Meiosis and MutationsMeiosis and Mutations

Remember:Remember:MitosisMitosis - takes place in regular - takes place in regular

body cells (somatic cells)body cells (somatic cells) and you and you end up with end up with 2 identical diploid 2 identical diploid (2n) (2n) cells where “n” = the # of cells where “n” = the # of chromosomes.chromosomes.

MeiosisMeiosis

MeiosisMeiosis - takes place in - takes place in sex sex cells (gametes)cells (gametes) and you end up and you end up with with four haploid (n) cells four haploid (n) cells b/c b/c there are there are 2 divisions 2 divisions (Meiosis I (Meiosis I & II)& II)

– Female = eggFemale = egg– Male = spermMale = sperm

Prophase I: Crossing over occurs between replicated homologous chromosomes

Crossing over(exchanging parts)

Note: “X’s” are next to each other, not above each other

Metaphase I: Replicated chromosomes get next to each other in the cell

Anaphase I: homologous chromosomes separate

Telophase I: replicated chromosomes still need to be separated

still looks like an “X”

Now Meiosis II occurs (looks like mitosis)

In males this meiosis is called In males this meiosis is called spermatogenesisspermatogenesis (“sperm (“sperm creation”)creation”)

In females this meiosis is In females this meiosis is called oogenesiscalled oogenesis (“egg (“egg creation”)creation”)

Of the four cells produced in oogenesis, Of the four cells produced in oogenesis, only one will develop into a fully functional only one will develop into a fully functional egg. The other 3 lack the cytoplasm for egg. The other 3 lack the cytoplasm for development and are called polar bodiesdevelopment and are called polar bodies

Sperm (n) from the male fertilizes Sperm (n) from the male fertilizes Egg (n) from the female and a Egg (n) from the female and a zygote (2n) is formedzygote (2n) is formed

There is There is no new genetic no new genetic information introduced in information introduced in MitosisMitosis– everything is identicaleverything is identical

What about Meiosis?What about Meiosis?– YES, YES, NEW genetic information NEW genetic information is introducedis introduced! Genetic ! Genetic variation makes us all look variation makes us all look different!different!

– ½ from mom & ½ from dad½ from mom & ½ from dad