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Y3 OBS AND GYNAE > Genetics > Flashcards

Flashcards in Genetics Deck (36)
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1
Q

How can placental tissue be obtained for genetic testing?

A

Chorionic villus biopsy from 11.5 weeks gestation

Testing with FISH or PCR for chromosome abnormality

2
Q

How can skin/urine cells of a foetus be obtained for genetic testing?

A

Amniocentesis from 16 weeks gestation

3
Q

How can blood of a foetus be obtained for genetic testing?

A

Foetal blood sampling from 18 weeks gestation

4
Q

How can foetal DNA be obtained for genetic testing?

A

Maternal serum from 8 weeks gestation

5
Q

Rank chorionic villus biopsy, amniocentesis, foetal blood sampling and maternal serum in order of greatest to smallest risk of miscarriage

A

Chorionic villus biopsy
Foetal blood sampling
Amniocentesis
Maternal serum (no risk)

6
Q

Rank chorionic villus biopsy, amniocentesis, foetal blood sampling and maternal serum in order of most viable to least viable tissue

A

Chorionic villus biopsy
Foetal blood sampling
Maternal serum
Amniocentesis

7
Q

What is confined placental mosaicism? Which method of genetic testing is it most associated with?

A

Discrepancy between chromosomal makeup of placental cells and cells in the baby
Chorionic villus biopsy

8
Q

List the indications for chromosomal analysis in pregnancy

A

Raised maternal age
Increased risk on screening: nuchal thickness, serum, DNA
Abnormality on ultrasound
Known parental abnormality

9
Q

What does array CGH analyse?

A

Changes in the number of copies of a particular gene in a diseased state
Basically looks at chromosome makeup

10
Q

List the 4 main genetic tests used for chromosome analysis and state whether these tests assess the whole genome or are targeted

A

Array CGH (whole genome)
Standard karyotype (whole genome)
FISH (targeted)
QF-PCR (targeted)

11
Q

What is the earliest stage of pregnancy where nuchal thickness can be assessed via ultrasound?

A

12 weeks

12
Q

List indications for obtaining free fetal DNA

A

Antenatal screening for down’s syndrome
Fetal sexing for X-linked disorders
Monogenic disorders

13
Q

Distinguish a mutation from a polymorphism

A

Genetic change that causes disease

Genetic variation that is not disease-causing

14
Q

List the most common types of chromosomal abnormalities

A

Aneuploidy (abnormal no. of chromosomes in a cell)
Rearrangements (translocations, inversions)
Deletions/ duplications

15
Q

List the main types of chromosomal translocations

A

Robertsonian (two acrocentric chromosomes end-end)
Balanced (all chromosome material present)
Unbalanced (extra or missing chromosome material)

16
Q

Which type of chromosomal translocation is the most common reproductive risk?

A

Unbalanced chromosomal translocation

17
Q

Large segments of unbalanced chromosomal translocation causes…

A

Miscarriage

18
Q

Small segments of unbalanced chromosomal translocation causes…

A

Dysmorphic delayed child

19
Q

What does pre-implantation genetic diagnosis (PGD) involve?

A

Perform a genetic test on an embryo before re-implanting it with “correct” genotype, using IVF

20
Q

What method is used to implant genetic info in PGD?

A

Intra-cytoplasmic sperm injection (ICSI)

21
Q

How old is the embryo when it is biopsied in PGD?

A

3 days

22
Q

List types of DNA analysis commonly used and their relative indication in pregnancy

A

aCGH for deletions/duplications in small sequences
Chromosome analysis for balanced rearrangements
NGS for large sequences
Non-invasive prenatal testing for large sequences

23
Q

What type of mutational change would produce an abnormal or absent protein?

A

Splice consensus altered

24
Q

What type of mutational change would make a short or absent protein?

A

Base change makes new stop

25
Q

What type of mutational change would make a different or non-functioning protein?

A

Base change alters amino acid sequence

26
Q

What is the main disadvantage of NGS in pre-natal testing?

A

It detects lots of polymorphisms

27
Q

When can fetal anomalies be identified during pregnancy on US scan?

A
Booking scan (10-12 weeks) 
Detailed scan (20 weeks)
28
Q

What is the pattern of inheritance for Duchenne muscular dystrophy?

A

X-linked recessive

Gene that can carry a DMD-causing mutation is on the X chromosome which passes from mother to son

29
Q

What is the risk of a child being affected by DMD?

A

1 in 4

1 in 2 if you know the child is male

30
Q

What is the risk of a child being affected by an autosomal dominant condition?

A

1 in 2 risk if parent is affected

31
Q

What is the risk of a child being affected by an autosomal recessive condition?

A

1 in 4 risk of affected child if parents are carriers

32
Q

What factors influence risk estimation of a child?

A
Family history
Obstetric history
Maternal history
Scan findings
Genetic tests
33
Q

What is the best genetic management if DNA testing in pregnancy indicates risk of inheritance?

A

Non-invasive fetal sexing

Chorionic villus biopsy if male

34
Q

List indications for consideration of PGD in pregnancy

A

Parental chromosomal abnormality (robertsonian translocation, reciprocal translocation)
X-linked disorders (reimplantation of female embryo)
Other single gene disorders (spinal muscular atrophy, cystic fibrosis, huntingdon’s disease)

35
Q

What is a Robertsonian translocation?

A

Chromosomes break at their centromeres and the long arms fuse to form a single, large chromosome with a single centromere

36
Q

What is a reciprocal translocation?

A

Chromosome abnormality caused by rearrangement of parts between non-homologous chromosomes