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A gamete ( /ˈɡæmiːt/; from
Ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally referred to by speakers simply as Greek (, ), refers collectively to the diale ...
γαμετή ''gamete'' from gamein "to marry") is a haploid cell that fuses with another haploid cell during
fertilization Fertilisation or fertilization (see American and British English spelling differences#-ise.2C -ize .28-isation.2C -ization.29, spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes ...

fertilization
in
organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological me ...

organism
s that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce two morphologically distinct types of gametes, and in which each individual produces only one type, a
female Female (symbol: ♀) is the sex Sex is either of two divisions, typically male Male (♂) is the sex of an organism that produces the gamete known as sperm. A male gamete can fuse with a larger female gamete, or ovum, in the process of ...

female
is any individual that produces the larger type of gamete—called an
ovum The egg cell, or ovum (plural ova), is the female reproductive Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. Reproduct ...

ovum
— and a
male Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilization. A male organism cannot sexual reproduction, reproduce sexually ...

male
produces the smaller type—called a
sperm Sperm is the male reproductive Cell (biology), cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as ...

sperm
. Sperm cells or spermatozoa are small and motile due to the flagellum, a tail-shaped structure that allows the cell to propel and move. In contrast, each egg cell or ovum is relatively large and non-motile. In short a gamete is an egg cell (female gamete) or a sperm (male gamete). In animals, ova mature in the ovaries of females and sperm develop in the testes of males. During fertilization, a spermatozoon and ovum unite to form a new diploid organism. Gametes carry half the
genetic information A nucleic acid sequence is a succession of bases signified by a series of a set of five different letters that indicate the order of nucleotides Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monom ...
of an individual, one
ploidy Ploidy () is the number of complete sets of chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. Most eukaryotic chromosomes include packaging proteins called histones which, aided by ...
of each type, and are created through
meiosis Meiosis (; , because it is a reductional division) is a special type of of in organisms used to produce the , such as or . It involves two rounds of division that ultimately result in four cells with only one copy of each (). Additionall ...

meiosis
, in which a germ cell undergoes two fissions, resulting in the production of four gametes. In biology, the type of gamete an organism produces determines the classification of its sex. This is an example of
anisogamy Anisogamy (also called heterogamyHeterogamy is a term applied to a variety of distinct phenomena in different scientific domains. Usually having to do with some kind of difference, "hetero", in reproduction, "gamy". See below for more specific sen ...

anisogamy
or
heterogamyHeterogamy is a term applied to a variety of distinct phenomena in different scientific domains. Usually having to do with some kind of difference, "hetero", in reproduction, "gamy". See below for more specific senses. Science Reproductive biology I ...
, the condition in which females and males produce gametes of different sizes (this is the case in humans; the human ovum has approximately 100,000 times the volume of a single human sperm cell). In contrast,
isogamy Isogamy is a form of sexual reproduction Sexual reproduction is a type of reproduction that involves a complex Biological life cycle, life cycle in which a gamete (such as a sperm or egg cell) with a single set of chromosomes (haploid) combines ...

isogamy
is the state of gametes from both sexes being the same size and shape, and given arbitrary designators for
mating type Mating types are the microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed ...
. The name gamete was introduced by the German cytologist
Eduard Strasburger Eduard Adolf Strasburger (1 February 1844 – 18 May 1912) was a Polish- German professor and one of the most famous botanist Botany, also called , plant biology or phytology, is the science Science (from the Latin word ''scientia'', ...
. Male and female gametes set the basis for the sexual roles and sexual selection.
Oogenesis Oogenesis, ovogenesis, or oögenesis is the differentiation of the ovum (egg cell) into a cell competent to further develop when fertilized. It is developed from the primary oocyte by maturation. Oogenesis is initiated in the embryonic stage. O ...

Oogenesis
is the process of female gamete formation in animals. This process involves
meiosis Meiosis (; , because it is a reductional division) is a special type of of in organisms used to produce the , such as or . It involves two rounds of division that ultimately result in four cells with only one copy of each (). Additionall ...

meiosis
(including meiotic recombination) occurring in the diploid primary
oocyte An oocyte (, ), oöcyte, ovocyte, or rarely ocyte, is a female gametocyte A gametocyte is a eukaryotic Eukaryotes () are organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any indiv ...
to produce the haploid
ovum The egg cell, or ovum (plural ova), is the female reproductive Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. Reproduct ...
.
Spermatogenesis Spermatogenesis is the process by which haploid Ploidy () is the number of complete sets of chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. Most eukaryotic chromosomes include ...

Spermatogenesis
is the process of male gamete formation in animals. This process also involves meiosis occurring in the diploid primary
spermatocyte Spermatocytes are a type of male gametocyte in animals. They derive from immature germ cells called spermatogonia. They are found in the testis, in a structure known as the seminiferous tubules. There are two types of spermatocytes, primary and se ...
to produce the haploid
spermatozoon A spermatozoon (pronounced , alternate spelling spermatozoön; plural spermatozoa; from grc, σπέρμα ("seed") and grc, ζῷον ("living being")) is a motile Motility is the ability of an organism In biology, an organism (from An ...
.


Evolution of gametes

It is generally accepted that
isogamy Isogamy is a form of sexual reproduction Sexual reproduction is a type of reproduction that involves a complex Biological life cycle, life cycle in which a gamete (such as a sperm or egg cell) with a single set of chromosomes (haploid) combines ...

isogamy
is the ancestral state from which anisogamy evolved, although its evolution has left no fossil records.
Oogamy Oogamy is an extreme form of anisogamy Anisogamy (also called heterogamy) is the form of sexual reproduction that involves the union or fusion of two gamete A gamete ( /ˈɡæmiːt/; from Ancient Greek Ancient Greek includes the form ...
also evolved from isogamy through anisogamy. There are almost invariably only two gamete types, all analyses showing that intermediate gamete sizes are eliminated due to selection. Intermediate sized gametes do not have same advantages as small or large ones; they do worse than small ones in mobility and numbers, and worse than large ones in supply.


Dissimilarity

In contrast to a gamete, a diploid
somatic cell A somatic cell (from Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following period ...
of an individual contains one copy of the
chromosome A chromosome is a long DNA Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A mole ...

chromosome
set from the sperm and one copy of the chromosome set from the egg cell. Consequently, the cells of the offspring have genes potentially capable of expressing characteristics of both the ''father'' and the ''mother'', subject to whether they are dominant or recessive. A gamete's chromosomes are not exact duplicates of either of the sets of chromosomes carried in the diploid chromosomes but a mixture of the two.


Sex determination in mammals and birds

Humans Humans (''Homo sapiens'') are the most populous and widespread species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species ...
and most mammals use the
XY sex-determination system The XY sex-determination system is a sex-determination system A sex-determination system is a biological system that determines the development of sexual characteristics in an organism In biology, an organism (from Ancient Greek, Gree ...
in which a normal ovum can carry only an
X chromosome The X chromosome is one of the two sex-determining chromosome A chromosome is a long DNA Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecul ...

X chromosome
whereas a sperm may carry either an X or a Y, while a non-normal sperm cell can end up carrying either no sex-defining chromosomes, an XY pair, or an XX pair; thus the male sperm determines the
sex Sex is either of two divisions, typically male Male (♂) is the sex of an organism that produces the gamete known as sperm. A male gamete can fuse with a larger female gamete, or ovum, in the process of fertilization. A male cannot sexual r ...
of any resulting
zygote A zygote (, ) is a eukaryotic Eukaryotes () are organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are ...

zygote
. If the zygote has two X chromosomes it will develop into a female, if it has an X and a Y chromosome, it will develop into a male. For birds, the female ovum determines the sex of the offspring, through the
ZW sex-determination system The ZW sex-determination system is a chromosomal system that determines the sex of offspring in bird Birds are a group of warm-blooded vertebrates constituting the class Class or The Class may refer to: Common uses not otherwise c ...
.


Artificial gametes

Artificial gametes, also known as In vitro derived gametes (IVD), stem cell-derived gametes (SCDGs), and In vitro generated gametes (IVG), are gametes derived from
stem cells In multicellular organisms Multicellular organisms are organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies the Life#Biology, properties o ...
. Research shows that artificial gametes may be a reproductive technique for same-sex male couples, although a
surrogate mother Surrogacy is an arrangement, often supported by a legal agreement, whereby a woman (the surrogate mother) agrees to bear a child for another person or persons, who will become the child's parent(s) after birth. People may seek a surrogacy arr ...
would still be required for the gestation period. Women who have passed
menopause Menopause, also known as the climacteric, is the time in women's lives when menstrual periods stop permanently, and they are no longer able to bear children. Menopause usually occurs between the age of 48 and 52. Medical professionals often ...
may be able to produce eggs and bear genetically related children with artificial gametes. Robert Sparrow wrote, in the
Journal of Medical Ethics The ''Journal of Medical Ethics'' is a monthly peer-reviewed Peer review is the evaluation of work by one or more people with similar competencies as the producers of the work ( peers). It functions as a form of self-regulation by qualified m ...
, that embryos derived from artificial gametes could be used to derive new gametes and this process could be repeated to create multiple human generations in the laboratory. This technique could be used to create
cell lines An immortalised cell line is a population of cells from a multicellular organism Multicellular organisms are organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguo ...

cell lines
for medical applications and for studying the heredity of
genetic disorder A genetic disorder is a health problem caused by one or more abnormalities in the genome In the fields of molecular biology and genetics, a genome is all genetic information of an organism. It consists of nucleotide sequences of DNA ( ...
s. Additionally, this technique could be used for
human enhancement Human enhancement (HE) can be described as the natural, artificial, or technological Technology ("science of craft", from Ancient Greek, Greek , ''techne'', "art, skill, cunning of hand"; and , ''wikt:-logia, -logia'') is the sum of Art techn ...
by
selectively breeding This Chihuahua mix and Great Dane shows the wide range of dog breed sizes created using selective breeding. Selective breeding (also called artificial selection) is the process by which humans use animal breeding Animal breeding is a branc ...
for a desired genome or by using
recombinant DNA Recombinant DNA (rDNA) molecules are DNA Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings ...

recombinant DNA
technology to create enhancements that have not arisen in nature.


Plants

Plants Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel t ...

Plants
which reproduce sexually also produce gametes. However, since plants have a life cycle involving some differences exist. Plants use
meiosis Meiosis (; , because it is a reductional division) is a special type of of in organisms used to produce the , such as or . It involves two rounds of division that ultimately result in four cells with only one copy of each (). Additionall ...

meiosis
to produce spores that develop into
multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy (biolo ...
haploid
gametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all ...
s which produce gametes by mitosis. The sperm are formed in an organ known as the
antheridium An antheridium is a haploid Ploidy () is the number of complete sets of chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. Most eukaryotic chromosomes include packaging proteins call ...

antheridium
and the egg cells in a flask-shaped organ called the
archegonium 240px, Diagram of archegonium anatomy An archegonium (pl: archegonia), from the ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 3 ...

archegonium
. In
flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greec ...

flowering plant
s, the female gametophyte is produced inside the
ovule In seed plant The spermatophytes, also known as phanerogams (taxon Phanerogamae) or phaenogams (taxon Phaenogamae), comprise those plants that produce seeds, hence the alternative name seed plants. They are a subset of the embryophytes or l ...

ovule
within the
ovary The ovary is an organ found in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the b ...
of the flower. When mature, the haploid gametophyte produces female gametes which are ready for fertilization. The male gametophyte is produced inside a
pollen Pollen is a powdery substance consisting of pollen grains which are Sporophyte, microsporophytes of spermatophyta, seed plants, which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the ga ...

pollen
grain within the
anther The stamen (plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical category of number. The plural of a noun typically denotes a quantity greate ...
. When a pollen grain lands on a mature
stigma Stigma or plural stigmata, stigmas may refer to: * Social stigma, the disapproval of a person based on physical or behavioral characteristics that distinguish them from others Symbolism * Stigmata, bodily marks or wounds resembling the crucifix ...
of a flower it germinates to form a
pollen tube A pollen tube is a tubular structure produced by the male gametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (bio ...
that grows down the style into the ovary of the flower and then into the ovule. The pollen then produces sperm by mitosis and releases them for fertilization.


Notes and references

{{Authority control Classical genetics Germ cells Reproductive system