Inheritance

The Body Forms 2 Types of Cells: 1. somatic cells, or body cells, have 2 of each kind of chromosome (a pair) the pair of chromosomes are called homologous because they carry the same traits these cells are diploid (2n)

2. sex cells, or gametes, have only one of each chromosome these cells are haploid (n)

There are 2 Types of Cell Division: mitosis produces somatic cells 2 daughter cells are identical to parent all cells are diploid takes place in most body cells needed for growth and repair

meiosis produces sex cells parent cell divides 2 times produces 4 unique daughter cells daughter cells are haploid

meiosis, cont. takes place in only 2 organs: in females (♀), eggs are produced in the ovaries (oogenesis) in males (♂), sperm are produced in the testes (spermatogenesis)

sexual reproduction involves the production and fusion of sex cells when a sperm fertilizes an egg, a zygote is formed

Stages of Meiosis Interphase cell is growing DNA replicates

Meiosis I Prophase I homologous chromosomes pair up (synapsis) and form a tetrad sometimes non-sister chromatids exchange genetic information during crossing over

crossing over increases genetic variation

Meiosis I Metaphase I tetrads line up

Meiosis I Anaphase I homologous pairs are split up

Meiosis I Telophase I/ Cytokinesis 2 haploid nuclei are formed 2 daughter cells still contain sister chromatids Interkinesis break period between the 2 divisions

Meiosis II Prophase II a new spindle forms

Meiosis II Metaphase II each chromosome lines up at the midline of the cell

Meiosis II Anaphase II the sister chromatids are separated and move to opposite ends of cell

Meiosis II Telophase II two new nuclei are formed each nucleus contains a haploid(n) number of chromosomes Cytokinesis the end result of meiosis is 4 haploid daughter cells