Meiosis Review and Differentiation

Meiosis is the process that forms gametes. Review: Meiosis is the process that forms gametes. Gametes are sex cells (sperm for males and egg for females) Gametes contain half the number of chromosomes than a body cell. There are no homologous pairs in gametes. (23 chromosomes in humans) Egg meets Sperm

Fertilization- when the sperm and egg come together Chromosome pairs return at fertilization Sperm + Egg  Fertilized Egg (23) + (23) (46) Only one sperm can fertilize an egg 2 nuclei in a Fertilized Egg

Immediately after fertilization: A hard shell covering forms over the zygote

Zygote- name for a fertilized egg The zygote or fertilized egg will begin to divide into many cells. What process is happening in the zygote and why?

Mitosis begins and the zygote begins to grow into a ball of cells. The cells will all have the total number of chromosomes (46 in humans) Day 3 Day 4

Drawing of Fertilized Egg

Cleavage is the splitting of the zygote into many identical cells. Zygote 2 cell 4 cell 8 cell 30 cell

Migration The movement of cells The solid ball becomes almost empty Forms a hollow ball of cells

The blastocyst Hollow ball of cells containing the inner cell mass

The inner cell mass will become the baby The outer cells will help the baby attach to the inside of its mother. www.health.state.mn.us/ wrtk/handbook.html

Human hatching The embryo will “crawl” out of the shell

Review

Implantation The outer cells of the blastocyst will form “roots” and attach to the inside of the mother’s uterus