Genetics: From Whole Chromosomes to Single Bases Flashcards
how is a chromosome recognised
- centromere position
- length
- banding patters with specific stains
what is the make up of a chromosome
- telomeres at either end
- centromere
- short arm (p)
- long arm (q)
what are acrocentric chromosomes and what are they liable to
- chromosomes that can lose their short arm without consequences for that individual
- translocations
aneuploidy
whole extra/missing chromosome
balanced translocation/re-arrangement
all genetic material is present
unbalanced translocation/re-arrangement
genetic material is missing or extra (1/3 copies)
what is a robertsonian translocation and what does it pose a risk of
- two acrocentric chromosomes stuck end-to-end, translocation
- risk of trisomy in offspring
why is X-chromosome aneuploidy better tolerated
X-chromosome inactivation
what do unbalanced translocations result in in pregnancy
- miscarriage
- dysmorphic delayed child
FISH
fluoresent in-situ hybridisation
what does FISH detect
chromosomal abnormalities
how does FISH work
- maps all the genetic material in a cell and targets a specific sequence
- flurescent markers are attached to this sequence and you are now able to see if its present
what does an aCGH detect
detects deletions/duplications - any size imabalance but not balanced translocations
how do an aCGH work
takes the entire genome and compares it to a reference sample
what indicates deletions in aCGH
half as much DNA on the graph compared to reference
