AP Bio: Thursday 3/15/12 Sexual Reproduction & Meiosis

AP Bio: Thursday 3/15/12Sexual 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: • A section of DNA that holds instructions for

making one proteinEx: gene for hemoglobin protein

Homologous Chromosomes:• A pair of chromosomes that contain the same genes but not

necessarily the same alleles

Chromosome: • A long strand of DNA, coiled and

wrapped up, that contains many genes

Alleles:• Different versions of a gene Ex: normal hemoglobin allele vs.

mutated hemoglobin allele

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 3/16/12Details 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

End: End:

Start: Start:

Mitosis:

Meiosis II:

Meiosis I:

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

Start: Diploid Cell

(46 Chromosomes in Humans)

Start: Diploid Cell

(46 Chromosomes in Humans)

Mitosis: chromosomes line up single file and sister chromatids split

Meiosis II: sister chromatids split (like mitosis)

Meiosis I: chromosomes line up with homologous pairs, which then separate (sister chromatids stay together)

Summary of Meiosis

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

Summary of Meiosis

Stages of Meiosis

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?

Two Ways meiosis generates genetic diversity between gametes:

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 3/20/12Variations 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