1. Mitosis Cell division/ cell production What kind of cells?
Nerve, skin, epithelial, etc.- somatic
Same / all the time
Mitosis is reproduction in which cells produce identical replicas
Organic growth of tissues, fibers, and membranes

2. MEIOSIS

3. Meiosis
Meiosis occurs in sexual reproduction when a diploid germ cell produces four haploid daughter cells that can mature to become gametes (sperm or egg).

4. Meiosis The genetic code of a human contains 46 chromosomes
Half of this number is in egg and sperm
Divided twice which turns out 4 cells (gametes)
Each of these will have only half of the number of chromosomes; but each will contain genetic info from each parent
On handout- diff phases – ones we won’t go over - I will tell you what you are resp. for

5. Mitosis Meiosis Number of divisions 1 2 Number of daughter cells 4
Genetically identical?
Yes No
Chromosome #
Same as parent
Half of parent
Where
Somatic cells
Sex cells
When
Throughout life
At sexual maturity
Role
Growth and repair
Sexual reproduction

6.
Another version explaining meiosis- show if overall class isn’t getting it or if there is time

7. Interphase I
Cells undergo a round of DNA replication forming duplicate chromosomes
Each chromosome has two sister chromatids held together by a centromere

8. Prophase I Chromosomes coil up and spindle forms
Each chromosome pairs with its corresponding homologous chromosome to form a tetrad
Crossing over may occur when chromatids exchange genetic material
Crossing over results in new combinations of alleles on a chromosome
Crossing over- process in which homologous chromosomes exchange portions of their chromatids.
Alleles-different forms of a gene

9. Crossing Over

10. Metaphase I
The centromere of each chromosome becomes attached to a spindle fiber
Spindle fibers pull the tetrads to the equator of the spindle
Homologous chromosomes are lined up side by side as tetrads
“met a “ in the middle

11. Anaphase I
The fibers pull the homologous chromosomes toward opposite end of the cell
Centromeres do not split
This ensures that each new cell will receive only one chromosome from each homologous pair
“ana “ new cell gettin’ ready to form

12. Telophase I The spindle breaks down and the chromosomes uncoil
The cytoplasm divides to yield two new cells
Each cell has half the genetic info of the original cell because it has only one homologous chromosome from each pair
Cleavage furrow

13. Prophase II
Meiosis I results in two haploid (N) daughter cells, with half the number of chromosomes as the original cell
A spindle forms in each of the two new cells and the fibers attach to the chromosomes
Haploid- a cell that only contains a single set of chromosomes and therefore a single set of genes

14. Metaphase II
The chromosomes line up in a similar way to the metaphase stage of mitosis
The chromosomes are pulled to the center of the cell and line up randomly at the equator
Met a again

15. Anaphase II The centromere of each chromosome splits
The sister chromatids separate and move toward opposite ends of the cells
BOOM Sister chromatids- after replication, two duplicated chromosomes are still joined to each other

16. Telophase II Nuclei re-form The spindles breakdown
The cytoplasm divides
Cells for gametes

17. Meiosis II Meiosis II results in four haploid (N) daughter cells.
Each haploid cell contains one chromosome from each homologous pair
Haploid cells will become gametes transmitting genes to off spring
This is where I got one gene from mom and 1 gene from dad

18. What Meiosis is About
Meiosis allows the creation of unique individuals
through sexual reproduction.