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Gametes

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In sexual reproduction, the union of two parents of different sex occurs, one male and the other female. Each one will contribute a quota of genetic information to their descendants for which they will be similar to their precursors, but not the same. They are in charge of carrying the genetic information that determines the physical characteristics of the new being. Do you want to know what role gametes play in the whole process? Keep reading and you know it.

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What are gametes?

Gametes are reproductive cells made up of a single set of chromosomes that – at the time of fertilization – fuse with another gamete to create a zygote. They are haploid, that is, they only contain half the total number of chromosomes, in such a way that when the union between two occurs, the regulatory number of chromosomes is restored, and it becomes diploid.

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  • Gamete characteristics
  • Gamete types
  • Training
  • Where are they produced?
  • How do they originate?
  • Fertilization
  • Disparity
  • Function
  • Gametes of plants
  • Type of reproduction in which gametes intervene
  • Importance

Gamete characteristics

The female gametes have three prominent parts:

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  • Zona pellucida : It is a crystalline covering that surrounds the ovary providing protection.
  • Radiated crown: It is a mantle of follicles externally attached to the zona pellucida, it disappears with fertility.
  • Cortical granules: These have enzymes that make it impossible for another sperm to enter when fertilization occurs.

In terms of size, it is 500 times larger than sperm and is immobile. There are about 2 million for each ovary at birth, and they can live up to 48 hours.

Male gametes or sperm have three prominent areas:

  • Head: Where the paternal DNA is kept.
  • Middle segment : Here are the mitochondria.
  • Tail: This is the one that allows mobility.

It is quite miniscule in size, it can move, there are around 20 million / ml, and it can live up to 72 hours.

Gamete types

In general, the species cause two types of morphologically dissimilar gametes . A subject produces only one type, as is the case with the female and male gametes.

  • Female: In animals, the female gamete is called an ovum. Its name in plants is oosphere.
  • Male: As sperm, the male gamete is known in animals. In plants the male gamete that fertilizes the oosphere is known as pollen.

Training

Human beings, like most animals, are multicellular organisms that multiply their species through a type of reproduction known as sexual. This is intended to create subjects with genetic characteristics originating in two people, which gives species a much greater versatility than asexual reproduction offers.

For sexual reproduction to produce a new being, it will be necessary for a certain type of cell to fuse: sex cells or gametes . These are produced by multicellular organisms, mainly animals and plants, to carry out reproduction.

This process of gamete formation is called gametogenesis. They are created inside the sexual glands in order to merge in the fertilization phase, thus achieving the reproduction of the human being. The female gamete when fused with the male gamete gives rise to the zygote.

Where are they produced?

The organ where the gametes of animals are produced is the gonad , and in plant bodies it is called gametangia. The formation of female gametes occurs in the ovaries and is known as oogenesis. It begins in the intrauterine stage and resumes at puberty, due to the effect of hormonal action. It is a cyclical and discontinuous procedure that concludes in adulthood.

The process of creation of male gametes has its origin in the testes, specifically in the seminiferous tubules and is known as spermatogenesis. It begins at puberty as a result of hormonal action. It is an ongoing process that ends in adulthood.

How do they originate?

Gametes are formed from germ cells , through inherent cell division known as meiosis , providing half of the genetic duplicates that the stem cell possesses.

Fertilization

It is the process where two sex cells or gametes fuse and form a diploid zygote that will generate a new individual. Fertilization performs two significant functions: It allows the transfer of genes from parents to children, and it releases a group of metabolic reactions in the egg that will initiate the process that leads to embryonic progress. Although this process is not the same between one species and another, there are common events such as:

  • Union and recognition between gametes, entry of sperm, interaction with the extracellular coatings of the oocyte and initiation of the acrosome reaction.
  • Entry of the sperm, penetration of the ovule covers, there is melting of membranes, depolarization of the ovule membrane and cortical reaction, blocking polyspermia.
  • Fusion of the genetic material of one cell and the other, regenerating an efficient diploid genome.
  • Acceleration of egg metabolism, development through nascent mitotic partitions, and expression of maternal genes.

Disparity

In some species the gametes are morphologically and physiologically the same. However, there can be a certain genetic difference . Evolutionary scholars have noted a clear propensity for a female gamete to become increasingly differentiated from a male one. The female gamete tends to be large and immobile and the male gamete is smaller and moves.

Function

Gametes, as already mentioned, are produced in the gonads . They are the protagonists of fertilization. They make possible animal reproduction, as well as the preservation of species. The male gamete fertilizes the ovum and thus provides the complementary genetic information to the female gamete and in this way passes the genetic information of the parents.

Gametes of plants

Plants, like animals, have a reproductive organism, although a little different. The gamete of female plants is known as the oosphere, and is similar to the ovule of animals. In males it is named pollen, being similar to sperm in animals.

The oosphere

The oosphere is known as the type of female sexual cell in plants , which have the potential to reproduce sexually. This type of cell is found within the aforementioned seminal rudiments that are located in the embryo sacs of plants, in flowers.

Similar to the ovules of animals, they have half the chromosomes of the rest of the cells of the ancestor organism. The pollen or male vegetable gamete will enter into union with it through the stigma of the flowers.

The pollen

Pollen is the plant equivalent of sperm : the male sex cell in plants. They are a representation of small grain-shaped particles that are constituted in the stamens of plants. It joins the oosphere in a step called pollination , for which the help of the wind or certain animals is necessary.

These particles also only have half of the fundamental genetic information for a new being to be produced. Pollen enters the stigma and binds to the oosphere. To do this, once located in the stigma, the pollen creates a small limb called the pollen tube that aims to transfer its genetic material to the oosphere.

Type of reproduction in which gametes intervene

Two types of reproduction are known, sexual and asexual . Gametes only participate in sexual reproduction. Two individuals are involved and the descendants inherit part of the characters from each of their parents.

In general, animal species and certain plant species have one sex and, therefore, cause only one type of gametes, either male or female. In this case, it is said that they are unisexual or of different sex, for example the human species and the snitch.

It should be noted that in other species of plants and some animals, it is the case that the same individual can produce both types of gametes, since it has sexual organs of both. These specimens are known as hermaphrodites, examples of which are the snail and the poppy.

Importance

The importance of gametes or sex cells lies in the fact that they are responsible for the process of fertilization and reproduction of species, both in humans and in plants. Through the union of the egg and the sperm, the first cell will be formed, which will begin to multiply in the maternal womb, forming a new being. Likewise, these new cells contain the absolute genetic information of the species and from it an individual with characteristics identical to its ascendant will be formed.

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