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Part 1 MRCOG > Genetics > Flashcards

Genetics Flashcards

1
Q

Lifetime risk of breast/ ovarian cancer with BRCA1 vs BRCA 2 gene

A

Breast: BRCA 1 50-65%, BRCA 2 40-55%

Ovarian: BRCA 1 40-65%, BRCA 2 15-25%

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2
Q

Human placental lactogen (HPL) structure

A

Polypeptide, 191 AAs. Similar to human growth hormone

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3
Q

Klinefelter’s syndrome

A

47 XXY
1:1000 live births
Features: tall, small testes with hypogonadotrophic hypogonadism, infertility

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4
Q

Types of blotting and what they detect

A

Northern- RNA
Southern- DNA sequence
Western- Protein

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5
Q

Mode of inheritance of BRCA genes

A

Autosomal dominant

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6
Q

Prevalence of Turner’s syndrome (45XO)

A

1 in 2500 live female births

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7
Q

Cell cycle stages and what happens in each

A

G1 (1st gap) –> S (Synthesis) –> G2 (2nd gap) –> M (mitosis) –> G1 (1st gap)

G1: Cell increases in size
S: Duplication of DNA
G2: Prepares for cell division
M: Mitosis

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8
Q

Introns vs exons

A

Exons = coding areas: code for protein that the gene encodes. Sequence is highly conserved between individuals

Introns = non-coding areas (longer than exons, not well conserved between individuals, spliced out during processing to mRNA)

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9
Q

DNA replication is…

A

Semi-conservative (every double helix in the new generation of an organism consists of one complete ‘old’ strand and one complete ‘new strand’

Bi-directional (one strand is 5’ to 3’ and the other is 3’ to 5’)

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10
Q

Base pairs DNA/ RNA

A

Pyrimidine-Purine

DNA:
Cytosine-Guanine
Adenosine-Thymine

RNA:
Cytosine-Guanine
Adenosine-Uracil

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11
Q

Karyotype of Turner syndrome

A

45XO

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12
Q

Lifetime risk of breast/ ovarian ca in general female population

A

Breast: 12%

Ovarian: 1.3%

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13
Q

Typical blood results for Down’s syndrome

A

Low PAPP-A
Low AFP
Low uE3
Elevated inhibin and beta hCG

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14
Q

Typical blood results for Edwards

A

Low PAPP-A
Low AFP
Low uE3
Low inhibin A
Low beta hCG

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15
Q

Combined test: what does it include and what is the wind to do it in?

A

PAPP-A, hCG and USS

11+2 to 14+1
NICE: 11+0 and 13+6

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16
Q

Triple test: what does it include?

A

AFP, hCG and uE3

17
Q

Quadruple test: what does it include and what is the wind to do it in?

A

AFP, hCG, inhibit A and uE3

14+2 to 20+0

18
Q

When should the mid-trimester anomaly scan take place?

A

18+0 to 20+6

19
Q

What percentage of inherited breast cancers are caused by BRCA gene mutations?

A

25%

20
Q

What percentage of people diagnosed with breast cancer will have a BRCA gene mutation?

A

5%

21
Q

Men with BRCA mutation are at increased risk of breast ca- what is their lifetime risk?

A

1-7%

22
Q

HNPCC: lifetime risk of colorectal and endometrial cancer

A

Colorectal: 78%
Endometrial 43%

23
Q

What percentage of Turner syndrome conceptions will miscarry?

A

95-99%

24
Q

Features of Turner syndrome

A

Clinically short stature, obesity, webbed neck, murmurs, ovarian failure (primary amenorrhoea), failure to develop secondary sexual characteristics

Raised FSH and LH (after age 10)

Thyroid dysfunction is common

25
Q

What are low vs high levels of AFP associated with in pregnancy

A

High: neural tube defects, anencephaly, multiple pregnancy, oesophageal and abdominal defects

Low: Down’s and Edward’s

26
Q

Inheritance pattern of beta thalassemia

A

Autosomal recessive

Homozygous b-thalassaemia (Major) produces severe transfusion dependent anaemia

Heterozygote b-thalassaemia produces mild microcytic anaemia

27
Q

Incidence of thalassaemia

A

1 in 100000 global incidence/ 70,000 babies born each year

28
Q

Gene mutation for beta thalassaemia

A

HBB gene chromosome 11

29
Q

Management of beta thalassaemia in pregnancy

A
  • Screen for diabetes
  • TFT screen
  • ECG and T2 cardiac MRI & cardiology review at 28 weeks
  • Biliary USS and ferriscan or liver T2
  • Offer bone density scan
  • Folic acid 5mg 3 months prior to conception
  • Major: should receive blood transfusions on a regular basis aiming for Hb >100
  • Offer early scan at 7-9 weeks
  • Serial growth scans 4 weekly from 24 weeks
30
Q

Thromboprophylaxis in pregnancy & beta thalassaemia

A

Women with thalassaemia who have undergone splenectomy and have a platelet count >600 should be offered LMWH & Aspirin (75 mg/day)

Women with thalassaemia who have undergone splenectomy or have a platelet count >600 should be commenced on Aspirin (75 mg/day)

Women with thalassaemia who are not already using prophylactic low-molecular-weight heparin should be advised to use it during antenatal hospital admissions

31
Q

What genetic mutation is Cri-du-Chat caused by?

A

Micro deletion of chromosome 5

32
Q

What are 90% of congenital adrenal hyperplasia cases caused by?

A

Abnormal CYP21A genes leading to 21 hydroxylase deficiency, resulting in androgen excess and mineralocorticoid deficiency

5% are due to 11 hydroxylase deficiency

33
Q

What is the leading cause of Down’s syndrome?

A

Nondisjunction maternal gamete

34
Q

What is the detection rate of Down syndrome using NT alone?

A

70%

35
Q

What percentage of miscarriages are thought to be attributed to Turner syndrome?

A

10-15%

36
Q

What percentage of first trimester miscarriages are due to trisomies?

A

68%

37
Q

HNPCC inheritance pattern

A

Autosomal dominant

38
Q

Kallman syndrome

Genetic inheritance/ gene mutation

A

A form of hypogonadotropic hypogonadism resulting from a lack of production of FSH and LH

Also experience lack of sense of smell

X linked recessive inheritance (no reported cases in females)
ANOS1 gene mutation

39
Q

Hb present in beta thalassaemia minor/ major

A

Minor: HbA (92-5%), Hb A2 (3-7%), HbF (1-5%)

Major: Higher percentages of HbF and HbA2 with absent or very low HbA

Part 1 MRCOG (13 decks)

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