W01_04 Clinical cytogenetics 2

Question 1

what does “del(18)(q23)dn” mean?

Answer 1

de novo deletion of the long arm of chromosome 18

Question 2

what’s contiguous gene deletion syndrome?

Answer 2

deletion of multiple genes along a stretch of DNA

Question 3

how does a ring chromosome abnormality form?

Answer 3

telomeres gone from each end, and the DNA wraps itself to cover the ends

Question 4

what does 46,XY,der(14,21),(q10;q10)pat,+21 mean?

Answer 4

derivative of long arms of 14 and 21 from paternal side. long arm of 21 adds an extra 21 chromosome arm, so it’s essentially a trisomy 21

Question 5

note: if someone has both derivatives of broken chromosomes, they’ll be normal carriers

Answer 5

ok

Question 6

what’s the philadelphia rearrangement?

Answer 6

translocation of ABL1 (chr9) and BCR (chr22);

somatic!

Question 7

what does FISH stand for? (genetics)

Answer 7

fluorescence in situ hybridization;

small probe to detect presence of abnormality (150kb)

Question 8

what’s a genomic disorder?

Answer 8

small recurrent deletions or duplications in the genome. some can be frequent enough to be a syndrome. can’t be seen with g-banding - have to be seen with microarray or FISH

Question 9

what’s NAHR?

Answer 9

non-allelic homologous recombination;

results in duplications/deletions during this recombination

Question 10

note: microarrays are like 1000s of FISH tests at once

Answer 10

ok

Question 11

what does microdeletion 22q11.2 result in?

Answer 11

diGeorge syndrome;
usually about 3Mb deletion;
conotruncal heart defects, facial dysmorphism, cleft palate, thymic/parathyroid defects, hypocalcemia, developmental disability

Question 12

what’s william’s syndrome?

Answer 12

7q11.23 deletion;

happy (social butterfly), learning difficulties, small size, facial features, congenital heart defect

Question 13

what’s 7q11.23 duplication syndrome?

Answer 13

socially inhibited (cognitive deficits, autism, schizophrenia risk), speech delay

Question 14

note: Low Copy Repeats can lead to duplication/deletion syndromes

Answer 14

ok

Question 15

suspected aneuploidy for 21, 13, 18, x, y, chromosomal mosaicism, infertility, miscarriages. what the suggested technique to test them with?

Answer 15

G-banding

Question 16

note: use FISH and trio analysis to check for inheritance pattern, de novo mutation

Answer 16

ok

Question 17

note: copy number variations are present in the healthy population

Answer 17

ok