AP Bio: Thursday 3/15/12 Sexual Reproduction & Meiosis Homework due tomorrow: Lab 3B (Meiosis) Analysis Questions Do Now: On the handout… Today’s Goals: Explain the key steps of sexual reproduction Review key vocabulary terms Explain and model the steps and purpose of meiosis Agenda: Lecture/Discussion Lab 3B: Modeling Meiosis w/ Pipecleaners

Asexual vs. Sexual Reproduction Asexual Reproduction One parent Parent and offspring are genetically identical (clones) Reproduce using MITOSIS (euks) or BINARY FISSION (proks) or by BUDDING or FRAGMENTATION Sexual Reproduction Two parents Offspring are genetically different from parents Reproduce using MEIOSIS (makes eggs and sperm) and FERTILIZATION (egg and sperm join)

Sexual Reproduction Life Cycle

Major Genetics Terms Gene: Alleles: Chromosome: A section of DNA that holds instructions for making one protein Ex: gene for hemoglobin protein Alleles: Different versions of a gene Ex: normal hemoglobin allele vs. mutated hemoglobin allele Chromosome: A long strand of DNA, coiled and wrapped up, that contains many genes Homologous Chromosomes:  A pair of chromosomes that contain the same genes but not necessarily the same alleles

Major Genetics Terms (continued) Diploid: A cell that contains TWO COPIES of every chromosome (in homologous pairs) All human body cells except gametes are diploid. Haploid: A cell that contains ONE COPY of every chromosome Gametes are haploid.  Gametes: Egg or sperm cells, used in sexual reproduction. Contain HALF the number of chromosomes as all other body cells (they are haploid) Meiosis: The process of making gametes. 1 Diploid cell  4 Haploid cells Separates homologous chromosomes into different cells Unlike in mitotic cell division, the resulting daughter cells are NOT identical

Meiosis

Watch the video…

Lab 3B: Meiosis w/ Pipecleaners!

AP Bio: Friday 3/16/12 Details of Meiosis Homework: Take notes and be ready to present on your assigned problem set question PS 15 due Wednesday 3/21/12 Do Now: Get a copy of PS 15 and adjust the date (sorry!) Read questions 3-7 and pick one or more that you’re interested in Today’s Goals: Explain how meiosis creates genetic diversity between gametes Agenda: Lecture/Discussion: Details of Meiosis

Start: Start: Meiosis I: Mitosis: Meiosis II: End: End:

Start: Diploid Cell Start: Diploid Cell End: 4 Haploid Cells (46 Chromosomes in Humans) Start: Diploid Cell (46 Chromosomes in Humans) Meiosis I: chromosomes line up with homologous pairs, which then separate (sister chromatids stay together) Mitosis: chromosomes line up single file and sister chromatids split Meiosis II: sister chromatids split (like mitosis) End: 4 Haploid Cells (23 Chromosomes in Humans) Cells different from starting cell (half the # of chromosomes) End: 2 Diploid Cells (46 Chromosomes in Humans) Cells same as starting cell

Summary of Meiosis

Summary of Meiosis Final result: DNA is replicated once Chromosomes and cells are divided twice: Meiosis I: Homologous chromosomes pair up and separate Forms 2 haploid cells Chromosomes still have sister chromatids Meiosis II: Sister chromatids separate Final result: 4 haploid gametes with HALF the number of chromosomes as the original cell Gametes

Stages of Meiosis

Two Ways meiosis generates genetic diversity between gametes:

Two Ways meiosis generates genetic diversity between gametes: 1. Crossing over during Prophase I. One sister chromatid trades a section of DNA with its homologous partner. Creates new combinations of alleles on chromosomes. Can happen at multiple places along the chromosome, allowing for a nearly infinite number of different gametes.

Two Ways meiosis generates genetic diversity between gametes:

Two Ways meiosis generates genetic diversity between gametes: 2. Independent alignment of homologous pairs during Metaphase I. A cell with 2 homologous pairs yields 4 possible gametes. How many are possible with 23 homologous pairs?

Sexual Reproduction Generates Genetic Diversity in 3 Ways: Meiosis: Independent Alignment of Homol. Chromosomes in Metaphase I Meiosis: Crossing Over Fertilization: Random Selection of the Diverse Egg and Sperm Cells generated by Meiosis

Lab 3B Review…

AP Bio: Tuesday 3/20/12 Variations on Meiosis & Reproduction Homework: PS 15 due tomorrow. We WILL have class tomorrow @ 7:20 sharp. Do Now: Hand in Transformation Lab Report and get back other labs Group #3 – get ready to present Everyone else – what do you think are some differences between making eggs and making sperm? Today’s Goals: Apply knowledge of meiosis to… Various interesting and weird reproductive situations Explain Mendel’s Laws of Inheritance Agenda: PS 15 Presentations Chapter 14 – Reading & Worksheet