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Biology 2nd Baccalaureate

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8.2.3. Meiosis and sexual reproduction

Meiosis and sexual reproduction

The genetic recombination of meiosis occurs randomly. For this reason, sexual reproduction is the reproductive mechanism, genetically selected, that most organisms use to ensure that their descendants have a genetic material that is somewhat different from that of their parents.

Remember: in meiosis, four haploid cells are obtained from one diploid stem cell. In meiosis I, whole chromosomes are separated (chromosome reduction occurs), and in meiosis II the chromatids of each chromosome are separated. The daughter cells of the first division, although with duplicated chromosomes, are already haploid.

As a result of meiosis, and gene recombination, each ovule contains genes from the maternal grandfather and grandmother, and sperm cell contains, in turn, genes from the paternal grandfather and grandmother. 

The basic mechanisms that allow the genetic diversity of populations are:

Thus, the genes of a population are scattered among the components of that population. Each individual has characteristics that allow them to adapt better or worse to the environment. As the possible gene combinations are highly variable, when an unfavorable change occurs in the environment, it is possible that some individuals manifest some character that allows them to adapt to that situation, to survive, and to allow the continuity of the species.


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Biology and Geology teaching materials for Compulsory Secondary Education (ESO) and Baccalaureate students.