How do meiosis i and ii contribute to genetic variation? use the diagram to explain your answer.

Question: How do meiosis i and ii contribute to genetic variation? use the diagram to explain your answer.

Meiosis is a type of cell division that produces gametes, or sex cells, such as sperm and egg. Unlike mitosis, which produces identical copies of the parent cell, meiosis introduces genetic variation in the offspring. This variation is important for evolution and adaptation.

How does meiosis create genetic variation? There are two main mechanisms: crossing over and independent assortment. Both of these occur during the first stage of meiosis, called meiosis I.

Crossing over is the exchange of genetic material between homologous chromosomes, which are pairs of chromosomes that have the same size, shape and genes. During meiosis I, the homologous chromosomes pair up and form a structure called a tetrad. Then, they swap segments of DNA at random points, creating new combinations of alleles (different versions of the same gene). For example, if one chromosome has the alleles A and B, and another has the alleles a and b, crossing over can produce chromosomes with the alleles A and b, or a and B.

Independent assortment is the random distribution of homologous chromosomes to the daughter cells. During meiosis I, the tetrads line up along the middle of the cell and separate randomly, with each daughter cell receiving one chromosome from each pair. This means that each gamete can have a different combination of maternal and paternal chromosomes. For example, if the parent cell has two pairs of chromosomes, AB and ab, the gametes can have either AB or ab, or Ab or aB.

The diagram below illustrates these two processes:

In the diagram, you can see how crossing over occurs in prophase I, when the homologous chromosomes pair up and exchange segments. You can also see how independent assortment occurs in metaphase I, when the tetrads line up randomly and separate.

The second stage of meiosis, called meiosis II, does not introduce any new variation, but it reduces the number of chromosomes by half. This is necessary to maintain a constant number of chromosomes in sexually reproducing organisms. During meiosis II, the sister chromatids (identical copies of each chromosome) separate and go to different daughter cells. The result is four haploid cells (cells with half the number of chromosomes), each with a unique combination of alleles.

Meiosis is therefore a key process that generates genetic diversity in sexual reproduction. By creating new combinations of alleles through crossing over and independent assortment, meiosis increases the variation in the gene pool and allows for adaptation to changing environments.

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