Meiosis Day 3

Concept check on Sexual and Asexual Reproduction Yes, you may use your notes!

Today’s Objectives: -Explain how the process of meiosis creates 4 haploid gamete cells that are genetically different from all others. -Be able to diagram the positions of chromosomes at key stages in the process and how this contributes to halving the amount of genetic material in gametes. Key phases include: prophase 1, metaphase 1, anaphase 1 and contrast these to metaphase 2 and anaphase 2 -Compare and contrast the process of meiosis to mitosis- How are they similar? How are they different?

Recap from Yesterday: Biological Success Haploid Diploid Gametes Fertilization Zygote Meiosis Mitosis

Karyotype: Full set of chromosomes in nucleus of every cell in an organism. Humans have 46 chromosomes which means 23 pairs of chromosomes. How many chromosomes would be in a sex cell?

STILL ONE CHROMOSOME DNA has been replicated

Find Your Homologous Partner! Without talking, see if you can find your homologous partner! How did you find your partner? What did you notice about your partner?

What is a homolog? Homologous chromosomes (homologs) are the pairs of chromosomes you get from EACH of your parents. One homolog you get from your mother. One homolog you get from your father. Homologs contain the same types of genes (hair color, eye color, blood type) Each homolog contains SPECIFIC info from EACH parent (Blonde hair, Brown eyes, B- blood type)

Prophase I Chromosomes have been duplicated in interphase These duplicated chromosomes pair up with their homologous partner. Long process

Prophase I Crossing over: The exchange of genetic material between homologs

Metaphase I The homologous pairs move to the center of the cell (metaphase plate) Spindle fibers attach to ONE chromosome (sister chromatids).

Anaphase I Two chromosomes separate and start moving toward opposite poles. Sister chromatids remain joined *In mitosis they separate

Telophase I The chromosomes complete migration. Each pole has a HAPLOID set of chromosomes. Each pole still has a set of sister chromatids. Nuclear envelope-> spindle disappears -> cytokinesis

Meiosis I

What were some differences between meiosis I and mitosis? Prophase I is longer in meiosis Prophase I includes crossing over Metaphase I pairs of chromosomes line up along meiotic equator. Anaphase I sister chromatids move together to same pole.

Prophase II Interphase occurs, but NO replication occurs. Spindle fibers form and attach to centromeres.

Metaphase II Chromosomes align just as they would in mitosis.

Anaphase II Chromosomes divide: ▫Sister chromatid separate

Telophase II 4 haploid nuclei are formed Cytokinesis occurs when the cytoplasm divides

Meiosis II

What are the differences between mitosis and meiosis?

Artistic Time