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EMS - JL > 9, 10, 11 > Flashcards

9, 10, 11 Flashcards

1
Q

What stain do you add in G banding

A

Trypsin - Leishmann Stain

AT regions go dark, GC regions are light

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2
Q

How long does G banding take

A

30 mins to 4 hours

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3
Q

How long does FISH take

A

10 mins to 1 hour

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4
Q

When do you denature DNA in FISH

A

In metaphase or interphase

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5
Q

What are 3 types of FISH probe and what do you use them for

A

1) Unique sequence
2) Centromere - shows aneuploidies
3) Paint - shows translocations

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6
Q

What % of the human genome is CNV

A

12%

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7
Q

High copy number of CCL31 causes

A

decreased susceptibility to HIV

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8
Q

Low copy number variation of FGGR3B

A

increases susceptibility to inflammatory autoimmune diseases

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9
Q

What does an MLPA do?

A

Can look at copy number variations in upto 50 genomic imbalances at a time

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10
Q

Describe MLPA Process

A

50 different probes each with different stuffer sequence attached, add to DNA and hybridise, ligation reaction to join 2 halves of probes by thermostable ligase, PCR amplification using single piemr pair, analyse area under peaks

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11
Q

Is Microarry CGH genome wide

A

Yes
It shows genomic imbalances (copy number variations)
High detection rates and high resolution

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12
Q

How much blood do you need for a microarry CGH

A

3ml in EDTA

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13
Q

Who do we test with microarrays

A

those with learning disability and dysmorphic infacnts

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14
Q

How big must the imbalance be to detect on microarray CGH

A

Over 150kb

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15
Q

What are the disadvantages of micro arrays

A

Only measures dosage changes, not balanced rearrangements or mutations
doesn’t detect low levels mosaicism
Needs good quality DNA
non-pathogenic and uncertain pathogenic changes also detected

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16
Q

What is QF-PCR

A

PCR amplification of short tandem repeats using fluorescent probes. Products visualised and quantified

the short tandem repeats are chromosome specific

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17
Q

What does each box in a micro satellite tetra nucleotide repeat marker show?

A

Each box who’s a tetra nucleotide repeat. compare maternal and paternal values

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18
Q

What is qPCR used for?

A

Quantitive comparison to reference gene. Confirms small CNVs when FISH is unsuitable

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19
Q

How much blood do we need for G banding

A

2-5ml, stimulate T lymphocytes, culture 2-3 days and then G band analysis performed

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20
Q

Recurrence risk of Free Trisomy 21

A

95%

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21
Q

Recurrence risk of Mosaicism Trisomy 21

A

If occurred post zygotic = minimal (47xx +21/46XX)

If occurred in meiosis = 1% (47X +21)

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22
Q

Recurrence risk of 46XX der(21:21)

A

100% as 2 chromosome 21 stuck together

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23
Q

Recurrence risk of 46XX der (14:21)

A

Male carrier = 2% as trisomy 21 sperm less viable

Female carrier = 12%

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24
Q

What do we use to clarify imbalnces

A

FISH

25
Q

Recurrent miscarriages often due to:

A

2-3% due to balanced chromosome change

26
Q

what % of males infertile due to chromosome changes

A

10%

27
Q

What chromosomes are prone to translocatinos

A

4 & 11
In meiotic pairing you get Pachytene Cross (quadrivalent forming) - also occurs in trisomy 21 roberstsonian translocation. Alternate controllers in the chain move to the same pole

28
Q

What is Wolff Heschung condition

A

Loss of 4p chromosome

29
Q

What is NIPT

A

Non-inasive Prenatal Testing. Take maternal blood, extract free circulating metal DNA. Assess aneuploidyies of 13,18,21 if high risk do invasive test

30
Q

What indicates prenatal diagnosis

A

Increased maternal age, serum screen risk, abnormal USS, Family history/previous chromosome abnormality

31
Q

Signs of downs syndrome

A

Serum test - low alphaFP, low estriol, high hCG
Nuchal thickness of 6mm
High maternal age

32
Q

What causes 50% of spontaneous abortions

A

chromosome abnormalities

33
Q

What type of abnormality links most cytogenetics and cacner

A

Translocations

34
Q

What is MYGN gene amplification associated with

A

Neuroblastoma

Has poor prognosis, give high dose chemo

35
Q

CML Translocation

A

between chr 9 abl gene and chr 22 bcr gene.

Creates bcr/abl fusion gene –> FISH cTan detect this
bcr/abl gives a Rh +ve interphase

36
Q

What type of inheritance is Cockaynes syndrome

A

Autosomal recessive
Delays growth, causes premature ageing, degenerative condition, ataxia, photosensitivity and impaired development of the nervous system

Usually only live till about 7.

37
Q

What does CK test for

A

Tests for muscular dystrophy

38
Q

aCGH shows what?

A

Imbalances at chromosome level

Shoes copy number variations that can account for learning/behavioural/congenital phenotypes

39
Q

Mutations are responsible for how much familial cancers?

A

16% in the under 35s

40
Q

BRCA1/2 risk of breast and ovarian cancer

A

85% by 70 years for breast

55% for ovary BRCA1, and 25% for ovary for BRCA2

41
Q

Treatments of BRCA

A

Remove ovaries (reduce risk by 85%), preventative mastectomy (reduces risk by 90%)
Specific treatments such as cisplatin and PARP inhibitors
Tamoxifen, diet and exercise also to reduce risk

42
Q

What chromosome are the BRCA genes on

A

17

43
Q

What is Treacher-Collins Syndrome

A

Problem in the migration of neural crest cells to the front of the face
Get small chin/narrow constricted airways
Can do prenatal screening (assess the need for a tracheostomy)

44
Q

What week can you do a NGS of mothers blood

A

aka NIPT at about 10 weeks

45
Q

What does leptin do?

A

decreases food intake, increase thermogenesis, increases physical activity and increase metabolic rate

THIS ALL CAUSES FAT CELL MASS TO DROP

46
Q

What produces leptin

A

fat cells

47
Q

What happens if you are leptin defecient

A

You can become obese –> use leptin replacement therapy

48
Q

What is classical gene therapy

A

introduce functional genes/DNA to replace the mutated

49
Q

What is newer gene technology

A

Repairs the mutated genes

50
Q

What is Lebers Congenital Amaurosis

A

Rare inherited recessive eye disorder. Involved 22 genes. Causes 10-18% of congenital blindness

51
Q

Why is Lebers Congenital Amaurosis a good target for gene therapy

A

as the eye is immune privileged (unlikely to mount an immune response), accessible for injection

Do sub retinal injections with aden-associated viruses containing human RPE65 and human RPE65 promoter
BUT need a structurally normal retina, only works with missions mutations and only a single gene with loss of function
Ambylopia may inhibit result so best to do in children

52
Q

What mutation is seen in Lebers Congenital Amaurosis

A

Mutation in RPE65 (retinal pigment epihtelium)

It is involved in transduction recycling isomerase so it can capture light again

53
Q

What vitamin is needed to capture light

A

Vitamin A

54
Q

What are cytochrome P450 oxidases

A

Multilane family predominantly in the liver, responsible for the metabolic elimination of most drugs and the activation of pro-drugs to their active form

55
Q

What cytochrome P450 metablises most drugs

A

CYP2D6

56
Q

What % of caucasians are non-metabolites with no CYP2D6 activity and what % are ultra-rapid metabolites with multiple copies of CYP2D6

A

non-metabolites - 6/10%

ultra-metabolites - 7%

57
Q

What is the rate limiting step in converting tamoxifen into its active form of endoxifen

A

CYP2D6

HENCE if poor CYP2D6 function then tamoxifen is not converted to its active form and is of no use

58
Q

When do we give tamoxifen

A

give after a mastectomy to prevent prevent breast cancer

EMS - JL (10 decks)

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