Diploid organisms inherit one copy of each homologous chromosome from each parent all together, they are considered a full set of chromosomes. Homologous chromosomes are matched pairs containing the same genes in identical locations along their length. Somatic cells are sometimes referred to as “body” cells. In each somatic cell of the organism (all cells of a multicellular organism except the gametes or reproductive cells), the nucleus contains two copies of each chromosome, called homologous chromosomes. Most animals and plants are diploid, containing two sets of chromosomes. So, in addition to fertilization, sexual reproduction includes a nuclear division that reduces the number of chromosome sets. If the reproductive cycle is to continue, then the diploid cell must somehow reduce its number of chromosome sets before fertilization can occur again, or there will be a continual doubling in the number of chromosome sets in every generation. The number of sets of chromosomes in a cell is called its ploidy level. Cells containing two sets of chromosomes are called diploid. Haploid cells contain one set of chromosomes. If those two cells each contain one set of chromosomes, then the resulting cell contains two sets of chromosomes. Sexual reproduction requires fertilization, the union of two cells from two individual organisms. ![]() Explain the mechanisms within meiosis that generate genetic variation among the products of meiosis.Explain the differences between meiosis and mitosis.Describe cellular events during meiosis. ![]() Describe the behavior of chromosomes during meiosis.By the end of this section, you will be able to:
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