Purpose: Meiosis is a special version of cell department that occurs only in the testes and also ovaries; the guts that create the male and female reproductive cells; the sperm and also eggs. Why is this different? plain body cells have actually a complete set of chromosomes. If human body cells from mom and dad unify to type a baby, the fertilized egg would have actually twice as many chromosomes together it should. Meiosis is sometimes dubbed "reduction division" because it to reduce the number of chromosomes to fifty percent the common number for this reason that, when fusion of sperm and egg occurs, baby will have actually the exactly number. Because of this the objective of meiosis is to develop gametes, the sperm and also eggs, with fifty percent of the genetic complement of the parental cells. In the figures below, pink represents a genetic contribution native mom and also blue represents a genetic contribution from dad. In this example, a diploid body cell contains 2n = 4 chromosomes, 2 native mom and two indigenous dad. In humans, 2n = 46, and n = 23.

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Meiosis I


Meiosis II

Meiosis I

Interphase I: similar to Interphase in mitosis.

Prophase I: the same to Prophase in mitosis.

Metaphase I: instead of every chromosomes pairing up follow me the midline that the cell as in mitosis, homologous chromosome pairs line up beside each other. This is referred to as synapsis. Homologous chromosomes save the corresponding alleles donated native mother and father. This is also when meiotic recombination, likewise know together "crossing over" (see below) occurs. This process allows for a genetic shuffling that the attributes of the 2 parents, producing an virtually infinite range of feasible combinations. See the close-up diagram below.

Anaphase I: instead of chromatids splitting at the centromere, homologous chromosome pairs (now shuffled by cross over) move along the spindle fibers to the opposite poles.

Telophase I: The cabinet pinches and divides.

Meiosis II

Prophase II: it is visibly noticeable that replication has actually not occurred.

Metaphase II: The paired chromosomes line up.

Anaphase II: The chromatids separation at the centromere and also migrate along the spindle yarn to the opposite poles.

Telophase II: The cell pinch in the center and also divide again. The final outcome is four cells, every with half of the hereditary material uncovered in the original. In the situation of males, every cell i do not care a sperm. In the instance of females, one cabinet becomes an egg and also the other three become polar bodies which space not used.

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Meiotic Recombination (Crossing over):

Your parental each have actually at the very least one pair that alleles (versions of a gene) for every trait (and plenty of pairs that alleles for each polygenic trait). You ended up with fifty percent of mom"s paired genes and fifty percent of dad"s paired genes. Yet each non-identical-twin child of this parents end up v a different combination. Imagine, because that example, that eye shade was managed by a single gene, and that mom might have B, the allele for brown eyes or b, the allele because that blue eyes, and also dad could also have B or b. This leader to 4 possibilities: You could get B from mom and also B from dad, or B indigenous mom and b native dad, or b indigenous mom and B native dad, or b indigenous mom and also b native dad. Each sperm and egg will end up through either B or b native mom and also either B or b indigenous dad. It"s a upper and lower reversal of the coin. Yet this happens independently for every trait, for this reason just due to the fact that you gained your dad"s brown eyes doesn"t median you"ll get his blond hair too. Each sibling is 50% mom and 50% dad, however which 50% that each have the right to vary in the siblings. This shuffling procedure is known as recombination or "crossing over" and occurs if the chromome pairs room lined increase in Metaphase I.