Chromosomal abnormalities information Flashcards
(20 cards)
Frequency of chromosomal abnormalities in livebirths
0.6%
Frequency of chromosomal abnormalities in infertility
5%
Frequency of chromosomal abnormalities in first trimester SABs
50-60%
Frequency of chromosomal abnormalities in stillbirths and perinatal deaths
6%
Frequency of balanced translocations
Frequency of unbalanced translocations
balanced: 1/500
unbalanced: 1/2000
Frequency of pericentric inversion
1/100
What percent of all clinically recognized pregnancies end in SAB?
15%
Frequency of chromosomal abberrations in AMA women
1/50
Frequency of chromosomal aberrations in the general population
1/160
Risk of carrying a balanced translocation in the general population
1/500 (0.2%)
Level 1 mosaicism
1 abnormal cell in 1 sample
likely pseudomosaic; not reported
Level 2 mosaicism
> /=2 abnormal cells in one sample
usually considered pseudomosaicism
Level 3 mosaicism
> /= 2 abnormal cells in multiple samples
likely true mosaicism
Which cytogenetics test is best for unbalanced translocation?
aCGH - very high resolution!
Only use FISH if targeted
Which cytogenetics test is best for normal balanced translocations?
Karyotype - you can see the chromosomes themselves
Which cytogenetics test is best for mosaics?
FISH
Which cytogenetics test is best for CNVs?
aCGH
Approximately how many CNVs are there, and they take up what percent of the genome?
24,000 CNVs (mostly losses)
9.5% of the genome
Mechanisms of CNVs
1) Non-allelic homologous recombination
2) Non-homologous end-joining
3) insertion of mobile element
4) replication-based template switching
5) Chromothripsis
Genome-wide tests
microarray
NGS
