Chromosome

A carrier of genetic information that is visible under an ordinary light microscope. Each human chromosome has two arms: the p (short) arm, and the q (long) arm. Generally, the nucleus of a human cell contains two sets of chromosomes (each set is called an allele) - one allele given by each parent. Each allele has 23 single chromosomes: 22 autosomes (non-sex chromosome); and an X /Y sex chromosome combination denoting male, or an X/X sex chromosome combination denoting female (one X chromosome is given by the mother, and either an X chromosome or a Y chromosome is randomly given by the father). A chromosome contains roughly equal parts of protein and DNA. The chromosomal DNA contains an average of 150 million nucleotide building blocks. These nucleotide building blocks are known as bases.