12. Karyotyping Flashcards

Trisomy 21

Trisomy 18

Trisomy 13

Turner’s Syndrome

Fanconi’s Anaemia
reciprocal translocation
segments from two different chromosomes have been exchanged
Robertsonian translocation
an entire chromosome has attached to another at the centromere; (only chromosomes 13, 14, 15, 21 and 22).
Rings
a portion of a chromosome has broken off and formed a circle or ring
Isochromosome
a mirror image copy of a chromosome segment including the centromere
Interstitial deletion
DNA lost from middle of chromosome
Terminal deletion
DNA lost from end of chromosome

Cri du chat syndrome
Severe mental development problems
small head
unusual facial features
Fanconi’s Anaemia
Increased pigmentation
Bone marrow failure
Increased risk of neoplasia
Numerical sex chromosome abnormalities
Minimal effect on survival of foetus
Balanced translocations
Usually no phenotypic effect
Unbalanced autosomal translocations
Multiple congenital malformations
Polyploidy
Commonly caused by fertilisation of the same egg by two or more sperm

Mitosis

Meiosis
Non-dysjunction
Failure of separation of homologous chromosome pairs
Both pairs migrate together to one pole
Autosomal trisomies - most common outcome
Trisomy 13
Patau’s
Trisomy 18
Edward’s

Patau’s
Severe mental development problems
Cardiac abnormalities
Cleft lip
Polydactyly

Edward’s
cardiac and renal defects
Club foot / rocker bottom feet
Small low set ears
Tightly clenched hand

Turner’s Syndrome
short stature
neck webbing
Cardiovascular abnormalities

Klinefelter Syndrome
Hypogonadism
Gynaecomastia