Sexual Reproduction Involves the fusion of nuclear material from two cells called gametes (sperm and egg)

Meiosis is a special type of cell division by which the gametes (sperm and egg) are produced

Production of sperm is called spermatogenesis and occurs in the testes

Production of egg cells is called oogenesis and occurs in the ovaries

Meiosis is necessary for sexual reproduction to occur because it reduces the number of chromosomes before fertilization takes place Because of meiosis, the gametes have half the normal number of chromosomes (haploid)

The stages of meiosis are similar to mitosis but there are 2 cell divisions in meiosis and one in mitosis

Meiosis(Spermatogenesis) In spermatogenesis cell division is equal and results in the production of 4 equal sized sperm cells with flagella

Meiosis (oogenesis) In oogenesis cell division is unequal, resulting in 1 large egg cell and 3 non functional polar bodies

Terms Homologous chromosomes: a pair of chromosomes that have the same size and shape and carry the same type of genetic information One in the pair came from the male and one from the female

Human chromosomes arranged in homologous pairs

Terms Synapsis- during meiosis homologous chromosomes join together to form tetrads tetrads- group of 4 chromotids

Terms Crossing over- during synapsis the chromosomes wrap around each other and exchange segments( genetic information)

Crossing Over

Importance of Meiosis The production of sperm and egg cells that have half the normal number of chromosomes

Importance of Meiosis Meiosis allows for variations

Variations Variations in offspring may occur due to the random way in which the chromosomes line up during meiosis

Variations Variations may occur due to crossing over