Chromosomal Abnormalities Flashcards
What is a human karyotype?
A picture of a cell’s complete set of chromosomes grouped together in pairs and arranged in order of decreasing size
How is it obtained?
Process involving Venous blood / Amniotic cells and CVS.
Use white cells, stop during metaphase (Commonly now prophase)
Use stain and place on slide
Ideogram
Show structural feature
p-arm? short or long
Short (petite)
What does 47, XX +21
47 total number of chromosome, XX denotes the sex of the individual, +21 . Means the extra chromosome is chromosome 21.
Heterochromatin (dark) on ideogram
More compact (fewer genes)
Euchromatin (light) on ideogram
More open (more genes)
What is non-disjuncture?
Result in uneven number of chromosomes occurs during meiosis.
Causes Trisomy and monosomy
What is the most common aneuploidy? Why is there tolerance?
Sex chromosomes tolerance as often X inactivation in females and y gene in males are in a low content.
When can sex aneuploidy become a problem?
pseudoautosomal region. i.e. even when some genes remain active even if the chromosome is inactivated.
What are the three abnormalities of chromosome structure?
Numerical
Structural
Mosaicism
What are Single chromosome abnormalities?
Inversion of a gene, duplication and deletion of a gene
What are two chromosome abnormalities?
Translocation
What is mosaicism?
Presence of two or more populations of cells with different genotypes. Mild phenotype
What are numerical abnormalities and why is caused?
Monsomy,
Trisomy
Non-dysjunction
What are the structural abnormalities?
Insertion, Duplication, Inversion, Translocation Robertsonian translocation
