Sexual Reproduction

Meiosis – the formation of sex cells

Vocabulary• Somatic Cell• Gamete• Homologous

Chromosomes• Diploid Cells ( 2n )

• Haploid Cells ( n )

• Normal body cell• Sex cell – sperm or egg• Matching pairs of

chromosomes• Cells that have

homologous chromosomes (somatic cells)

• Cells that have only one chromosome from each pair (gametes)

Which cell is diploid and which is haploid?

Haploid Cell Diploid Cell

Mitosis vs. Meiosis

Mitosis

• Asexual Reproduction• Results in two genetically

identical daughter cells• Creates diploid ( 2n ) cells• Involves one cell division

Meiosis

• Sexual Reproduction• Results in four genetically

different daughter cells• Creates haploid ( n ) cells• Involves two cell divisions

Prophase I

• Homologous chromosomes form a tetrad

• Segments of chromatids are exchanged

Metaphase I

• Tetrads line up at the center of the cell

Anaphase I

• Fibers pull tetrads apart• Haploid chromosomes

move to opposite sides of cell

Telophase

• Two haploid cells are formed

Prophase II

• New fibers form and begin to connect to haploid chromosomes

Metaphase II

• Chromosomes line up along the middle of the cell

Anaphase II

• Chromatids of each chromosome separate and move towards opposite sides of the cells

Telophase II

• Both cells divide to form four haploid cells containing half of the normal chromosome number.

• Haploid cells turn into either sperm or egg cells depending on where they are formed.