and Duchennes have some functional and some abnormal cells –> consequence is variable and unpredicatable

36
Q

What is pharamcokinetics

A

What the body does to a drug

37
Q

What is pharamcodynamics

A

what the drug does to the body

38
Q

what is stratified medicine

A

selecting therapies for groups of individuals with shared biological characteristics

39
Q

What is personalised medicine

A

therapies tailored to individuals

40
Q

Are SNPs usually functionally significant?

A

NO - but if proline produced causes kinks in protein which is bad

41
Q

What is the normal response rate to cancer drugs

A

Approx 20% due to genetic Varaition

42
Q

What does Thiopurine Methytransferase do? (TPMT)

A

Inactivates certain drugs –> mutations in it mean azothiprine (immunosuppressant) and 6-metacarptopirone and 6-thioguanine (chemo) aren’t inactivated hence you get toxic products

Mutation means higher drug toxicity as not inactivated

43
Q

Whos is TPMP 3A common in

A

White anglo saxons.

44
Q

Who is TMPT 3C common in

A

African americans

45
Q

What are n-acetyltransferases?

A

Liver enzymes that deactivate drugs by acetylation

Mutations mean you can get slow or fast acetylators!

46
Q

What drugs do n-acetyltransferases inactivate

A

Isonizaid (for TB)
Sulfasalazine (for Crohns)
Hydralazine (hypertension

47
Q

Who does fast acetylators arise in>

A

Nomadic populations with high meat eating diet

48
Q

What is succinylcholine

A

Muscle relaxant used in anaesthesia (stops breathing)

Related to curare in poison darts

49
Q

Mutation in what gene alters succinylcholine activity

A

Mutation in BCHE gene decreases bubrylcholinesterase activity
This enzyme normally deactivates succinylcholine
Hence mutation prolongs succinylchlines effects –> can lead to death if no ventilation

50
Q

What does mitochondrial MT-RNR1 gene encode

A

Encodes mitochrondiral 12s RNA

51
Q

What is amino glycoside induced hearing loss

A

G to A mutation, changes the mitochondrial rRNA structure to resemble E.Coli 165
Amino glycosides more likely to bind to this rRNA –> increases the risk of hearing loss at a younger age

52
Q

Is amino glycoside hearing loss maternally or paternally inherited?

A

Maternally as it is on mitochondrial RNA

53
Q

What mutations affect warfarin metabolism

A

VKORC1 and CYP2C9 mutations

54
Q

What do 20% of breast cancer overexpress

A

HER-2 (Human epidermal growth factors receptor 2)

55
Q

What can we treat HER-2 overexpression with

A

Trastozumav - a monoclonal antibody to HER-2

56
Q

What mutation is seen in 50% of melanomas

A 
BRAF mutation (BRAF is a serine protein kinase)
Valine to glutamic acid mutation
57
Q

What can we treat BRAF Mutation in melanoma with

A

Vemurafonib! But can have adverse effects in those without the mutation!

58
Q

What is Huntingtons Diesease

A

A progressive neurogenerative disorder
Affects movement
Depresses mood
Loss of cogntiion, function, memory loss

59
Q

When does huntingtons generally onset

A

35-44

60
Q

How is HUntingons inherited

A

Autosomal dominant - complete penetrance

HTT Gene on chromosome 4 –> contains a series of CAG nucleotide repeats

61
Q

What is Huntingtons caused by

A

An expansion of CAG nucleotide repeats on chromosome 4

62
Q

How many CAG nucleotide repeats is needed to cause Huntingtons

A

Over 40 usually

63
Q

What does CAG encode

A

Glutamic Acid

64
Q

How does CAG nucleotide repeats cause the huntingtons disease

A

Abnormal proteins with increased glutamic acid
Form PolyQ cellular protein aggregates
Basal ganglia affected especially caudate nucleus

65
Q

Are triplet repeat disorders associated with anticipation?

A

Yes –> they are unstable and prone to expand

66
Q

Which diseases in anticipation are linked to gender?

A 
Huntingtons - paternal 
Myotonic Dystrophy (AD) - maternal
Fragile X (XL recessive) - maternal means more likely to expand if you inherit it from the mmother
67
Q

What is the link between CAG nucleotide repeats and age of onset

A

Higher number of CAG nucleotide repeats causes lower age of onset
BUT applies to population as a whole but huge variation in individuals so can’t predict individually

68
Q

Do we offer testing on under 18s for Huntingtons

A

No - only prenatal and if positive then must have an abortion

69
Q

What is the treatment for Huntingtons

A

Symptomatic treatment only
No prevention or cure
Testing does NOT save lives but allows people to prepare

EMS - JL (10 decks)

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