Antenatal Genetics

Question 1

what is a gene mutation?

Answer 1

a change in the nucleotide sequence in a particular gene (e.g. CF deltaF508)

Question 2

What is a chromosome mutation?

Answer 2

An alteration of the nucleotide sequence of a segment of a chromosome, which includes many genes (e.g. down’s trisomy 21)

Question 3

guy doesn’t know if he has Huntingtons (AD), His father had Huntington’s disease. He wants to have a kid, whats the risk the kid will get it?

Answer 3

25%

Son has to inherit (50% chance) then son has to give it to baby (further 50% chance).

So 0.5 X 0.5 = 0.25

Question 4

Claire is a carrier of CFTR gene mutation (autosomal recessive). Her brother has CF, she does not. What is the likelihood of her child being affected (her husband is an individual of European descent)?

Answer 4

1/72

She doesn’t have CF so she may only be a carrier or not a carrier (+I, I+, II) she has a 2/3 chance of passing the mutation to her child.

The husband has no Hx of CF but is of European descent so has risk of 1/24.

So
2/3 X 1/24 = 1/72

Question 5

what is PGD and is it legal?

Answer 5

Preimplantation genetic diagnosis

legal in UK, only justified when used to determine against passing on serious inherited disease (authorised by HFEA)

Question 6

When can PGD be considered?

Answer 6

• Parental chromosome abnormality (Robertsonian/reciprocal translocation)
• X-linked disorders (re-implantation of female embryos)
• Other single gene disorders (e.g. Spinal muscular atrophy, CF, Huntington’s)

Question 7

used to analyse chromsomal deletions/duplications

Answer 7

aCGH

Question 8

example of next generation sequencing…

Answer 8

NIPT (non-invasive prenatal testing)

Question 9

How to gain some insight as to what to look for in NIPT?

Answer 9

US
FHx
Pregnancy Hx

Question 10

If X linked disease what should be management steps?

Answer 10

Test for sex (non invasive maternal serum test)

If male then do CVB