NEET BIOLOGY

Detailed explanation-1: -According to international conventions, human autosomes, or non-sex chromosomes, are numbered from 1 to 22, in descending order by size, with the exceptions of chromosomes 21 and 22, the former actually being the smallest autosome. The sex chromosomes are generally placed at the end of a karyogram.

Detailed explanation-2: -In a human karyotype, autosomes or “body chromosomes” (all of the non–sex chromosomes) are generally organized in approximate order of size from largest (chromosome 1) to smallest (chromosome 22).

Detailed explanation-3: -Two copies of chromosome 21, one copy inherited from each parent, form one of the pairs. Chromosome 21 is the smallest human chromosome, spanning about 48 million base pairs (the building blocks of DNA) and representing 1.5 to 2 percent of the total DNA in cells.

Detailed explanation-4: -A karyotype is an organized profile of a person’s chromosomes. Two chromosomes specify sex, XX for female and XY for male. The rest are arranged in pairs, numbered 1 through 22, from largest to smallest. This arrangement helps scientists quickly identify chromosomal alterations that may result in a genetic disorder.

Detailed explanation-5: -The largest autosome-chromosome 1-has approximately 2, 800 genes; the smallest autosome-chromosome 22-has approximately 750 genes.