What Is A Diploid Cell?

Human karyotype
This human karyotype shows the complete set of human chromosomes. Each chromosome pair represents a set of homologous chromosomes in each diploid cell. Credit: somersault18:24/Science Photo Library/Getty Images

A diploid cell is a cell that contains two complete sets of chromosomes. This is double the haploid chromosome number. Each pair of chromosomes in a diploid cell is considered to be a homologous chromosome set. A homologous chromosome pair consists of one chromosome donated from the mother and one from the father. Humans have 23 sets of homologous chromosomes for a total of 46 chromosomes. Paired sex chromosomes are the X and Y homologs in males and the X and X homologs in females.

Diploid Cells

  • Diploid cells have two sets of chromosomes. Haploid cells have only one.
  • The diploid chromosome number is the number of chromosomes within a cell's nucleus.
  • This number is represented as 2n. It varies across organisms.
  • Somatic cells (body cells excluding sex cells) are diploid.
  • A diploid cell replicates or reproduces through mitosis. It preserves its diploid chromosome number by making an identical copy of its chromosomes and distributing its DNA equally between two daughter cells.
  • Animal organisms are typically diploid for their entire life cycles but plant life cycles alternate between haploid and diploid stages.

Diploid Chromosome Number

The diploid chromosome number of a cell is calculated using the number of chromosomes in a cell's nucleus. This number is abbreviated as 2n where n stands for the number of chromosomes. For humans, the diploid chromosome number equation is 2n = 46 because humans have two sets of 23 chromosomes (22 sets of two autosomal or non-sex chromosomes and one set of two sex chromosomes).

The diploid chromosome number varies by organism and ranges from 10 to 50 chromosomes per cell. See the following table for the diploid chromosome numbers of various organisms.

Diploid Chromosome Numbers

Organism

Diploid Chromosome Number (2n)

E.coli Bacterium 1
Mosquito 6
Lily 24
Frog 26
Humans 46
Turkey 82
Shrimp 254
Table of the diploid chromosome number for various organisms

Diploid Cells in the Human Body

All of the somatic cells in your body are diploid cells and all of the cell types of the body are somatic except for gametes or sex cells, which are haploid. During sexual reproduction, gametes (sperm and egg cells) fuse during fertilization to form diploid zygotes. A zygote, or fertilized egg, then develops into a diploid organism.

Diploid Cell Reproduction

Diploid cells reproduce through mitosis. In mitosis, a cell makes an identical copy of itself. It replicates its DNA and distributes it equally between two daughter cells that each receive a full set of DNA. Somatic cells go through mitosis and (haploid) gametes undergo meiosis. Mitosis is not exclusive to diploid cells.

Diploid 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 have life cycles that vacillate between diploid and haploid stages. 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.