Lecture 7: Cytogenomics Flashcards
What is a chromosome?
1 molecule of DNA compacted together as a result of Protein-DNA interactions
The p arm is _______ the q arm is _______
Short
Long
What is a metacentric chromosome?
The centromere is positioned so the p arm is almost as long as the q
What is a submetacentric chromosome?
The centromere is positioned so the p arm is definitely shorter than the q arm
What is an acrocentric chromosome?
The centromere is positioned so short it’s hard to observe (satellite region)
What are the 2 types of chromosome abnormalities?
Numerical: extra or missing chromosomes
Structural: abnormal structure
What causes numerical errors?
Faulty cell division or fertilisation errors
What is a euploid abnormality?
A disorder with multiples of the haploid set i.e. triploidy (3 of each chromosome), tetraploidy (4 of each chromosome)
What is an aneuploidy abnormality?
A disorder where there is gain or loss of one or more chromosomes
What causes structural abnormalities?
Translocations, Insertions, Deletions etc.
What is a balanced structural abnormality?
There is no net gain/loss of genetic material
What is an unbalanced structural abnormality?
There is a net gain/loss of genetic material
What are Robertsonian translocations?
A balanced translocation between 2 acrocentric chromosomes.
What is a reciprocal translocation?
The balanced exchange of genetic material between 2 non-homologous chromosomes
Are insertions balanced?
Yes as long as there is no net gain/loss of material
Are inversions balanced?
Yes
Are deletions balanced?
No
Are duplications balanced?
No
What is a terminal deletion/duplication?
A deletion/duplication that occurs at the extremes of the chromosomes (on the ends not attached to the centromere)
What is an interstitial deletion/duplication?
A deletion/duplication that occurs in the middle of either arm on the chromosomes
What are the clinical impacts of cytogenomic variants?
No apparent effect (balanced or mosaic) Reproductive issues (structural) Apparent effects (unbalanced)
What are isochromosomes?
Instead of normal separation of sister chromatids, the 2 short arms separate together and the 2 long arms separate together (unbalanced)
What is mosaicism?
Presence of cell lines with different chromosomal constitutions in the same individual (can be numerical or structural changes)
