Meiosis-A prelude to reproduction
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Transcript of Meiosis-A prelude to reproduction
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Meiosis-A prelude to reproduction
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I. Terminology
• A. karyotype– 1. human 46
chromosomes
– 2. homologous pairs
– 3. diploid condition
– 4. note various sizes and shapes
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B. Chromatin
• 1. 1.8 meters• 2. DNA• 3. exists in a non-dividing cell
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C. Relationship between chromatin and chromosome
• 1. chromatin• 2. chromosomes• 3. histone proteins• 4. nucleosome
100µm
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D. Terms of chromosome structure
• 1. Monad• 2. Dyad• 3. Centromere• 4. Sister chromatids
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E. Homologous chromosome pairs
• 1. definition• 2. paternal vs.
maternal• 3. genes vs. alleles• 4. synapsis• 5. tetrad• 6. sister vs. nonsister
chromatids
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How many chromosomes do you see?
83%
17%
0%0%
Enter answer text...
1. 42. 83. 104. No clue
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II. Review of mitosis
• A. Prophase• B. Metaphase• C. Anaphase• D. Telophase• E. Products
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III. Meiosis overview
• A. Importance?• B. Two separate
divisions– Meiosis I reduction
division– Meiosis II “mitotic-like”
division
• C. Where does it occur?
D. What does meiosis produce?
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IV. Meiosis I
• A. Prophase I• B. Metaphase I• C. Anaphase I• D. Telophase I• E. End products
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V. Meiosis II
• A. Prophase II• B. Metaphase II• C. Anaphase II• D. Telophase II• E. Final products
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VI. Comparison between mitosis and meiosis
Event Mitosis Meiosis I Meiosis II
Synapsis occurs
Sister chromatids separate
Homologous chromosomes separate
Crossing over occurs
Tetrads form
Haploid cells form
Identical daughter cells form
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VII. Meiosis and simple inheritance
• A. Sex determination • 1. autosomes• 2. sex chromosomes• 3. products of meiosis• 4. nature of sperm
determines sex• 5. sex ratios
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B. Inheritance of somatic traits
• 1. Theory of particulate inheritance• 2. Each body trait is affected by two alleles• 3. One inherited from father and other from mother• 4. Two factors separate upon gamete formation during
meiosis• 5. Terms of inheritance
a. dominant
b. recessive
c. genotype
d. phenotype
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6. Inheritance of eye color
• a. Dominant allele produces pigment (E)• b. Recessive allele produces no pigment (e)• c. Possible genotypes• d. Resulting phenotypes
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7. Sample problem
• In humans, freckles are dominant to no freckles. Mary, who has no freckles, is planning on having children with Paul. Paul, who has freckles, was born to a freckless woman. Mary wants to know the probability of her in utero son has of having freckles.
• How do we start?• List the symbols to be used to represent the alleles.• What is the mother’s phenotype? Genotype?• What is the father’s phenotype? What does his
genotype have to be?• What alleles are carried in the eggs and sperm of the
couple?• Create the punnett square.• What will be the name of the son which is not born yet?