Meiosis
There are two major differences between mitosis and meiosis. First, meiosis involves not one, but two cell divisions. Second, meiosis leads to the production of germ cells, which are cells that give rise to gametes. Germ cells are different from somatic cells in a critical way. Whereas somatic cells are diploid, meaning they have two copies of each chromosome, germ cells are haploid. The haploid nature of germ cells is vital to the process of sexual reproduction.
There are two different sex cells or gametes: sperm and eggs. Males produce sperm and females produce eggs. Because they are produced from germ cells, gametes are likewise haploid. In order to create a new individual via sexual reproduction, a sperm cell needs to activate an egg by joining it in a fertilization process. When these two haploid cells unite, a diploid cell results. This specialized cell can then develop into a new individual. The sexual reproductive process just described ensure that the resulting offspring will have an equal maternal and paternal genetic contribution.
As we mentioned earlier, higher-order cells contain homologous pairs of chromosomes--one from the father and the other from the mother. In meiosis, as in mitosis, the maternal and paternal homologues are replicated during DNA replication yielding two pairs of sister chromatids. After the first cell division, each of the resulting cells contains a pair of sister chromatids—-one maternal pair and the other paternal. Unlike mitosis, meiosis does not end after one division; it continues with a second cell division. In this division, the sister chromatids are separated yielding four total haploid cells.
There are two major differences between mitosis and meiosis. First, meiosis involves not one, but two cell divisions. Second, meiosis leads to the production of germ cells, which are cells that give rise to gametes. Germ cells are different from somatic cells in a critical way. Whereas somatic cells are diploid, meaning they have two copies of each chromosome, germ cells are haploid. The haploid nature of germ cells is vital to the process of sexual reproduction.
There are two different sex cells or gametes: sperm and eggs. Males produce sperm and females produce eggs. Because they are produced from germ cells, gametes are likewise haploid. In order to create a new individual via sexual reproduction, a sperm cell needs to activate an egg by joining it in a fertilization process. When these two haploid cells unite, a diploid cell results. This specialized cell can then develop into a new individual. The sexual reproductive process just described ensure that the resulting offspring will have an equal maternal and paternal genetic contribution.
As we mentioned earlier, higher-order cells contain homologous pairs of chromosomes--one from the father and the other from the mother. In meiosis, as in mitosis, the maternal and paternal homologues are replicated during DNA replication yielding two pairs of sister chromatids. After the first cell division, each of the resulting cells contains a pair of sister chromatids—-one maternal pair and the other paternal. Unlike mitosis, meiosis does not end after one division; it continues with a second cell division. In this division, the sister chromatids are separated yielding four total haploid cells.
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