Ploidy

diploidhaploid2nchromosome numberdiploid numbertetraploiddiploidsdiploidyeuploiddiploid chromosome number
Ploidy is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes.wikipedia
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Autosome

autosomalautosomal DNAautosomes
Ploidy is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. After fusion of a male and a female gamete (fertilization) both containing 1 set of 23 chromosomes, the resulting zygote has 46 chromosomes: 2 sets of 23 chromosomes (22 autosomes, and 1 allosome).
The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosome pairs which may have different structures.

Allele

allelesallelicmultiple alleles
Ploidy is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes.
Most multicellular organisms have two sets of chromosomes; that is, they are diploid.

Meiosis

meioticsyzygymeiosis I
The haploid number for humans (half of 46) is 23; and the monoploid number equals 46 divided by the ploidy level of 2, which is also 23. When a human germ cell undergoes meiosis, the two sets of 23 chromosomes are split in half to form gametes.
Meiosis (from Greek μείωσις, meiosis, which means lessening) is a specialized type of cell division that reduces the chromosome number by half, creating four haploid cells, each genetically distinct from the parent cell that gave rise to them.

Sperm

sperm cellspermatiasperm cells
The number of chromosomes found in a single complete set of chromosomes is called the monoploid number (x). In most animals, the haploid number (n) is unique to gametes (sperm or egg cells), and refers to the total number of chromosomes found in a gamete, which under normal conditions is half the total number of chromosomes in a somatic cell. Gametes (sperm and ova) are haploid cells.
The human sperm cell is haploid, so that its 23 chromosomes can join the 23 chromosomes of the female egg to form a diploid cell.

Cellular differentiation

differentiationcell differentiationdifferentiate
However, in many situations somatic cells double their copy number by means of endoreduplication as an aspect of cellular differentiation.
Most cells are diploid; they have two copies of each chromosome.

Chromosome

chromosomeschromosomalChromosomal number
Ploidy is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. The nucleus of a eukaryotic cell is haploid if it has a single set of chromosomes, each one not being part of a pair.
For example, most eukaryotes are diploid, like humans who have 22 different types of autosomes, each present as two homologous pairs, and two sex chromosomes.

Polyploidy

tetraploidpolyploidtriploid
Somatic cells, tissues and individuals can be described according to the number of sets present (the ploidy level): monoploid (1 set), diploid (2 sets), triploid (3 sets), tetraploid (4 sets), pentaploid (5 sets), hexaploid (6 sets), heptaploid or septaploid (7 sets), etc. The generic term polyploid is used to describe cells with three or more chromosome sets. Tetraploidy (four sets of chromosomes, 2n = 4x) is common in plants, and also occurs in amphibians, reptiles, and insects.
Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two sets of chromosomes—one set inherited from each parent.

Einkorn wheat

einkornT. monococcumprimitive wheat species
The gametes are haploid for their own species, but triploid, with three sets of chromosomes, by comparison to a probable evolutionary ancestor, einkorn wheat.
Einkorn is a diploid species (2n = 14 chromosomes) of hulled wheat, with tough glumes ('husks') that tightly enclose the grains.

Zygote

zygoticzygotesfertilized egg
After fusion of a male and a female gamete (fertilization) both containing 1 set of 23 chromosomes, the resulting zygote has 46 chromosomes: 2 sets of 23 chromosomes (22 autosomes, and 1 allosome).
In plants, the zygote may be polyploid if fertilization occurs between meiotically unreduced gametes.

Cell (biology)

cellcellscellular
Ploidy is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes.
A diploid cell may also undergo meiosis to produce haploid cells, usually four.

Germ cell

germ cellsprimordial germ cellsgerm
The haploid number for humans (half of 46) is 23; and the monoploid number equals 46 divided by the ploidy level of 2, which is also 23. When a human germ cell undergoes meiosis, the two sets of 23 chromosomes are split in half to form gametes.
Gametogenesis, the development of diploid germ cells into either haploid eggs or sperm (respectively oogenesis and spermatogenesis) is different for each species but the general stages are similar.

Western clawed frog

Xenopus tropicalisTropical clawed frogX. tropicalis
For example, species of Xenopus (African toads) form a ploidy series, featuring diploid (X.tropicalis, 2n=20), tetraploid (for example X.laevis, 4n=36), octaploid (for example X.wittei, 8n=72) and dodecaploid (for example X.ruwenzoriensis, 12n=108) species.
The western clawed frog (Xenopus tropicalis) is a species of frog in the family Pipidae, also known as tropical clawed frog. It is the only species in the genus Xenopus to have a diploid genome.

Somatic cell

somatic cellssomaticvegetative cell
Somatic cells, tissues and individuals can be described according to the number of sets present (the ploidy level): monoploid (1 set), diploid (2 sets), triploid (3 sets), tetraploid (4 sets), pentaploid (5 sets), hexaploid (6 sets), heptaploid or septaploid (7 sets), etc. The generic term polyploid is used to describe cells with three or more chromosome sets.
If a somatic cell contains chromosomes arranged in pairs, it is called diploid and the organism is called a diploid organism.

Endoreduplication

endoreplicationendomitotic
However, in many situations somatic cells double their copy number by means of endoreduplication as an aspect of cellular differentiation.
Cell ploidy often correlates with cell size, and in some instances, disruption of endoreplication results in diminished cell and tissue size suggesting that endoreplication may serve as a mechanism for tissue growth.

Banana

bananasbanana treebanana flower
While the original wild bananas contained large seeds, diploid or polyploid cultivars (some being hybrids) with tiny seeds are preferred for human raw fruit consumption.

Gene

genesnumber of genesgene sequence
Ploidy is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes.
In sexually reproducing organisms, a specialized form of cell division called meiosis produces cells called gametes or germ cells that are haploid, or contain only one copy of each gene.

Haplodiploidy

haplodiploidhaplodiploid sex-determination systemhaplo-diploid
In humans, only the gametes are haploid, but in the Australian bulldog ant, Myrmecia pilosula, a haplodiploid species, haploid individuals of this species have a single chromosome, and diploid individuals have two chromosomes.
Haplodiploidy is a sex-determination system in which males develop from unfertilized eggs and are haploid, and females develop from fertilized eggs and are diploid.

Biological life cycle

life cyclelife historylifecycle
Ploidy can also differ with life cycle.
Life cycles that include sexual reproduction involve alternating haploid (n) and diploid (2n) stages, i.e., a change of ploidy is involved.

Plant

plantsfloraplant kingdom
Tetraploidy (four sets of chromosomes, 2n = 4x) is common in plants, and also occurs in amphibians, reptiles, and insects. All plants and many fungi and algae switch between a haploid and a diploid state, with one of the stages emphasized over the other.
This involves an alternation between two generations: a haploid stage, called the gametophyte, and a diploid stage, called the sporophyte.

Alternation of generations

alternation of generationalternatingdiplohaplontic
Alternation of generations occurs in many plants.
In these groups, a multicellular gametophyte, which is haploid with n chromosomes, alternates with a multicellular sporophyte, which is diploid with 2n chromosomes, made up of n pairs.

Eukaryote

eukaryoticeukaryotesEukaryota
The nucleus of a eukaryotic cell is haploid if it has a single set of chromosomes, each one not being part of a pair.
In meiosis, DNA replication is followed by two rounds of cell division to produce four haploid daughter cells.

Egg cell

ovumovaegg
Gametes (sperm and ova) are haploid cells.
When egg and sperm fuse, a diploid cell (the zygote) is formed, which rapidly grows into a new organism.

Moss

mossesBryophytafirst terrestrial plants
Most fungi and algae are haploid during the principal stage of their lifecycle, as are plants like mosses.
Mosses used to be grouped together with the hornworts and liverworts as "non-vascular" plants in the former division "bryophytes", all of them having the haploid gametophyte generation as the dominant phase of the life cycle.

Triploid syndrome

Triploidy
If the fertilization of human gametes results in 3 sets of chromosomes the condition is called triploid syndrome.
Triploidy can result from either two sperm fertilizing one egg (polyspermy) (60%) or from one sperm fertilizing an egg with two copies of every chromosome (40%).

Fungus

fungifungalnecrotrophic
All plants and many fungi and algae switch between a haploid and a diploid state, with one of the stages emphasized over the other.
With plants: Fungi have a cell wall and vacuoles. They reproduce by both sexual and asexual means, and like basal plant groups (such as ferns and mosses) produce spores. Similar to mosses and algae, fungi typically have haploid nuclei.