Bellwork: Identify which “PHASE” the cells are going through and DRAW that cell.

Prepare your Journals for Cornell Notes Page 47 Title: Meiosis Essential Question: What is meiosis and how is it different than mitosis?

Quiz Tomorrow

Standard: (B.6G) recognize the significance of meiosis in sexual reproduction

1. What are Chromosomes?

Chromosomes: coiled DNA located in the cell nucleus. An organism inherits one of each chromosome from each parent. Homologous chromosomes = 2 copies of each chromosome

Before After A karyotype is a picture of a person's chromosomes. In order to get this picture, the chromosomes are isolated, stained, and examined under the microscope. A picture is taken. Then, the picture is cut up and rearranged by the chromosome’s size. The chromosomes are lined up from largest to smallest. A trained cytogeneticist can look for missing or extra pieces of chromosome.

Diploid: A cell that contains 2 sets of homologous chromosomes n = the number of chromosomes *two sets of “red, blue, yellow”

Most Mammals are Diploid Organisms…Including you!! Humans: 46 (23 sets) Gorilla: 48 (24 sets)Elephant: 56 (28 sets) Coyote: 78 (39 sets) Goat: 60 (30 sets)

Which “birdie” do you agree with more?

2. Sexual Reproduction & Our Cells

On a cellular level, what happens during sex? Biologically speaking, what’s the point of sex?

Sexual reproduction= DNA combined from 2 parents Gametes = sex cells Male Gamete= sperm Female Gamete = egg

If YOU are human, then YOUR cells have 46 chromosomes and your parents’ cells each have 46 chromosomes. Agreed? If you get DNA from both your parents then why wouldn’t you end up with 92 chromosomes? Aaron: It’s because the male gamete actually only contributes 35 of the chromosomes and the female gamete contributes the remaining 11 Brittney: When the male and female gamete join, the result is 92 chromosomes but as the baby develops, chromosomes that are not needed are destroyed during mitosis. Karen: There must be some way that the male and female gamete each carry only 23 of the chromosomes from each parent so that when they get together they equal 46. Blake: The gametes each contain the full 46 chromosomes from each parent but when fertilization occurs only the first 23 that pair up are used.

When gametes (sex cells) are formed, a process occurs that separates the two sets of genes so that each gamete ends up with just one set. Karen: There must be some way that the male and female gamete each carry only 23 of the chromosomes from each parent so that when they get together they equal 46.

Haploid = cells that contain only 1 set of chromosomes Gametes = haploid N= number of sets of chromosomes in the cell

3. Meiosis

The Meiosis process involves TWO cell divisions that result in FOUR haploid gametes. ** Meiosis is how gametes are produced** 1. 2.

Mom’s chromosome Dad’s chromosome Identical Copy MITOSIS

During Meiosis, a period of crossing over occurs genetic material is exchanged between the maternal and paternal sets of chromosomes present in the cell. Crossing over results in genetic variation. Dad’s chromosome Mom’s chromosome Crossing Over DNA Replication Crossing Over

The diagram below shows the possible variations for just one chromosome set going through Meiosis. Imagine the possibilities you could get with 46!!!

Mitosis vs. Meiosis

Set this table up in your journal. MitosisMeiosis

Mitosis results in two genetically identical diploid cells. Meiosis results in four genetically different haploid cells.

Mitosis is used for growth and repair. Meiosis is used for gamete production and increased genetic variation.

Finish Your Work from yesterday Mitosis Identification: Make sure you have the reason you put your answer next to the phase you chose. Comic Strip: All phases of mitosis At least 6 “scenes” (You can draw the steps) Make sure you say what’s going on in each picture Colored Use these words: Interphase, Prophase, Metaphase, Anaphase, Telophase, Cytokinesis