Diploid Cell Definition and Example

Diploid Cell Definition and Example A diploid cell is a cell that contains two sets of chromosomes. This is double the haploid chromosome number. Each pair of chromosomes in a diploid cell is considered to be one  homologous chromosome  set. A single chromosome set consists of two chromosomes, one of which is donated from the mother and the other from the father. Humans have 23 sets of homologous chromosomes. Paired sex chromosomes are the (X and Y) homologues in males and the (X and X) homologues in females. The somatic cells in your body are diploid cells. Somatic cells include all of the cell types of the body, except for the gametes or sex cells. Gametes are haploid cells. During sexual reproduction, gametes (sperm and egg cells) fuse at fertilization to form a diploid zygote. The zygote develops into a diploid organism. Diploid Chromosome Number The diploid chromosome number of a cell is the number of chromosomes in the cell nucleus. This number is commonly abbreviated as 2n, where n stands for the number of chromosomes. For humans, this equation would be 2n46. Humans have 2 sets of 23 chromosomes for a total of 46 chromosomes. Autosomal chromosomes (non-sex chromosomes): 22 sets of 2Sex chromosomes: 1 set of 2 The diploid chromosome number varies depending on the organism with most containing between 10 and 50 chromosomes per cell. Examples of organisms and their diploid chromosome numbers include: Organism Diploid Chromosome Number (2n) E.coli Bacterium 1 Mosquito 6 Lily 24 Frog 26 Humans 46 Turkey 82 Shrimp 254 Diploid Cell Reproduction Diploid cells reproduce by the process of mitosis. In mitosis, a cell makes an identical copy of itself allowing its DNA to be replicated and distributed equally between two daughter cells. Somatic cells go through the mitotic cell cycle, while gametes are reproduced by meiosis. In the meiotic cell cycle, four daughter cells are produced instead of two. These cells are haploid containing half the number of chromosomes as the original cell. Polyploid and Aneuploid Cells The term ploidy refers to the number of chromosome sets found in a cells nucleus. Chromosome sets in diploid cells occur in pairs, while haploid cells contain half the number of chromosomes as a diploid cell. A cell that is polyploid has extra sets of homologous chromosomes. The genome in this type of cell contains three or more haploid sets. For example, a cell that is triploid has three haploid chromosome sets and a cell that is tetraploid has four haploid chromosomes sets. A cell that is aneuploid contains an abnormal number of chromosomes. It may have extra or missing chromosomes or may have a chromosome number that is not a multiple of the haploid number. Aneuploidy occurs as a result of chromosome mutation that happens during cell division. Homologous chromosomes fail to separate correctly resulting in daughter cells with either too many or not enough chromosomes. Diploid and Haploid Life Cycles Most plant and animal tissues consist of diploid cells. In multicellular animals, organisms are typically diploid for their entire life cycles. Plant multicellular organisms, such as flowering plants, have life cycles that vacillate between periods of a diploid stage and a haploid stage. Known as alternation of generations, this type of life cycle is exhibited in both non-vascular plants and vascular plants. In liverworts and mosses, the haploid phase is the primary phase of the life cycle. In flowering plants and gymnosperms, the diploid phase is the primary phase and the haploid phase is totally dependent upon the diploid generation for survival. Other organisms, such as fungi and algae, spend the majority of their life cycles as haploid organisms that reproduce by spores. Key Points Diploid cells are cells with two sets of chromosomes. They have twice the chromosome number of haploid cells.Somatic cells (body cells excluding sex cells) are examples of diploid cells.The diploid chromosome number is the number of chromosomes within a cells nucleus.The diploid chromosome number is represented as 2n and varies among different organisms.A diploid cell replicates by mitosis and preserves the diploid chromosome number by making identical copies of its chromosomes and distributing them equally between two daughter cells.Animal organisms are typically diploid for the entirety of their life cycles.Plant life cycles alternate between diploid and haploid stages.