Errors in meiosis and X inactivation Flashcards
What is down syndrome classified as genetically?
A trisomy - having an additional chromosome
What is wrong genetically with those which downs syndrome?
They have 3 copies of chromosome 21 instead of two copies (suposed to have one from mum and one from dad)
What is a aneuploidy?
The presents of an abnormal amount of chromosomes in a cell
How does the trisomy in down syndrome occur?
From disjunction, when the chromosomes don’t separate properly.
- Failure of chromosomes to seperate properly during meiosis
- Happens in meiosis 1 and 2
What is Klinefelter syndrome?
Being XXY in sex chromosomes (human aneuploid)
- These individuals are male
- Mildly impaired iq, slightly female physique, tall
What is turner syndrome?
- Only one sex chromosome (XO)
Female, short neck fold
What is polyploidy?
The possession of multiple sets of chromosomes
What happens genetically in a polyploid?
Chromosomes don’t pair up properly during meiosis as they are not exact homologs of each other, so they double to make an exact homologous pair. This means the chromosome number will double.
What is a chromosomal deletion?
A deletion removes a chromosomal segment
What is a chromosomal inversion?
An inversion reverses a segment within a chromosome
What is a chromosomal duplication?
A duplication repeats a segment
What is a chromosomal translocation?
Moves a segment from one chromosome to a nonhomologus chromosome
What is Lejeune syndrome?
Deletion of tip of short arm of chromosome 5
Individuals are intellectually disabled, and usually die in childhood
