Genetics Flashcards
list the genetic tests in order of the size of mutations it can find from biggest to smallest
chromosome analysis
aCGH - for deletions/ duplications
PCR and sanger sequencing
next generation sequencing
what does aCGH look for
chromosome deletions/ duplications- analysis for UNBALANCED rearrangements
how does splice consensus alterations or a base change making a new stop affect translation
altered mRNA leading to decay and short/ abnormal or absent protein made
how does a base change affecting amino acid order affect translation
different or non functioning protein made
when is a booking USS done
10-12 weeks
when is a detailed USS scan done
20 weeks
what specific abnormalities are looked for on USS
Cardiac (12-20 weeks)
Microcephaly (Usually after 22 weeks)
Short Limbs (Usually after 22 weeks)
Brain malformations
what is the chance of a child being affected by an x linked disease when the mother is a carrier
1 in 4 for females
1 in 2 for males
what is the risk of a child be affected by an AD condition if one parent affected
50%
are males or females more likely to be affected by AD conditions
affected equally
what are the risk of a child being affected by an AR condition if both parents carriers
1 in 4
what genetic conditions pose a threat to maternal health in pregnancy
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)
what DNA testing is done in pregnancy
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
what is the best tests to do for genetics in pregnancy with FHx of duchennes
non invasive fetal sexing (USS)
chorionic villus biopsy if male
what is pre implantation genetic diagnosis
when genetic tests done of embryo before re implanting one with the ‘correct’ genotype
what are the options for people at risk of a pregnancy with a genetic disorder
Have no further children Take a chance Prenatal testing Gamete donation Adoption Preimplantation diagnosis
how is preimplanation sex determination done
using FISH- different coloured probes to label chromosomes X, y and 18 (18 for a control)
what are the downsides of pre implantation diagnosis
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)
what are the advantages of pre implantation genetic diagnosis
pregnancy less likely to be affected from the onset
reduce the need for TOP
when might preimplantation genetic diagnosis be done
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
when do you need to refer to a clinical geneticist
when FHx of disease that may affect pregnancy (fetus or mother)
unexpected findings on genetic testing/ USS
when a previous pregnancy/ child has malformations
does aCGH see an unbalanced mutation
yes
when is antenatal testing for huntingtons done
only when parents sure of TOP if test +ve
what is uniparental disomy
where gametes gets two chromosomes from one parent
