Diploid cell

Overview

Ploidy is the number of chromosomal sets found in a cell; it is indicated by “n”. Based on the number of sets of chromosomes, cells can be classified as –

• Haploid
• Diploid
• Polyploid

Cells are classified based on the count of chromosomes, as seen below –

What is a Diploid cell? – Diploid cell Meaning

The term diploid refers to the count of chromosomes that an entity has. A diploid cell is a cell containing two complete sets of chromosomes. Diploid cells have paired chromosomes, each being obtained from each of the biological parents.

This number is double the number of chromosomes seen in haploid conditions. Each pair of the chromosomes in diploid cells are homologous chromosomes sets, wherein each chromosome pair possesses a chromosome contributed from the mother and father.

Diploid cells in Human body

Humans are diploid (2n), hence each human has two copies of chromosomes in the nucleus of their cells. This is to say that there are two copies of chromosome 1, two copies of chromosome 2, two copies of chromosome 3 and so on. Other than the human sex cells, all cells are diploid, having 23 pairs of chromosomes. The sex cells in humans determine their sex/gender (sperms cells and eggs), which comprises a single set of chromosomes, referred to as haploid. This is the only instance wherein the homologous pair does not comprise two copies of the same chromosome.

In other words, humans have 23 sets of homologous chromosomes, a total of 46 chromosomes, hence 2n = 46. In males, the paired sex chromosomes are X and Y homologs (XY), while in females it is the X and X homologs (XX).

In our body, all the somatic cells are diploid except for sex cells, they are haploid. At the time of sexual reproduction, the sex cells or gametes unite at the time of fertilization, forming a diploid zygote. A fertilized egg or zygote develops into a diploid entity.

Features of diploid cells

• Possess two sets of chromosomes while haploid cells have one set of chromosome
• They are represented as 2n and is different for different species
• This chromosome number is their number inside the nucleus of the cell
• The cells which are somatic in nature in the body are diploid
• Diploid cells reproduce through mitosis, and conserve their number of chromosomes by generating a copy of its chromosomes, and equally distributing their DNA amongst their daughter cells

How many chromosomes are in a diploid cell?

One can calculate the number of chromosomes in a diploid cell’s nucleus. This number is represented as 2n, “n” here stands for the number of chromosomes. The diploid chromosome number equation for humans for instance is represented as 2n=46, for chicken, it is 2n=78 etc.

Here, humans have 2 sets of 23 chromosomes – 22 sets of two non-sex or autosomal chromosomes and one set of two sex chromosomes.

The diploid number varies between species. Take a look at the table below to know the chromosome number of different species.

Chromosome number of different species:

Diploid cell Example

Diploid animals remain diploid all through their life. This is not the case in many plants, as they have a tendency to alter their ploidy from being diploid to haploid and haploid to diploid. This is what is referred to as the alternation of generations, wherein there is an alteration between two phases of ploidy.

When the plant cycle is in its diploid phase, it is referred to as the sporophytic phase and when in the haploid phase of its cycle, it is referred to as the gametophytic phase. In the life span of Pteridophytes, the predominant phase is that of the sporophytic phase.

Humans have the majority of body cells as diploids (2n). Some of the examples of diploid cells in humans are –

• Blood cells
• Muscle cells
• Bone cells
• Skin cells

All these cells comprise two full sets of chromosomes.

Diploid cells vs. Haploid cells

The ploidy of diploid cells differs from that of haploid cells. Haploid cells comprise one set of chromosomes, as opposed to two full sets of chromosomes seen in diploid cells.

Haploid cells

Haploid cells comprise one set of chromosomes only. A good example of haploid cells are sex cells seen in humans. The production of these cells is by the process of meiosis. When the haploid cells obtained from each of the biological parent – male and female gametes unite at the time of fertilization, a diploid cell is formed.

Nuclei in haploid cells comprise one gene copy for each of the characteristics. All the sex cells in the entity are haploid, which finds their origin from the diploid cells through meiotic division. These haploid cells can be observed in bacteria (asexual mode).

Difference between Diploid cells and Haploid cells

Following are a few key differences between diploid cells and haploid cells –

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