There are two types of cells in the body - haploid cells and diploid cells. The difference between haploid and diploid cells is related to the number of chromosomes that the cell contains.
|About||Diploid cells contain two complete sets (2n) of chromosomes.||Haploid cells have half the number of chromosomes (n) as diploid - i.e. a haploid cell contains only one complete set of chromosomes.|
|Cell Division and Growth||Diploid cells reproduce by mitosis making daughter cells that are exact replicas.||Haploid cells are a result of the process of meiosis, a type of cell division in which diploid cells divide to give rise to haploid germ cells. A haploid cell will merge with another haploid cell at fertilization.|
|Examples||Skin, blood, muscle cells (also known as somatic cells)||Cells used in sexual reproduction, sperm and ova (also known as Gametes).|
Brief Introduction to the Chromosome
A chromosome is a double-helix structure that houses DNA and protein in cells. It is a strand of DNA that contains genes found in living organisms. It also contains proteins, which help package the DNA and control its functions. A homologous chromosome is a chromosome pair of the same length, centromere position, and staining pattern with genes for the same characteristics at corresponding loci (location).
Since ploidy refers to the number of sets of chromosomes in a biological cell, a cell containing two sets of chromosomes comes to be known as a diploid cell. Humans have a total of 23 pairs of chromosomes, which brings it to a total of 46. (23 X 2) Twenty two of these pairs are autosomal in nature, i.e. they lend non-sexual characteristics while the last pair is known as the sex chromosome. A haploid cell, on the other hand, is that cell which contains only one set of chromosomes in it. Haploid cells are found in various algae, various male bees, wasps and ants. Haploid cells should not be confused with monoploid cells as the monoploid number refers to the number of unique chromosomes in one biological cell.
All animal cells have a fixed number of chromosomes in their body cells which exist in homologous pairs (2n). Each pair of chromosomes consists of one chromosome from the mother and the second from the father. During the process of meiosis (cell division for sexual reproduction), the sex cells divide to produce "gametes" which then contain only one set of the chromosomes (n).
When the male and female gametes fuse during fertilization and zygote formation, the chromosome number is restored to 2n again. Thus, diploid cells are those which contain a complete set (or 2n number) of chromosomes whereas haploid cells are those that have half the number of chromosomes (or n) in the nucleus. In plant cells, the haploid or n stage constitutes a large part of the life cycle.
Which Cells are Haploid?
Gametes or germ cells are haploid cells (example: sperm and ova) containing only one set (or n) number of chromosomes and autosomal or somatic cells are diploid cells containing 2n number of chromosomes. The number of chromosomes (n) differs in different organisms. In humans a complete set (2n) comprises of 46 chromosomes.
Cell Division and Growth
Haploid cells are a result of the process of meiosis, a type of reductional cell division in which diploid cells divide to give rise to haploid germ cells or spores. During meiosis, a diploid germ cell divides to give rise to four haploid cells in two rounds of cell division. This process does not occur in organisms (example bacteria) that reproduce via asexual processes like binary fission.
During the process of reproduction, haploid cells (male and female) unite to form a diploid zygote. Cell growth is the result of mitosis; it is a process by which mother cells divide to give rise to identical daughter cells with equal number of chromosomes. This process differs slightly in different types of cells, animal cells undergoing "open" mitosis with the breakdown of nuclear membrane, whereas organisms like fungi and yeast undergo closed mitosis with an intact nuclear membrane.
Ploidy is the complete set of chromosomes in a cell. In humans most somatic cells are in a diploid state and only switch to a haploid state in gametes or sex cells. In algae and fungi cells switch between a haploid and diploid state over the length of their life cycle (known as alternation of generation), and are in a haploid state during the principle stage of their life cycle.
Polyploidy refers to a state where multiple sets of chromosomes are present. This is commonly seen in plant cells but not in animal cells.
A spermatogonium (primordial germ cell) is a good example of a diploid cell.
In animals, haploid cells are found in the sex cells. Male bees, wasps, and ants are haploid because of the way they develop: from unfertilized, haploid eggs.
Video explaining the differences
These videos explain the differences between haploid and diploid cells:
This video from Khan Academy explains the concepts in more detail: