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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: - PowerPoint PPT Presentation
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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