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Genetics Flashcards

1
Q

Describe Prader-Willis syndrome

A

Loss of function of the paternal chromosome

Critical region is deleted OR 2 maternal copies are inherited (uniparental isodomy)

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2
Q

What are the symptoms of Prader-Willis syndrome

A 
Hyperphagia (overeating with loss of regulatory process)
Obesity
Mental retardation
Hypotonia (reduced muscle tension)
short
Infertile
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3
Q

Describe Angelman syndrome

A

Loss of function of the maternal chromosome

Imprinting defects OR UB3A mutations

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4
Q

How is Prader-Willis syndrome treated

A

Diet restriction
Exercise for muscle
Growth hormones
Hormone replacement

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5
Q

What is the karyotype of the mitochondria

A

36 genes

2-10 copies are circular genomes

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6
Q

Describe MELAS

A

Mitochondrial myopathy Encephalopathy Lactic Acidosis and Stroke
Progressive neurodegenerative disorder
The muscle and brain have lots of mitochondria so they are heavily affected

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7
Q

What are the symptoms of MELAS

A

muscle weakness
episodic seizures
stroke-like episodes
vomiting

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8
Q

Describe LHON and what are the symptoms

A 
Leber's hereditary Optic Neuropathy
More common in males 
Bilateral vision (loss of central vision)
Optic atrophy
Blindness
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9
Q

Describe PKU and its symptoms and treatment

A 
Phenylketonuria 
Deficiency of phenyladenine hydroxylase 
Severe retardation
Eczema
Blonde hair and blue eyes
Reduced melanin
Remove phenylalanine from the diet
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10
Q

Describe MCAD deficiency and its treatment

A

Medium chain Acyl coA dehydrogenase deficiency
Common disorder of fatty acid oxidation
Sudden death
Beta oxidation cannot occur so fasting an hypoglycaemia is dangerous
adjust caloric intake and avoid fasting

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11
Q

Give examples of types of mutations

A 
Aneuploidy
Translocation
chromosome:
Macro-deletions
Macro-insertions
gene:
Large insertion
Large or deletions

Point mutation

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12
Q

What are the hallmarks of cancer

A 
Dysregulated growth
Evasion of apoptosis
Limitless replication
Sustained angiogenesis
Invasion/ metastasis
Genome instability and mutation (disordered growth, disordered death, disordered behaviour)
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13
Q

Explain what a polyclonal disease is

A

Cancer is polyclonal

Many clones of varied genetically distinct cells

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14
Q

Compare driver to passenger mutation

A

driver - The 1st key mutation
Can cause a normal cell to become a cancer cell

passenger - mutations that don’t contribute to the development of cancer but have occurred during cancer growth

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15
Q

What percentage of breast cancers are caused by germline mutation and of what genes

A

2.4%
BRCA1 or BRCA2
BRCA2 predisposes to breast cancer in men

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16
Q

Describe breast cancer as mutations

A

Hit 1 is inherited
hit 2 may not always occur
BRCA genes are TS genes that repair DNA by homologous recombination which cannot happen with mutation

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17
Q

Which defects in cell division or DNA repair influence the risk of familial colorectal cancer

A

Familial adenomatous polyposis

Lynch syndrome

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18
Q

Describe familial adenomatous polyposis

A

Thousands of intestinal polyps which contribute risk to colorectal cancer
Caused by the APC gene on chromosome 6
Autosomal dominant

19
Q

Describe HNPCC

A

hereditary non polyposis colorectal cancer
Most common inherited form
mutation of MLH1 or MSH2 (DNA repair genes)

20
Q

Describe oncogenes and tumour suppressors

A

Proto-oncogenes promote growth and proliferation in cells and those that are in overdrive are oncogenes.
Signalling cascades and mitogenic pathway activation

TS genes regulate cell division, DNA damage, apoptosis and DNA repair
mutations cause loss of function and faulty cell division

21
Q

Describe chronic myeloid leukaemia

A

Clonal myeloproliferative disorder => overproduction of mature granulocytes
Middle ages/elderly
3 phases: chronic (benign), accelerated (omnious), blast crisis (acute leukaemic, invariably fatal)
Philadelphia chromosome is found in >90% produces a new tyrosine kinase

22
Q

What are the indications of testing

A 
Nuchal scan
Mid-trimester
Previous pregnancies with DS or CF
Parents are carriers of chromosome rearrangement or genetic condition
FH of genetic condition
23
Q

Describe the nuchal scan

A

Looks at the thickness of the fluid at the back of the fetal neck
> 3mm indicates a chromosomal abnormality
Not a diagnostic test
Could be Down’s, Edwards, Patau or cardiac

24
Q

What is the combined test for Down’s

A

Combined test =levels of the hormone free beta-hCG +protein PAPP-A
High hCG and Low levels of PAPP-A.

25
Q

Describe the mid-trimester scan

A

20 weeks
dates the pregnancy
Diagnose miscarriage or fatal anomalies

26
Q

What are the reproductive options available

A

Planning prenatal testing
Facilitating decision making
Seeing patients in clinic following diagnosis in utero
Arrange termination if necessary
Discuss recurrence risks and plans for future pregnancies
Taking into account: previous experiences, family situation, personal beliefs, psychosocial situation, miscarriage risk with genetic risk

27
Q

What types of scanning are done in pre-natal testing

A

ultrasound - early scan, nuchal, anomalies in hands, feet, face, lip
MRI at 20 weeks

28
Q

Describe non-invasive pre-natal testing

A

Maternal serum screening = testing serum markers in the blood for trisomy 21 or 18 + nuchal measurement
cell-free fetal DNA = analysing DNA fragments in the maternal plasma during pregnancy. baby at 9 weeks. Only 10-20% from the placenta
ultrasound

29
Q

What are the disadvantages of non-invasive testing

A

Both not as useful for multiple pregnancies

non-invasive is harder with a greater BMI

30
Q

Describe Amniocentesis

A

Invasive
16 weeks onwards
Sample the amniotic fluid which contains fetal cells
1% miscarriage risk, infection, Rh sensitisation

31
Q

Define heritability

A

The study of genetic contribution to increased risk of disease
Studies usually use mono and dizygotic twins

32
Q

What is the copy number variant

A

Repeated code
Deletions, duplications, insertions that increase polygenic disease risk
Found in obeisty

33
Q

What are the types of obesity

A

Monogenic - dominant or recessive single gene disorder
Common - general population
Syndromic - e.g. Prader Willis

34
Q

What is leptin

A

Hormone made by adipocytes inwards white adipose tissue which circulates in proportion to the amount of adipose tissue
Inhibits appetite via the hypothalamus
High with high fat

35
Q

What are the symptoms of monogenic leptin deficiency

A 
hunger
obesity
no puberty
poor growth
Low thyroid
36
Q

Give examples of genes that cause single gene obesity

A 
MC4R = dominant 
PCSK1 = recessive
POMC = recessive
MRAP2 = recessive
37
Q

How is obesity clinically management

A

Lifelong prevention
Lifestyle measures
Medication
bariatric (weight loss) surgery

38
Q

How is obesity diagnosed

A

PCR for diagnosis
Pre-implantation diagnosis for IVF embryos
Mitochondrial transfer (3 parent babies)

39
Q

What is Sanger sequencing

A

Amplifying the region of interest with nucleoside terminators
Genetic sequence of the region of interest

40
Q

What is Next generation sequence

A

Fragmentation, sequencing and mapping of reads

sequence of the genome/transcriptome

41
Q

What are the advantages and disadvantages of Sanger sequencing

A

quick
gives sequence

cannot multiplex
Limited to 2000bp

42
Q

What are the advantages and disadvantages of next generations sequencing

A

Massively multiplex
Multiple different libraries

Cost
Time
Read-depth
Data overload
Library bias
43
Q

Describe chorionic villus sampling

A 
Invasive
11-14 weeks
1-2% miscarriage risk
Sample of chorionic villi part of developing placenta (same DNA as the foetus)
Ealier result than amniocentesis

?? (14 decks)

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