Standard 2.7 Describe how the process of meiosis results in the formation of haploid cells. Explain the importance of this process in sexual reproduction, and how gametes form diploid zygotes in the process of fertilization.
Vocabulary
Tier 3
Meiosis - cell division that cuts the chromosome number in half (23) in humans
Haploid - a cell having half the number of chromosomes (sperm and egg)
Diploid - a cell having the FULL number of chromosomes (46) in humans
Gamete - sex cells
sperm - male sex cell (23 chromosomes)
egg - female sex cell (23 chromosomes)
Fertilization - when gametes meet they form a new organisms 23 + 23 = 46
Sexual Reproduction - reproduction using gametes (males and females)
Asexual Reproduction - how bacteria reproduce, with no sperm or egg. (Cloning)
Crossing Over - when homologous chromosomes swap pieces of chromosomes with each other during meiosis
MEIOSIS
Sex cells (sperm and egg) only reproduce by meiosis because they need to cut the chromosome number in half. So for humans 46 chromosomes goes to 23. Sex cells with half the number of chromosomes are called GAMETES.
When a cell has the original number of chromosomes they are called DIPLOID. The human diploid number is 46. Gametes are called HAPLOID. They have half the number of chromosomes.
Crossing Over
Sometimes the chromosomes overlap and swap genes with each other. This is good!! It creates new combinations of genes and helps a species evolve!!