Genetics Flashcards
Fluorescent staining
For chromosomes within the nucleus e.g. chromosome 11
How a chromosome is recognised
- Banding pattern with specific stains
- Length
- Position of centromere
Anueploidy
Whole or extra missing chromosome
Translocation
Rearrangement of chromosomes
Robertsonian translocation
Two acrocentric chromosomes stuck end to end
Robertsonian translocation and pregnancy?
Increases risk of trisomy
(because of meiosis etc & you have this double decker chromosome = 2. So 2 + 1 (1 is normal) = 3
Most common form of robertsonian translocation
Most common robertsonian translocations are between chromosomes 14 and 21
Recurrence of Down Syndrome
- Approximately 1% if child has primary trisomy 21
- Higher if caused by robertsonian translocation
47 XY + 18
so 47 chromosomes where you have 3 copies/trisomy 18
Edward Syndrome
45X
Turner syndrome
47XXX
Triple x
47XXY
Klinefelters
Trisomy 18
Edward syndrome
Why is X chromosome aneuploidy better tolerated?
X inactivation (i.e. only ever 1 active X chromosome in cells at any one time)
Reciprocal translocations: alternate, adjacent-1, adjacent-2. Which one would you want?
Alternate –> normal and balanced.
Adjacent-1 and adjacent-2 will result in imbalance
Reciprocal translocation reproductive risks
for most translocations, ~50% of conceptions will have either normal chromosomes or the balanced translocation
unbalanced products result in –
miscarriage (large segments)
dysmorphic delayed child (small segments)
How could you detect translocations?
FISH
22q11 deletion?
DiGeorge syndrome
The result of the 22q11.2 deletion is a range of embryonic developmental disruptions involving the head, neck, brain, skeleton, and kidneys. Portions of the heart, head and neck, thymus, and parathyroids derive from the third and fourth pharyngeal pouches, and a developmental field defect results from the chromosomal deletion. This, in turn, leads to hypocalcemia and variable T-cell deficiency.
How could you detect diGeorge syndrome?
FISH (i.e. band/probe-y bit won’t show up)
HER2 protein in cancer and looking at it?
HER2 protein over expression found in breast cancer.
Because proteins are made by genes then you could look at the genes.
Look at the genes by using FISH :D
Genome wide investigation
Array CGH
Specific loci or chromosomes
Quantitive PCR
Prenatal cytogenetic investigation
QF-PCR
quantitive fluorescent PCR
Why is QF-PCR good?
Allows you to copy small sections of DNA in order to precisely quantify the amount of DNA present
