Ploidy is a term used to indicate the number of basic chromosome number in a cell. The basic set of chromosomes in an organism is called the monoploid number. This number is indicated by x. In an organism, the ploidy of cells can vary. Humans and almost all mammals, have diploid cells. The gametes or sex cells (egg and sperm) are haploid cells.
What is a Diploid Cell?
According to the definition, it is an organism or cell that contains double set of chromosome (2n), one inherited from the mother and one inherited from father. Another definition also includes an individual that contains a double set of chromosome per cell. The somatic tissues of higher plants and animals contain diploid chromosome content.
Almost all animals have diploid number of cells. All the organisms that produce sexually, have two copies of chromosomes that have different origins, that is, paternal and maternal. This help in mixing of genes that gives rise to better progeny.
There are a few species that have haplodiploid cells. Here, one sex (mostly male) contains haploid cells and the other sex (female) has diploid cells. The male have developed from unfertilized eggs and the females develop from fertilized eggs. Thus, they have a complete set of chromosome. The example in such a case, includes insects like ants, bees and wasps, where the queen has diploid number of chromosome.
Another, example is the human race. Humans contain 2 set of chromosomes in their cells. The somatic cells or non-sex cells contains 46 chromosomes each. There are 22 sets of autosomal chromosomes and 1 set of sex chromosome. This brings the total to 23 sets of chromosomes. After fertilization, the somatic cells receive 23 chromosomes from each parent making the number of chromosomes in the cell 46.
The examples include all mammalian cells, except for a few species of mammals like the Red Vizcacha Rat (Tympanoctomys barrerae), Golden Vizcacha Rat (Pipanacoctomys aureus). Other examples are retrovirus that contains 2 copies of RNA genome. These include human foamy virus, human T-lymphotropic virus and HIV.
In our own body, all cells like skin cells, eye cells, cells of the kidney, etc. are diploid cells. The diploid number of chromosomes in the human body is 46. I hope this article has helped you understand more about these cells.