Chromosome: Difference between revisions

The number of genes per chromosome, the number of chromosomes, and the length of chromosomes varies considerably among the various organisms on [[Earth]]. Humans have 24 different chromosomes (22 pairs of autosomes plus 2 sex chromosomes), 46 total chromosomes with about 1000 genes each (30 to 38 thousand genes per cell). The human chromosomes range in size from 50 x 10⁶ nucleotides in length, which is equal to 1.7 cm if fully extended - up to 250 x 10⁶ nucleotides in the largest (which would extend 8.5 cm).[http://www.ncbi.nlm.nih.gov/books/bv.fcgi?tool=bookshelf&call=bv.View..ShowSection&searchterm=h1&rid=cell.section.1607] The [[DNA]] in a single human cell would extend over 2 meters if attached end-to-end. However, during cell division ([[mitosis]]) the chromosomes condense into structures about 5µm long, which are then visible when stained under a standard [[compound microscope]].