The goal of mitosis is to create two identical cells from the original. Same exact DNA and all the same organelles in each daughter cell The cells has to duplicate its genetic material and then those copies separate into two new nuclei. The goal of meiosis is to make four different cells with half the number of chromosomes. In meiosis things start the same way. A cell has to duplicate its chromosomes, but from here there are some differences. During prophase the homologous pair swap sections of their chromosomes creating more variation in the genes. The homologous pairs split up in the first division but in the second division the chromatids separate into single chromosomes This give four totally different cells with half the normal number of chromosomes But why would we want any cells with half the number of chromosomes? Sex - oh sure, now you're paying attention But seriously, in order for the sperm of the father and the egg of the mother to make a normal baby, they each have to contribute half of the chromosomes The sperm and the egg are haploid, which means that they have half the normal amount of chromosomes To show the haploid number we show the letter n In the case of humans the sperm has 23 chromosomes and the egg has 23 chromosomes And when they come together we create a zygote with 46 chromosomes This is 2n, because n + n is 2n The new zygote is diploid. It has the normal amount of chromosomes Different animals and plants will have different diploid numbers for their species For example, fruit flies have 8 chromosomes Dogs have 78 and lilies have 24 All of the somatic cells in your body are diploid Somatic cells are all of the cells in your body except the sex cells or gametes Those are haploid. The only sex cells are sperm and egg Males make sperm in the testes and females make eggs in the ovaries Males make sperm continually from puberty, but females are born with all of their eggs in the ovaries and only begin to release eggs after puberty. Its kind of a strange thought to realize that half of your DNA was around in your mother for years and years before that egg was finally released, fertilized, and became you. It's pretty amazing Thanks for watching this episode of Teacher's Pet Please remember to like and subscribe and follow me on twitter at sciencepet.