AP Bio: Wednesday, 3.9.11Sexual Reproduction & Meiosis

Homework due tomorrow: PS 14 and completed Embryonic Development packet (stapled

together) Also – short quiz tomorrow – study the problem set!

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)

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…

AP Bio: Thursday, 3.10.11Quiz: Mitosis & Embryology

Homework for Monday: PS 15 #1, 2 and one other question (bring notes for

the other question) Complete Lab 3B

Do Now: Hand in PS 14 plus the Embryology worksheet Get work back (Test 8 and PS 13) Get a PS 15 and sign up for one question other than

#1-2 Today’s Goals / Agenda:

Quiz your knowledge of mitosis and embryology Complete Lab 3B

AP Bio: Tuesday, 3.15.11Details of Meiosis

Homework: Completed Transformation Lab Report due tomorrow PS 15 due Thursday

Do Now: (please write down your answers) What is the overall goal of meiosis? What are 3 key differences between mitosis and meiosis?

Today’s Goals: Explain how meiosis creates genetic diversity between

gametes Agenda:

Special Thursday? AP Exam Sign-Up Lecture/Discussion Work time on assigned PS 15 questions Presentation on PS 15 #4

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)

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

Meiosis generates genetic diversity between gametes: Two Ways

1. 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?

2. 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.

Meiosis generates genetic diversity between gametes: Two Ways

AP Bio: Wednesday, 3.16.11Details of Meiosis

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