Difference between Haploid and Diploid

All living organisms have genes that contain distinct traits and qualities inherited from the parents. Genes are found on chromosomes – the structural organization of DNA.

Sexually reproducing organisms have the genetic materials of both parents, which means they have two sets of chromosomes (diploid).

What is a chromosome?

It is a double-helix structure where protein and DNA can be found. Specifically, chromosomes are DNA strands containing genes found in living organisms. The number of sets of chromosomes in a cell is referred to as ploidy, which contains two sets of chromosomes (diploid).

Different organisms have different numbers of chromosomes.
Humans, in nature, are diploid as they have two complete sets of chromosomes, 23 from the mother cell and 23 from the father cell, bringing the total to 46 chromosomes.
For sexually reproducing organisms to reproduce they need to create gametes or sex cells with a haploid (half the number of chromosomes.
Once the two haploid gametes fuse, they will form a diploid cell known as the zygote, which will grow and develop into a new organism. ^{(1, 2, 3, and 4)}

What is haploid?

A haploid is nuclei that only has one set of chromosomes containing a single copy of the gene for each trait. The organism’s sex cells are haploid and came from diploid cells through the process of meiosis.

Bacteria and fungi also contain haploid cells. If the haploid cells from both male and female fuse during the process of fertilization, it will form a diploid cell. ^{(2, 3)}

What is diploid?

Diploid pertains to nuclei that contain pairs of homologous chromosomes. It has two copies of genes (alleles for each trait.

An organism’s somatic cell is diploid as the process of mitosis makes it possible to create new diploid cells. You can find diploid cells in most plants and animals. ^{(2, 3)}

Basis for Comparison	Diploid	Haploid
Meaning/Definition	They are organisms/cells that have two sets of chromosomes (one from each parent cell)	They contain only a single copy of each chromosome.
Symbol	2n	n
Etymology	Greek word diplous meaning double. ⁽⁴⁾	Greek word haplous meaning single. ⁽⁴⁾
How they are formed/reproduced?	How they are formed/reproduced?	They are formed during the process of meiosis – a reduction cell division wherein the diploid cell divides and the result is a haploid germ cell.
Number of chromosomes	The exact number of chromosomes depends on the specific species. In humans, a diploid cell contains 23 pairs of chromosomes bringing the total chromosomes to 46.⁽⁵⁾	They contain a single set of chromosomes – half the number of chromosomes found in diploid cells. In humans, haploid cells have a total of 23 chromosomes. ⁽⁵⁾
Cell type	Often seen in somatic cells of most vertebrates	Often seen in sex cells/gametes of most vertebrates.
Type of eggs	They grow from fertilized eggs (the fertilization of two haploid cells).	They grow from unfertilized eggs.
Similarity with the parent cells	They are genetically similar or identical to the parent cell.	They are not genetically identical with the parents and the reason is because of the crossing over during meiosis.
Alternation of generation	It is the sporophytic stage, which is less predominant when compared with the haploid stage in the bryophyte life cycle such as the mosses. However, it is a more predominant Pteridophyta life cycle such as the ferns. ^{(5, 6)}	It is called the gametophytic stage, which is more predominant than the diploid stage in the bryophyte life cycle such as mosses. However, they are less predominant than diploid in the Pteridophyta life cycle. ^{(5, 6)}
Significance	They are essential in the organism’s growth and development. The majority of cells in the body are diploid and they carry most of the functions of the body. They are also essential for the growth of cells and tissue healing. The shedding and replacement of epithelial cells are all because of mitosis, which diploid cells have a major role to play. ^{(6, 7)}	They are vital in sexual reproduction and genetic diversity.
Use in a higher form of organisms	In humans and other higher organisms, all cells are diploid except the sex cells.	Haploid cells are used for sex cells only.
Examples of organisms	Humans Fishes Frogs Most plants	Hymenoptera Bees Ants (male) Wasps
Examples at the cellular level	Somatic cells (non-sex cells) such as skin cells, blood cells, and muscle cells	Gametes (male/female germ cells) such as the sperm and ova
Ability to adapt	They adapt slower than haploid.⁽⁷⁾	They adapt faster than diploids.

Important things to know about chromosomes:

Chromosomes contain the cell’s DNA and protein where the DNA contains genetic information and proteins control the functions of the DNA.
It is the fundamental basis of life.
It contains the coding for everything – from the physical feature to the likelihood of having disease conditions.
A malfunction in the copy of chromosomes can lead to birth defects, cancer, and other conditions.
There are about 220 somatic cell types in humans. ^{(7, 8, and 9)}

Key terms to keep in mind when studying chromosomes, haploid, and diploid.

When you study chromosomes, specifically haploid and diploid, there are common terms you will encounter, and as such you need to familiarize by heart. These include:

Ploidy – It pertains to the number of sets of chromosomes found in the cell of an organism.
Diploid – It pertains to organisms with two sets of chromosomes.
Haploid – It pertains to organisms with one set of chromosomes.
Polyploidy – It is a unique condition where the cell has chromosomes with multiple diploid chromosome number.
Tetraploid – It pertains to four sets of chromosomes.
Hexaploid – It pertains to six sets of chromosomes.
Gametogenesis – The process of using meiosis to equally divide the chromosomal set.
Fertilization – It is when two cells unite or bind to form a zygote.
Zygote – It is a eukaryotic cell that results from the fertilization of two gametes. ^{(8, 9, and 10)}

Summary of key differences between haploid and diploid

Diploid cells have pairs of homologous chromosomes while haploid only has one set of chromosomes.
The nuclei of diploid cells have two gene copies or alleles for each trait while the nuclei of haploid only have a single allele or copy of the gene for each trait.
Somatic cells are diploid while all sex cells are haploid.
New diploid cells are created through the process of mitosis while new haploid cells are created through meiosis.
Most animals and plants have diploid cells while haploid cells can also be found in organisms other than animals and plants such as fungi and bacteria.

Haploid and diploid cells are essential in sexual and asexual reproduction. They occur in nature and differ greatly in sets or number of chromosomes as well as the type of cells which they occur.

Haploid cells have half of the total number of chromosomes in the diploid cells. Haploid cells are reproduced during the process of meiosis whereas diploid cells are reproduced during mitosis.

Always remember that the number of chromosomes varies in different organisms. Humans have a complete set of chromosomes, a total of 46 chromosomes. ^{(3, 7, 9, and 10)}

References

https://microbenotes.com/diploid-vs-haploid/
https://www.diffen.com/difference/Diploid_vs_Haploid
https://byjus.com/biology/difference-between-haploid-and-diploid/
https://www.youtube.com/watch?v=zglQ2Ildw4I
https://www.albert.io/blog/diploid-vs-haploid-similarities-differences/
https://www.vedantu.com/biology/difference-between-haploid-and-diploid
https://www2.estrellamountain.edu/faculty/farabee/biobk/BioBookmeiosis.html
https://www.cell.com/current-biology/pdf/S0960-9822(08)01268-2.pdf
http://www.bozemanscience.com/diploid-vs-haploid
https://www.eolss.net/Sample-Chapters/C03/E6-53-01-04.pdf