Genetics Flashcards
What are the antenatal tests for down syndrome?
Screening: Combined screening (11-14 weeks) - foetal nuchal trnaslucency + HCG and PAPPA biomarkers Quadruple test (14-20 weeks) - beta-HCG, alpha fetoprotein, inhibin A and oestriol
Diagnostic:
Chronic villous sampling (1st trimester)
Amniocentesis (2nd trimester)
USS anomaly scan at 20 weeks
What is tested for in the guthrie screening test?
CF PKU Hypothyroidism Sickle cell anaemia MCADD MSUD (maple syrup urine disease) Galactosaemia
What is karyotyping used for?
Gross appearance of chromosomes - e.g. trisomies
What is Array CGH used for?
Sequences whole genome quickly –> comparative genomic hybridization
genomic abnormalities in cancer
Submicroscopic genetic aberrations (e.g. Pader Willi - Ch 15 imprinting)
Mosaicism
When is FISH used?
When the area of abnormality is already known e.g. looking for a deletion
What is a consanguineous marriage represented by in a pedigree?
double line
How would a pregnancy be represented on a pedigree?
diamond with ‘P’ in the middle
How would a carrier for an X-linked disorder be represented on a pedigree?
circle with dot in the middle
How is a miscarriage shown on a pedigree?
Diamond with a line pointing inwards at the bottom point
In a family affected by autosomal recessive what is the risk of unaffected children being carriers?
2/3
Common conditions for autosomal recessive?
CF Sickle Cell Thalassaemia PKU Congenital Adrenal Hyperplasia
Common autosomal dominant conditions?
Ehlers Danlos Anchondroplasia Marfan's syndrome Huntington's Mytonic dystrophy
Common X-linked disorders?
Duchenne’s
Fragile X
Colour blindness
Haemophilia A and B
What are the chances a daughter will be a carrier of an X-linked disorder if their father is affected?
100%
