A/51 Flashcards
Types of abnormalities that cause cytogenic disorders (2)
- numerical abnormalities
- structural abnormalities
Types of numeric abnormalities (4)
- Euploid
- Polyploidy
- Aneuploidy
- Mosaicism
What usually causes aneuploidy?
non disjunction of a homologous pair of chromosomes
Types of structural abnormalities (4)
- Translocation
- Isochromosomes
- Deletion
- Inversions
What is a robertsonian translocation
Break occurs at the centromere of an acrocentric chromosome, creating one long chromosome and one short chromosome
What is an isochromosome?
centromere divides horizontally, not vertically, so the final chromosome is made of the 2 long arms / 2 short arms
Which has the worst affect? absence / excess?
Absence : deletion, monosomy in autosomal (not sex) chromosomes
Prevalence of trisomy 21
1/700 births
What has a strong influence on the prevalence of trisomy 21?
Maternal age : over the age of 45, 1/25 births are affected
5 autosomal abnormalities
- Trisomy 21
- Trisomy 18 - edwards
- Trisomy 13 - patau
- Cri du chat syndrome
- 22q11.2 deletion syndrome - digeorge
Prevalence of trisomy 18
1 / 8.000 births
5 anatomical characteristics of Trisomy 18 / edwards syndrome
- mental retardation
- congenital heart defects
- renal malformation
- overlapping fingers
- short neck
Prevalence of trisomy 13
1 / 15.000 births
5 anatomical characteristics of trisomy 13 / patau syndrome
- polydactyly
- microcephaly
- mental retardation
- cleft lip / palate
- heart defects
What is cri du chat syndrome?
deletion of short arm of chromosome 5
