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Detail re. etiology / mention haploid cells
'''Chromosomes''' are packaged units of [[DNA]] and associated proteins.<ref>http://learn.genetics.utah.edu/units/disorders/karyotype/whatarechrom.cfm</ref> The chromosome carries portions of the hereditary information of an organism. The DNA is tightly coiled many times around proteins called [[histones]] that support the chromosome structure.<ref>http://ghr.nlm.nih.gov/handbook/basics/chromosome</ref> The bound DNA units are called [[nucleosomes]].
'''Chromosomes''' (literally: ''colored bodies'', from [[Greek]) are packaged units of [[DNA]] and associated proteins.<ref>http://learn.genetics.utah.edu/units/disorders/karyotype/whatarechrom.cfm</ref> The chromosome carries portions of the hereditary information of an organism. The DNA is tightly coiled many times around proteins called [[histones]] that support the chromosome structure.<ref>http://ghr.nlm.nih.gov/handbook/basics/chromosome</ref> The bound DNA units are called [[nucleosomes]].
==Physical Characteristics of Chromosomes==
==Physical Characteristics of Chromosomes==
==Cell Division==
==Cell Division==
Chromosomes are visible only during cell division, when the DNA is super coiled and condensed to facilitate distribution into daughter cells. Cell division in somatic cells (mitosis) results in the creation of daughter cells with the same number of chromosomes as the original cell, a total of 46 chromosomes in a human. Cell division in the germ cells, eggs and sperm (meiosis), results in the creation of daughter cells with half the number of chromosomes as the original cell. This reduction in the number of chromosomes is important so that the original number of chromosomes is restored following fertilization of the egg by the sperm.
Chromosomes are visible only during cell division, when the DNA is super coiled and condensed to facilitate distribution into daughter cells. Cell division in somatic cells (mitosis) results in the creation of daughter cells with the same number of chromosomes as the original cell, a total of 46 chromosomes in a human. Cell division in the germ cells, eggs and sperm (meiosis), results in the creation of daughter cells with half the number of chromosomes as the original cell (haploid cells). This reduction in the number of chromosomes is important so that the original number of chromosomes is restored following fertilization of the egg by the sperm.
==Karyotype Analysis==
==Karyotype Analysis==