What Does Reduction Division Mean

Purpose: Meiosis is a special variation of cell department that occurs just in the testes and also ovaries; the organs that produce the male and female refertile cells; the sperm and eggs. Why is this different? Ordinary body cells have a finish set of chromosomes. If body cells from mommy and dad fused to form a baby, the fertilized egg would have actually twice as many chromosomes as it need to. Meiosis is sometimes referred to as "reduction division" because it reduces the number of chromosomes to half the normal number so that, when fusion of sperm and also egg occurs, baby will certainly have the correct number. Thus the function of meiosis is to produce gametes, the sperm and eggs, via fifty percent of the genetic complement of the parent cells. In the figures listed below, pink represents a hereditary contribution from mom and also blue represents a hereditary contribution from dad. In this example, a diploid body cell has 2n = 4 chromosomes, 2 from mother and also 2 from dad. In human beings, 2n = 46, and also n = 23.

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Meiosis I

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Meiosis II


Meiosis I

Interphase I: Identical to Interphase in mitosis.

Prophase I: Identical to Prophase in mitosis.

Metaphase I: Instead of all chromosomes pairing up alengthy the midline of the cell as in mitosis, homologous chromosome pairs line up next to each other. This is dubbed synapsis. Homologous chromosomes contain the matching alleles donated from mom and father. This is likewise once meiotic recombicountry, likewise understand as "crossing over" (see below) occurs. This procedure enables for a genetic shuffling of the attributes of the 2 paleas, developing an practically boundless array of possible combinations. See the close-up diagram below.

Anaphase I: Instead of chromatids separating at the centromere, homologous chromosome pairs (currently shuffled by crossing over) relocate alengthy the spindle fibers to oppowebsite poles.

Telophase I: The cell pinches and divides.

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Meiosis II

Prophase II: It is visibly noticeable that replication has not developed.

Metaphase II: The paired chromosomes line up.

Anaphase II: The chromatids split at the centromere and migrate alengthy the spindle fibers to oppowebsite poles.

Telophase II: The cells pinch in the facility and divide aobtain. The last outcome is four cells, each with half of the hereditary material found in the original. In the situation of males, each cell becomes a sperm. In the instance of females, one cell becomes an egg and the various other three come to be polar bodies which are not provided.


Meiotic Recombination (Crossing over):

Your parents each have at leastern one pair of alleles (versions of a gene) for eextremely trait (and also many pairs of alleles for each polygenic trait). You ended up with half of mom"s paired genes and also half of dad"s paired genes. But each non-identical-twin son of these parents ends up via a various combination. Imagine, for instance, that eye shade was controlled by a single gene, and also that mother could have B, the allele for brvery own eyes or b, the allele for blue eyes, and dad can additionally have actually B or b. This leads to 4 possibilities: You might obtain B from mommy and B from dad, or B from mommy and b from dad, or b from mom and B from dad, or b from mom and b from dad. Each sperm and also egg will end up with either B or b from mom and also either B or b from dad. It"s a flip of the coin. But this happens individually for each trait, so simply because you obtained your dad"s brown eyes doesn"t intend you"ll get his blond hair too. Each sibling is 50% mommy and also 50% dad, yet which 50% of each can differ in the siblings. This shuffling process is recognized as recombicountry or "crossing over" and also occurs while the chromome pairs are lined up in Metaphase I.