Biology - Ch. 11 - Sexual Reproduction and Meiosis

Diploid somatic (body) cells produce more diploid somatic cells; daughter cells are identical to parent cells.

1. Function: growth and repair; asexal reproduction. 2. Number of division series: one 3. Result: two diploid (2n) cells.

Diploid germ cells produce haploid sex cells (gametes); daughter cells are gentically unique.

1. Function: sexual reproduction 2. Number of division series: Two a. Meiosis I - Reduces chromosome number by half b. Meiosis II - Multiplies the cell number (just like mitosis) 3. Result: Four haploid (n) cells

1. Synapsis: Homologous chromosomes pair up and align point by point. 2. Crossing Over: the process occuring during synapsis, in which homologous chromosomes exchange segments of chromosomes; results in new combos of genes in each chromosome and is one source of genetic variation. stage of meiosis

Homologous chromosomes randomly line up at the spindle equator in a process known as "random assortment"; this is another source of genetic vartiaion. stage of meiosis

Homologous chromosomes (still duplicated) seperate (more to opposite poles) forming two haploid cells each of which has a random mix of maternal and paternal chromosomes (known as "random assortment") stage of meiosis

Results in two haplod cells; no interphase or DNA replication. stage of meiosis

Chromosomes recondense. stage of meiosis

Individual chromosomes line up at the equator. stage of meiosis

The chromatids seperate and are renamed "daughter" chromosomes. stage of meiosis

Results in four haploid cells. stage of meiosis

Sources of genetic variability:

Gamete formation

Meiosis and gamete formation in males.