Meiosis

Objectives:

1. Define the term gamete.
2. Describe the process of crossing-over.
3. Summarize the events of meiosis.

Vocabulary:

Gamete – A reproductive cell, an egg or a sperm.

Meiosis – A two stage form of nuclear division occurring with gametes.

Crossing-over – The exchanging of segments of DNA between chromosomes.

• The cell division of gametes (sex cells)
• Two-steps of division
• Results in haploid (n) cells, eggs or sperm
• Starts with 1 diploid cell, ends with 4 haploid cells.

• Crossing-over occurs during meiosis
• When pairs of chromosomes are held close together, the chromosomes exchange segments of DNA
• Results in a new combination of genes in a gamete
• Crossing-over explains genetic variation of offspring, in other words explains why sisters or brothers with the same parents can have very different traits