Chromosomal disorders Flashcards
What is a human karyotype?
A gross screen performed on dividing cells to detect major changes in chromosomes but will not pick up on point mutations or small deletions
What is the difference between a telomere and a centromere?
Telomere is the end of the chromosome and centromere is the centre
What are the p and q arms?
P arm is short and q arm is long
What is aneuploidy and its varieties?
Aneuploidy is the gain or loss of a whole chromosome
Loss of one is monosomy
and gain of one is trisomy
Occurs during non disjunction of meiosis
What is mosaicism?
If non disjunction occurs post zygotically, you can end up with different cells with different numbers of chromosomes in them within the same person
Describe reciprocal translocation
An exchange of material between two chromosomes. Can be balanced (phenotypically normal) or unbalanced (carriers can have lots of miscarriages/oligospermia)
Describe Robertsonion translocation
Carrier has 45 chromosomes as two have combined but is phenotypically normal
Describe inversion of a chromosome
Two breaks in the same chromosome
Can involve both chromosome arms (pericentric) or only one arm (paracentric)
Usually phenotypically normal
What are the two types of deletion?
Terminal- loss of an end fragment
Interstitial- loss of a bit in the middle
What are target DNA and probe DNA in terms of FISH?
Target DNA: the tissue that has been immobilized on the slide
Probe DNA: a piece of DNA of known composition- labelled with fluorochrome
What is FISH useful for?
Detection of smaller individual mutations present in cancer and congenital disorders (gene amplification/rearrangements)
What is comparative genomic hybridisation? (CGH)
Normal and target DNA are compared by scanning the entire genome for DNA changes
