Chromosomal Abnormalities Flashcards
Why are trisomies 21, 18, and 13 survivable whilst all other trisomies are lethal?
These chromosomes carry the least genetic information.
Why is Turnur’s monosomy survivable whilst all other monosomes are lethal?`
Because it is a monosomy of an X-chromosome, and having only one X-chromosome is survivable in males and is similar to Lyonization of X chromosomes in females.
Acrocentric chromosomes
(13, 14, 15, 21 and 22), centromere is located close to one end of the chromosome.
What is Philadelphia chromosome?
a somatic mutation via reciprocal translocation - causes ALL, CML.
When would you use karyotype?
When you need to see the whole genome/don’t have a specific hypothesis but suspect a chromosomal disorder. Suspect structural rearrangement such as Robertsonian translocation Downs Syndrome.
When would you use FISH?
To confirm a diagnosis based on a hypothesis formed via clinical presentation.
When would you use microarray?
When you suspect a copy number variant disorder (sections of the genome are repeated and the number of repeats in the genome varies between individuals in the human population) such as Williams syndrome.
What is Kleinfelter Syndrome and how does it arise?
Extra X chromosome (XXY), arises from nondisjunction in maternal meiosis, usually associated with advanced maternal age.
What is Turner’s Syndrome and how does is arise?
Monosomy - single X chromosome (have only 45 chromosomes as a result). Arises due to nondisjunction in meiosis of either parent, more likely with advanced maternal age.
The combination of growth retardation, multiple congenital abnormalities, and developmental retardation most strongly suggests:
Autosomal aneuploidy
