Mitosis and Meiosis

• Cell division is the process of an existing cell forming two new cells.
• New cells created are called daughter cells.
• The division of cells leads to an increase in cell numbers.
• Reproduction of one-celled organisms such as amoeba involves the parent cell dividing into two cells.
• One parent is required, that isn't sperm (sex cells) or ova
• The resulting offspring are two identical daughter cells.

Meiosis

• Meiotic division is cell division that produces genetically different cells.
• In mammals, this occurs in specialized cells in testes and ovaries, producing sex cells with 23 chromosomes.
• Reproduction involving sex cells is sexual reproduction.
• Sexual reproduction involves fertilization.
• Fertilization is the fusion of a sperm with an ovum (egg cell).
• A fertilized egg cell is called a zygote.
• Genetic information from both parents (sperm and ovum) are combined in to a zygote through meiotic division and fertilization

Zygotes

• As a zygote divides, genetic information from both parents passes to a ball of cells, eventually forming a child, which is inherited.
• Organisms that reproduce sexually are like but not identical to their parents, except identical twins.
• Each sperm and ovum produced by the parents is genetically different.
• Crossing over during meiotic division leads to genetically different sex cells.
• Crossing over is when a chromosome from the father and the same chromosome from the mother pair up and exchange lengths of DNA (genes).
• Crossing over happens at random resulting in different combinations of genes on the chromosomes of the father and mother
• Genetically different sex cells leads to increased variation of a species, as does the process of fertilization.
• Which sperm and ovum are involved is random, therefore genetic information passed to offspring is completely random.