Genetics

Question 1

list the genetic tests in order of the size of mutations it can find from biggest to smallest

Answer 1

chromosome analysis
aCGH - for deletions/ duplications
PCR and sanger sequencing
next generation sequencing

Question 2

what does aCGH look for

Answer 2

chromosome deletions/ duplications- analysis for UNBALANCED rearrangements

Question 3

how does splice consensus alterations or a base change making a new stop affect translation

Answer 3

altered mRNA leading to decay and short/ abnormal or absent protein made

Question 4

how does a base change affecting amino acid order affect translation

Answer 4

different or non functioning protein made

Question 5

when is a booking USS done

Answer 5

10-12 weeks

Question 6

when is a detailed USS scan done

Answer 6

20 weeks

Question 7

what specific abnormalities are looked for on USS

Answer 7

Cardiac (12-20 weeks)
Microcephaly (Usually after 22 weeks)
Short Limbs (Usually after 22 weeks)
Brain malformations

Question 8

what is the chance of a child being affected by an x linked disease when the mother is a carrier

Answer 8

1 in 4 for females

1 in 2 for males

Question 9

what is the risk of a child be affected by an AD condition if one parent affected

Answer 9

50%

Question 10

are males or females more likely to be affected by AD conditions

Answer 10

affected equally

Question 11

what are the risk of a child being affected by an AR condition if both parents carriers

Answer 11

1 in 4

Question 12

what genetic conditions pose a threat to maternal health in pregnancy

Answer 12

Myotonic Dystrophy
Haemophilia A or B (bleeding disorders)
Hereditary Haemorrhagic Telangiectasia (abnormal blood vessel formation in the skin, mucous membranes, and organs including the lungs, liver, and central nervous system)

Question 13

what DNA testing is done in pregnancy

Answer 13

Usually PCR based
Results in 2-3 days

Occasionally southern blotting
May take 2-3 weeks

Chorionic Villus Biopsy at 11.5+ weeks
Amniocentesis at 16+ weeks

Question 14

what is the best tests to do for genetics in pregnancy with FHx of duchennes

Answer 14

non invasive fetal sexing (USS)

chorionic villus biopsy if male

Question 15

what is pre implantation genetic diagnosis

Answer 15

when genetic tests done of embryo before re implanting one with the ‘correct’ genotype

Question 16

what are the options for people at risk of a pregnancy with a genetic disorder

Answer 16

Have no further children
Take a chance
Prenatal testing
Gamete donation
Adoption
Preimplantation diagnosis

Question 17

how is preimplanation sex determination done

Answer 17

using FISH- different coloured probes to label chromosomes X, y and 18 (18 for a control)

Question 18

what are the downsides of pre implantation diagnosis

Answer 18

Requires IVF (Expensive, Invasive)

Overall 30% take home baby rate per cycle (Emotional rollercoaster)

DNA analysis less reliable than prenatal testing (Analysis of a single cell)

Multiple pregnancy risk (IVF procedure)

Question 19

what are the advantages of pre implantation genetic diagnosis

Answer 19

pregnancy less likely to be affected from the onset

reduce the need for TOP

Question 20

when might preimplantation genetic diagnosis be done

Answer 20

Parental chromosome abnormality:

• Robertsonian translocation
• Reciprocal translocation

X-linked disorders
-re-implantation of female embryos

Other single gene disorders

• Increasing numbers of conditions
• Spinal Muscular Atrophy
• Cystic fibrosis
• Huntingtons disease

Question 21

when do you need to refer to a clinical geneticist

Answer 21

when FHx of disease that may affect pregnancy (fetus or mother)
unexpected findings on genetic testing/ USS
when a previous pregnancy/ child has malformations

Question 22

does aCGH see an unbalanced mutation

Answer 22

yes

Question 23

when is antenatal testing for huntingtons done

Answer 23

only when parents sure of TOP if test +ve

Question 24

what is uniparental disomy

Answer 24

where gametes gets two chromosomes from one parent