Cytogenetics: Chromosomes and Karyotype Analysis

A karyotype is the number and appearance of chromosomes in the nucleus of a eukaryotic cell.

Human chromosome 2 is now known to be a result of an end-to-end fusion of two ancestral ape chromosomes. It is the second largest human chromosome.

The sex of an unborn fetus can be determined by observation of interphase cells. DNA is in replication stage at interphase, therefore observation of fetal DNA is very convenient.

Differences in absolute size of chromosomes were probably due to different amounts of DNA duplication.

The ploidy in which the chromosome number in the cells is not the typical number for the species is termed aneuploidy.

In karyotype analysis, a silver stain can be used to identify the NOR silver nitrate inserts into the NOR-associated protein in the stalks and satellites, staining the proteins dark black.

All the three replication processes are observed in Apicomplexa.

Paratomy is a form of asexual reproduction in animals where the organism splits in a plane perpendicular to the antero-posterior axis and the split is preceded by the pregeneration of the anterior structures in the posterior portion.

Q-banding is a fluorescent pattern obtained using quinacrine for staining. Quinacrin (atebrin) binds both regions rich in AT and in GC, but only the AT-quinacrin-complex fluoresces. Since regions rich in AT are more common in heterochromatin than in euchromatin, these regions are labelled preferentially.

Polytene chromosomes are found in drosophila. Here, chromosome replicates several times and becomes exceptionally giant size called polytene.

Heterochromatin is only found in eukaryotes.

The fundamental number, FN, of a karyotype is the number of visible major chromosomal arms per set of chromosomes.

The dark regions on G-banding tend to be heterochromatin.

Bladder cancer is a disease related to chromosome 4. 54 cancer genes are located in this chromosome.

The Hayflick limit has been found to correlate with the length of the telomere region.