Bio 201 F07 True lect 4 post

Bio 201 F07 True lect 4 post - A question Which of the...

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Which of the following satisfies the modern definition of evolution we discussed. A. Variation within a species B. A change in the frequency of a heritable trait over time in a population C. Extinction of a species D. An environmental change causing reduced survival E. None of the above A question
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Populations should “homogenize” - but they don’t! Inside Darwin’s world
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Outside Darwin’s world: Mendel: Particulate inheritance
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Linnaeus (Taxonomy) Cuvier (Paleontology) Darwin (evol, natl sel ) Lamarck (evol, mech.) 1700 1725 1750 1775 1800 1825 1850 1875 1900 Lyell ( uniformitarianism ) Mechanism of inheritance Mendel (Genetics) Chromosomal theory of inheritance
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Chromosomes • First discovered in plants and worms in 1842, using microscopy on tissue preparations stained with various dyes • Later named “chromosomes” (color bodies) Drosophila larval salivary gland chromosomes Human mitotic chromosomes
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Chromosomes • Linear molecule of DNA – Normally not visible (interphase cells) • Visible in: – Mitosis (various cell types) and meiosis • Highly condensed and packaged with proteins – In some tissues when chromosomes are massively over-replicated (many thousands of copies aligned side-by-side) • Why would cells do this? Drosophila larval salivary gland chromosomes Human mitotic chromosomes
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Chromosome theory of inheritance • Theory: chromosomes are linear arrangements of genes - combined cell biology and genetic data • Established in the early 20th century from many observations in several organisms – Peas • William Bateson; 1st to the term “genetics” • Hugo DeVries Drosophila • Thomas Hunt Morgan – Salamander ( Batrachoseps attenuatus) • F.A. Janssens Drosophila larval salivary gland chromosomes Human mitotic chromosomes California slender salamander Batrachoseps attenuatus
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Mitosis • Mitosis: DNA replication/cell division during growth and development (in multicellular plants and animals) • Takes place in all somatic tissues • One diploid (2N) cell replicates its chromosomes (“4N”) and then divides once, resulting in two diploid (2N) daughter cells that are exact copies of the original cell • [N refers to the haploid chromosome number. N for humans = 23, N for Drosophila melanogaster = 4]
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Bio 201 F07 True lect 4 post - A question Which of the...

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