1. Meiosis is Necessary for Sexual Reproduction
3 Sexual Reproduction –
Meiosis I
3 Prophase I –
2 Metaphase I –
2 Anaphase I –
2 Telophase I –
Meiosis II
2 Prophase II –
2 Metaphase II –
2 Anaphase II –
2 Telophase II –
4 The Why and Where of Meiosis -

2. Unit IV
Genetics
LEARNING GOAL 2
RELATE THE PROCESS OF MEIOSIS TO THE
INHERITANCE OF GENETIC TRAITS.

3. Meiosis is Necessary for Sexual
Reproduction
 Sexual Reproduction
Reproductive method of
most plants and animals.
Gametes (sex cells) from
opposite sexes unite to
form a zygote (fertilized
egg).
A zygote is a diploid cell
(full chromosome set) so
the number of
chromosomes in the
gametes must be half
(haploid).
Meiosis results in gamete
production.

5. Meiosis I
Prophase I
Same as prophase of mitosis
except chromosomes form
homologous pairs.
Homologous means that the
chromosomes contain genes for
the same traits and one
member of the pair came from
the mother and one from the
father.
Homologs may exchange
sections of chromosomes at this
stage which is called crossing
over.

6. Metaphase I
 Homologous pairs
move to center of cell.
 Each homolog still
consists of two
chromatids.

7. Anaphase I
 Homologs separate.
 Chromatids of each
homolog stay
together.

8. Telophase I
 Chromosomes gather
at opposite poles of
cell, then cytokinesis
occurs.
 Each cell now has half
the original number of
chromosomes.

9. Meiosis II
Same as mitosis.
Prophase II
Chromosomes are still
doubled and become
visible.

10. Metaphase II
 Replicated chromosomes line up in the middle.

11. Anaphase II
 Sister chromatids are pulled apart at the
centromeres.

12. Telophase II
 Chromosomes gather at opposite poles
 Nuclear membrane reforms
 Cell divides

13. The Why and Where of Meiosis
 Results in the production of
male and female gametes
(sperm and egg).
 Produces haploid cells so that
the diploid number can be
restored upon fusion of
gametes during fertilization.
 Occurs in cells of the
reproductive organs, testes in
males and ovaries in females.
 Creates genetic variation due to
crossing over and shuffling of
homologous chromosome
pairs.