Bellringer- Monday 4/22/13 1.What is MITOSIS? (give simple explanation) 2.At the end of Mitosis You have cells that are 3.Referring to #2, are there any cells that you have that might not go through Mitosis but might go through a DIFFERENT PROCESS? THINK!!!!! CANCER BROCHURE AND HW DUE FRIDAY!!

Bellringer- Thursday 4/25/13 1.How many chromosomes are in human body cells? 2.Your chromosomes occur in that means you get one from _____ and one from

DON’T FORGET…… CANCER BROCHURE AND HW DUE TOMORROW!!

Bellringer- Friday 4/26/13 TURN IN HOMEWORK AND CANCER BROCHURE What are homologous chromosomes? Who do homologous chromosomes come from? How are homologous chromosomes related?

Chromosomes occur in PAIRS!! Where do the chromosomes in each pair come from?

Genes- sections of a chromosome responsible for one trait (eye color, height, etc)

Paired chromosomes with genes for the same traits and their copies (from mom and dad) What are homologous chromosomes?

MEIOSIS

What is MEIOSIS? Division of a diploid cell that results in 4 haploid sex cells!

Why do we need meiosis? To reduce the number of chromosomes in 1/2 in our sperm and egg! Why 1/2 the chromosomes in sex cells? So the offspring has 1 complete set of chromosomes (50% from mom and 50% from dad)!

Meiosis – PMAT I and II Parent cell 4 daughter cells Meiosis I:Reduction Meiosis II: Division

Meiosis Parent cell – chromosome pair (46) Chromosomes replicated in Interphase (46 X 2) Meiosis I – Reduction in number of chromosomes (46) Meiosis II – Division of cells into 4 daughter cells with ½ the no. of chromosomes (23)

Meiosis I Prophase I: *homologous pairs pair up *Crossing over occurs! Metaphase I: *homologous chromosomes align in the middle

Anaphase I: *homologous chromosomes separated Telophase I: *2 daughter cells

Meiosis II Prophase II: *chromosomes start to move toward the center Metaphase II *chromosomes line up in the center

Anaphase II: *chromatids separate Telophase II: *4 daughter cells with half the amount of chromsomes of the parent cell

AGAIN…AFTER MEIOSIS… 4 Sex cells that are haploid (n) - half as many chromosomes as parent cell (2n)

Crossing-Over in PROPHASE I Chromosomes exchange genetic material between homologous pairs!

Because of Crossing over…… 1.More than 8 million different kinds of eggs and sperm can be produced trillion different zygotes possible

Chromosomes = condensed chromatin (DNA) Made up of TWO Sister Chromatids

A cell with TWO of each kind of chromosome (One from each parent) A cell with ONE of each kind of chromosome n = number of chromosomes from each parent

GAMETES= SEX CELLS

Haploid Diploid OrganismSex Cell (n)Body Cell (2n) Humans2346 Mosquito36 Toad1122 Potato2448 Dog3978 TRUE OR FALSE The # of chromosomes a species has is NOT related to how complex that organism is

New cells have the SAME number and kind of chromosomes as the ORIGINAL (parent) cell MITOSIS

IF GAMETES WENT THROUGH MITOSIS… Fertilization What is wrong with this??????

What next? Fertilization Egg (n) + Sperm (n) = Zygote (2n) 23 chromosomes 46 chromosomes

Fertilized egg with diploid set of chromosomes is called a zygote. After fertilization, the zygote divides by mitosis and becomes an embryo. Later, the embryo becomes a fetus Zygote>Embryo>Fetus

What happens during Meiosis?

Mitosis vs. Meiosis

Boy or Girl? The Y Chromosome “Decides”