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Meiosis & Genetic Variability
Next Generation: HS.LS3.2 HS.LS3.2

Meiosis & Genetic Variability

Description:

This lesson will discuss how the process of meiosis produce individuals with varied combinations and variations of parental genes.

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Tutorial

What's Covered

This lesson will look at how meiosis creates new combinations of genes by examining:

  1. Spermatogenesis
  2. Oogenesis
  3. Genetic Variability

1. Spermatogenesis

Meiosis is the cell division that occurs in sex cells. The goal of meiosis is to reduce the parental number of chromosomes by half, making a haploid cell. This is important for when the sperm cells and the egg cells combine; they will produce a diploid cell.

Term to Know

    • Meiosis
    • A type of cell division that takes place in germ cells to produce haploid gametes.

Spermatogenesis is meiosis in sperm cells, and it produces four daughter cells. After a germ cell goes through the process of meiosis I and meiosis II, it will produce four haploid male gametes or sperm cells. Disjunction occurs in meiosis II when homologous chromosomes are separated so that gametes can receive a haploid set of chromosomes.

Term to Know

    • Disjunction
    • Occurs in meiosis II when homologous chromosomes are separated resulting in gametes with a haploid number of chromosomes.

Oogenesis (2).png


2. Oogenesis

Oogenesis is meiosis that occurs in the female egg cells. It will go through two rounds of cell division as well, and result in an egg cell that is haploid. Oogenesis is different from spermatogenesis in that it results in one egg cell, or one ovum, which is haploid and also something called a polar body. In meiosis I the first polar body is formed, and in meiosis II a second polar body is formed. These polar bodies will disintegrate later. They just contain extra genetic information.

Oogenesis.png


3. Genetic Variability

There's two main ways in which meiosis produces genetic variability. The first way is with crossing over. Chromosomes will end up swapping genetic information during meiosis. It is important to note that this does not happen during mitosis. A portion of a chromosome will switch places with another chromosome. It allows for more combinations of genes and more variations.

Term to Know

    • Crossing Over
    • A process in which homologous chromosomes will exchange genetic material with one another; results in genetic variability.

Meiosis also produces genetic variability by the random sorting of chromosomes. Chromosomes are sorted into gametes randomly. By being sorted into gametes randomly, it produces a wide range of combinations of those gametes. Meiosis will not result in gametes that are exactly the same because of this random sorting.

Summary

Meiosis is the cell division that results in gametes. Spermatogenesis is meiosis in sperm cells, and produces four daughter cells. Oogenesis is meiosis that produces a female egg cell. It also produces two polar bodies. Meiosis creates genetic variability in two different ways. Crossing over is where chromosomes will swap portions of genetic information. The other is through the random sorting of chromosomes into gametes.

Keep up the learning and have a great day!

Source: SOURCE: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR AMANDA SODERLIND

TERMS TO KNOW
  • Disjunction

    Occurs in meiosis II when homologous chromosomes are separated resulting in gametes with a haploid number of chromosomes.

  • Crossing Over

    A process in which homologous chromosomes will exchange genetic material with one another; results in genetic variability.

  • Meiosis

    A type of cell division that takes place in germ cells to produce haploid gametes.