Which animal will stay warm longer, a mouse or an elephant?

Define in your own words (p. 275) Meiosis Diploid Haploid Gamete Crossing Over Chromosomes

Draw a chromosome. Explain what a chromosome is. Daily Question Draw a chromosome. Explain what a chromosome is. Why is crossing over important?

Eukaryotic Chromosomes All eukaryotic cells store genetic information in chromosomes Human body cells have 46 chromosomes or 23 identical pairs

Chromosomes in Dividing Cells Two sides of a chromosome are called chromatids & are held together by the centromere Called Sister Chromatids

Chromosome Structure Chromosomes contain DNA and Protein packed together to form chromatin. Chromatin is made of DNA that is wrapped around the protein, histones. Histone and DNA forms clusters called nucleosomes.

The Y Chromosome Decides Boy or Girl? The Y Chromosome Decides Y - Chromosome X - Chromosome

Daily Question Explain the differences between homologous chromosomes and sister chromatids.

Cell Reproduction

Meiosis Formation of Gametes (Eggs & Sperm)

Facts About Meiosis Two meiotic divisions --- Meiosis I and Meiosis II Original cell is diploid (2n) Four daughter cells produced that are haploid (1n)

Meiosis: Two Part Cell Division Sister chromatids separate Meiosis I Meiosis II Homologs separate Diploid Diploid Haploid

Meiosis I: Reduction Division Nucleus Spindle fibers Nuclear envelope Early Prophase I (Chromosome number doubled) Late Prophase I Metaphase I Anaphase I Telophase I (diploid)

DNA replication occurs Nucleus Spindle fibers Nuclear envelope Interphase Before Meiosis Begins DNA replication occurs

Prophase I Crossing over occurs- homologous chromosome- Form Tetrad

Tetrads Form in Prophase I Homologous chromosomes (each with sister chromatids)   Join to form a TETRAD

Crossing-Over Pieces of genes are exchanged

Homologous Chromosomes During Crossing-Over

1. Crossing-over occurs during: A. anaphase 1 B. Metaphase 1 C 1. Crossing-over occurs during: A. anaphase 1 B. Metaphase 1 C. Prophase 1 D. Prophase 2 2. Which of the following cells undergo meiosis? A. Sperm Cells B Liver Cells C. Unicellular organisms D. All of the above

Explain all parts of a chromosome, in words and drawings. Quiz Explain all parts of a chromosome, in words and drawings. Define diploid, chromatin, sister chromatids, and centromere. Extra Credit: What phase is technically not part of meiosis? Why?

Homologous pairs of chromosomes align along the equator of the cell Metaphase I Homologous pairs of chromosomes align along the equator of the cell

Anaphase I Homologs separate and move to opposite poles. Sister chromatids remain attached at their centromeres.

What is the difference between Metaphase and Anaphase? Break What is the difference between Metaphase and Anaphase? What is the job of the centrioles?

Telophase I Nucleus reassembles. Spindle fibers disappear Cytokinesis divides cell into two.

What is the difference between Interphase and Prophase? Break What is the difference between Interphase and Prophase?

Explain what occurs in Meiosis I, in your own words. Daily Question Explain what occurs in Meiosis I, in your own words.

Meiosis II Meiosis II produces gametes with Only one homolog of each chromosome is present in the cell. Gene X Meiosis II produces gametes with one copy of each chromosome and thus one copy of each gene. Sister chromatids carry identical genetic information.

Meiosis II: Reducing Chromosome Number Prophase II Metaphase II Telophase II Anaphase II 4 Identical haploid cells

Prophase II Nuclear envelope disappears. Spindle forms. Half the number of chromosomes as original in each cell

What is the difference between Prophase I and Prophase II? Break What is the difference between Prophase I and Prophase II? What is the difference between the cells at the end oogenesis and spermatogenesis?

At the very end of meiosis II each cell has 23 chromosomes. Daily Question At the very end of meiosis II each cell has 23 chromosomes. How many chromosomes are created during Interphase? How many chromosomes does the cell have at the very start of Prophase I?

Metaphase II Chromosomes align along equator of cell.

Anaphase II Sister chromatids separate and move to opposite poles. Equator Pole Sister chromatids separate and move to opposite poles.

What is the difference between Anaphase I and Anaphase II? Break What is the difference between Anaphase I and Anaphase II?

Telophase II Nuclear envelope assembles.

Cytokinesis II Gametes (egg & sperm) form Four haploid cells with one copy of each chromosome Different combinations of different genes Hybrid offspring

Meiosis results in _____ A. 2 haploid daughter cells B. 4 haploid daughter cells C. 2 diploid daughter cells D. 4 diploid daughter cells

The picture depicts what stage of meiosis?         A. Prophase 1 B. Anaphase 1 C. Metaphase 1 D. Metaphase 2

Name of Process in Gametes Egg: Oogenesis Formation of 1 true egg and 3 polar bodies Sperm: Spermatogenesis Formation of 4 true sperm cells

Winter Break Extra Credit Make an information pamphlet about one specific genetic diseases. The following must be included: What is the disease? What does the disease do to the body it is affecting? When was the disease discovered? Who discovered it? What type of mutation causes the disease? What are the tests to see if a person has the disease? How many people get this disease? Any other important information people need to know about the disease. Pictures

Holiday Science If you don’t bring something you can’t eat anything! Friday December 19, 2008 Bring some food to share with the class. It can be anything you enjoy! If you don’t bring something you can’t eat anything!