<P> After the completion of binary fission or cell reproduction involving mitosis, each daughter cell has the same amount of DNA (Z) as what the parental cell had before it replicated its DNA . These two types of cell reproduction produced two daughter cells that have the same number of chromosomes as the parental cell . Chromosomes duplicate prior to cell division when forming new skin cells for reproduction . After meiotic cell reproduction the four daughter cells have half the number of chromosomes that the parental cell originally had . This is the haploid amount of DNA, often symbolized as N. Meiosis is used by diploid organisms to produce haploid gametes . In a diploid organism such as the human organism, most cells of the body have the diploid amount of DNA, 2N . Using this notation for counting chromosomes we say that human somatic cells have 46 chromosomes (2N = 46) while human sperm and eggs have 23 chromosomes (N = 23). Humans have 23 distinct types of chromosomes, the 22 autosomes and the special category of sex chromosomes . There are two distinct sex chromosomes, the X chromosome and the Y chromosome . A diploid human cell has 23 chromosomes from that person's father and 23 from the mother . That is, your body has two copies of human chromosome number 2, one from each of your parents . </P> <P> Immediately after DNA replication a human cell will have 46 "double chromosomes". In each double chromosome there are two copies of that chromosome's DNA molecule . During mitosis the double chromosomes are split to produce 92 "single chromosomes", half of which go into each daughter cell . During meiosis, there are two chromosome separation steps which assure that each of the four daughter cells gets one copy of each of the 23 types of chromosome . </P> <P> Though cell reproduction that uses mitosis can reproduce eukaryotic cells, eukaryotes bother with the more complicated process of meiosis because sexual reproduction such as meiosis confers a selective advantage . Notice that when meiosis starts, the two copies of sister chromatids number 2 are adjacent to each other . During this time, there can be genetic recombination events . Parts of the chromosome 2 DNA gained from one parent (red) will swap over to the chromosome 2 DNA molecule that received from the other parent (green). Notice that in mitosis the two copies of chromosome number 2 do not interact . It is these new combinations of parts of chromosomes that provide the major advantage for sexually reproducing organisms by allowing for new combinations of genes and more efficient evolution . However, in organisms with more than one set of chromosomes at the main life cycle stage, sex may also provide an advantage because, under random mating, it produces homozygotes and heterozygotes according to the Hardy - Weinberg ratio . </P> <P> A series of growth disorders can occur at the cellular level and these consequently underpin much of the subsequent course in cancer, in which a group of cells display uncontrolled growth and division beyond the normal limits, invasion (intrusion on and destruction of adjacent tissues), and sometimes metastasis (spread to other locations in the body via lymph or blood). </P>

How does cell enlargement help the growth of a baby