Clinical cytogenetics Flashcards
What are 7 reasons why someone might be sent for cytogenetic analysis?
- Early growth and development delays
- Stillbirth or neonatal
- Cognitive impairment or facial dysmorphism
- Persistent fertility issues
- Family history
- Neoplasia
- Pregnancies in women of advanced age
Why would someone be sent for cytogenetic analysis if they have persistent fertility issues?
They might be a translocation heterozygote
What is FISH?
Fluorescent in situ hybridization
When during the cell cycle can FISH be used?
Either interphase or metaphase. Metaphase needs a few extra steps but is better for seeing translocations. Interphase is good when looking for the presence or absence of a sequence
What are the probes used in FISH?
Fluorescently labelled single stranded nucleic acids complementary to the sequence of interest
What sort of probe would we use if we were looking for a particular locus, region, or chromosome?
One that binds to the sequence of interest and only the sequence of interest
Why would we use a probe for a highly repetitive region like a centromere?
When looking for numerical abnormalities of certain chromosomes
What are chromosome paints?
A collection of fluorescently labelled chromosome specific probes that will hybridize along the entire length of a certain chromosome
Why would we do a chromosome paint?
Looking for numerical abnormalities or translocations
Why might we do molecular karyotyping at interphase over G-banding to look for aneuploidies?
Quicker than doing G-banding at metaphase
How can we separate chromosomes using flow cytometry?
Use dyes that bind differentially to different base pairs, one that prefers A/T bases and one that prefers G/C bases. Since different chromosomes have different size and base compositions, they’ll stain differently and the machine can use lasers to separate chromosomes based on the binding patterns of the dyes
Which chromosomes can’t we separate with flow cytometry?
9-12
How do we make a chromosome paint?
Separate one chromosome out from a bunch of lysed cells using flow cytometry, then derive a library from the separated chromosomes and label it with a fluorochrome. The paint is a cocktail of fragments
What is spektral karyotyping?
Multiplex FISH, is the simultaneous application of multiple chromosome paints
Can we use chromosome paints for all chromosomes at once?
Yes, we have enough dyes to do that
