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Human gametes: ovum & spermatozoon. Approximately 50% of the floating sperms contain the y-chromosome (--> fertilization leads to a male ♂ child), the other 50% encompass the x-chromosome (--> conception pruduces a female ♀ child) | by quapan
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Human gametes: ovum & spermatozoon. Approximately 50% of the floating sperms contain the y-chromosome (--> fertilization leads to a male ♂ child), the other 50% encompass the x-chromosome (--> conception pruduces a female ♀ child)

A gamete is a specialized sex cell that fuses with another gamete during fertilization (conception) in organisms that reproduce sexually. Gametes are produced by germ cells.

 

In species which produce two morphologically distinct types of gametes, and in which each individual produces only one type, a female is any individual which produces the larger type of gamete—called an ovum (or egg)—and a male produces the smaller type—called a spermatozoon (or sperm cell).

 

The name gamete was introduced by the Austrian biologist Gregor Mendel.

 

Haploid is the term used when a cell has half the usual number of chromosomes. A normal eukaryote organism is composed of diploid cells, one set of chromosomes from each parent. However, after meiosis, the number of chromosomes in gametes is halved. That is the haploid condition.

 

In humans, the diploid number of chromosomes is 46 (2x23). The number in haploid cells (sperm and eggs) is 23. Some types of animals are haploid, such as male Hymenoptera (ants, bees and wasps). This is a special genetic system called haplodiploidy.

 

Some plants and animals are polyploid, with more than two sets of chromosomes. For example, one species of wheat is hexaploid, with six sets of chromosomes, although other species of wheat have only two sets. Because so many organisms are diploid, it can become confusing whether haploid refers to one set of chromosomes or more than one. The special term monoploid can be used; it means one set of chromosomes.

 

 

Gametogenesis

Gametogenesis is the development of diploid germ cells into haploid eggs or sperm, (respectively oogenesis and spermatogenesis). It is different for each species but the general stages are similar. The development of eggs (oogenesis} and sperm (spermatogenesis) have many features in common. They both involve:

--- Meiosis

--- Extensive morphological cell differentiation

--- Unable to survive for very long if fertilization does not occur

 

They also have major differences, especially

Different timing of maturation: oogenic meiosis is interrupted at one or more stages (for a long time) while spermatogenic meiosis is rapid and uninterrupted.

 

 

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Menschliche Eizelle mit Spermatozoon sich nähernd (maßstabsgetreu)

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Uploaded on August 16, 2016