Cell DivisionCell Division

By: T. Bolles, Based in Part by “Meiosis.ppt” by K. Ingemunson

MITOSIS• Chromosomes within the cell

make copies of themselves

• The cell divides into 2 cells – 1 is a clone of the other

• These are DIPLOID cells (chromosomes occur in pairs)

MITOSIS

MEIOSIS• The cell divides without

copying chromosomes

• End up with 4 cells, each of these cells has only ½ the normal number of chromosomes

• These cells are called Haploid

MEIOSIS

Meiosis I

Meiosis II

MEIOSIS

Diploid Cells• All cells in the

body except sex cells are diploid.

Haploid Cells• All cells in the

body except sex cells are diploid.

Fertilization• BODY CELL: full

number of chromosomes (two copies = diploid)

• SEX CELL: half the number of chromosomes (one copy = haploid)

• FERTILIZATION: we get genes from each of our parents

Female Sex Cell

Male Sex Cell

Why is Haploids? • If diploid cells are fertilized…

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Chromosome will keep doubling!!

2N + 2N 4N

Why is Haploids?

If haploid cells are fertilized…

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Like all cells of the body!!

N + N 2N

Sexual Reproduction• Reproductive process in which haploid

sex cells (gametes) fuse to produce a diploid fertilized egg (zygote)

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