How many groups of chromosomes are distinguished in a human karyotype. What is the basis of this division?

All 22 autosomes are united in similarity into seven groups. (In size and shape) group A (from 1st to 3rd chromosomes) – three pairs of long chromosomes with equal or almost equal arms in length; group B (4th and 5th chromosomes) – two pairs of long chromosomes with shoulders of unequal length – different shoulders;
group C (from the 6th to the 12th chromosome) – a variety of medium sized chromosomes; they are difficult to individualize; the sex X chromosome also belongs to the same group in size;
group D (from the 13th to the 15th chromosomes) – medium-sized chromosomes having a very short, almost imperceptible second arm; they are all very similar to each other;
group E (from the 16th to the 18th chromosomes) – three pairs of short diverse chromosomes, and the chromosomes of the 16th pair differ from the 17th and 18th;
group F (19th and 20th chromosomes) – two pairs of very short equal-arm chromosomes; group G (chromosomes of the 21st, 22nd pairs) – very short one-arm chromosomes with satellites, which are difficult to distinguish from each other. The size of the group also includes the Y-chromosome.