1. CELL REPRODUCTION
MEIOSIS

2. Lesson Objectives –Meiosis
Describe asexual reproduction; explain the genetic relationship between parent and offspring.
Describe sexual reproduction; explain the genetic relationship between parent and offspring.
Describe gametogenesis and identify the key differences between oogenesis and spermatogenesis.
Identify and describe the main steps of meiosis, distinguishing between the quantity of genetic material in the parent and resulting cells.

3. ASEXUAL REPRODUCTION One parent
Offspring genetically identical to parent
Does not happen through MEIOSIS!!!
Some modes of reproduction:
Binary fission
Budding
Spore formation

4. SEXUAL REPRODUCTION Two parents
Offspring NOT genetically identical to parents
Happens through MEIOSIS..

5. SEXUAL REPRODUCTION AND GAMETES
Two different cells join together to form a new organism
Gametes (sexual reproduction cells) only have one-half of the chromosomes found in body cells
Two types of gametes
Sperm (male)
Eggs or ova (female)
The union of these two is called fertilization
New diploid cell formed from two haploid cells is called a zygote
Number of chromosomes present in each gamete called haploid number (n)
Number of chromosomes present in each body cell called diploid number (2n)

6. GAMETOGENEIS: SPERMATOGENESIS AND OOGENESIS
Spermatogenesis produces four haploid sperm cells
Oogenesis produces one mature ovum or egg cell

7. CROSSING_OVER http://youtu.be/CCqAri4wtjQ BACK
Formation of homologous chromosomes called a tetrad
BACK

8. MEIOSIS
Form of cell division that produces daughter cells having half the number of chromosomes of the parent cell
Phases of meiosis similar to mitosis
Mitosis produces two genetically identical diploid cells from one diploid cell
Four phases
Cell divides once
Meiosis creates four genetically different haploid cells from one diploid cell
Eight phases
Cell divides twice

9. PHASES OF MEIOSIS Meiosis I 1. Prophase I 2. Metaphase I 3. Anaphase I
4. Telophase I and
Cytokinesis I
Meiosis II
5. Prophase II
6. Metaphase II
7. Anaphase II
8. Telophase II and
Cytokinesis II

10. MEIOSIS I Prophase I  crossing-over occurs (genetic variation) NEXT
Metaphase I  independent assortment VIEW
Anaphase I  homologous chromosomes separated
Telophase I & Cytokinesis I  two daughter cells formed
CONTINUE

11. INDEPENDENT ASSORTMENT
RETURN

12. MEIOSIS II Prophase II Metaphase II Anaphase II
Telophase II & Cytokinesis II
Note: DNA is not replicated
again between Meiosis I
and Meiosis II
Summary: At the end of meiosis, 4 daughter cells are formed = eggs or sperm. Each contains half as many chromosomes as the parent cell (n); each cell is genetically different from its parents and from its "siblings". Fertilization of an egg by a sperm restores the chromosome number to 2n.

13. GENETIC VARIABILITY OF FOUR HAPLOID CELLS

14. Lesson Summary—Meiosis
Asexual reproduction produces a clone, an organism that is genetically identical to its
parent.
Asexual reproduction includes binary fission, budding, and spore formation.
Sexual reproduction involves haploid gametes and produces a diploid zygote through
fertilization.
Meiosis is a type of cell division that halves the number of chromosomes. There are
eight stages of meiosis, divided into meiosis I and meiosis II. DNA is not replicated
between meiosis I and meiosis II.
Crossing-over, the independent assortment of chromosomes during anaphase I, and
random fertilization result in genetic variation.
Meiosis is a step during spermatogenesis and oogenesis. Spermatogenesis produces
four haploid sperm cells, while oogenesis produces one mature ovum.
Eukaryotes have three different versions of the sexual life cycle: a haploid life cycle, a
diploid life cycle, and a life cycle known as the alternation of generations. The sexual
life cycle depends on when meiosis occurs and the type of cell that undergoes meiosis.