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Announcements:

• Sorry, I am not yet finished grading your exams. I'm working on it, and I'll let you know via e-mail when they're done.
• Homework #5 (on the Lycan reading) will be due next Monday, and will be posted soon
• Homework #6 (on chapter 9) will be due the Monday after that, and will be posted next week

Learning objectives for Monday, 10/9/00:

Students should be able to…

1) Describe the paradox posed by a comparison of genome size to organismal complexity.

2) Describe an early experiment (Britten and Kohne) that demonstrated the existence of repetitive sequences in mammalian DNA. Explain the rationale behind the experimental approach and the interpretation of the results (this is not in your textbook--I'll explain it in class)

3) Give examples of several categories DNA repeats of intermediate size, including both functional and nonfunctional sequences. Explain the origin of each and, if applicable, the evolutionary advantage it confers.

4) Explain what is meant by the term "satellite" DNA, and where such DNA can be found in the human genome.

Outline:

• Genome size is not strictly proportional to an organism's complexity
• Higher eukaryotes have large amounts of repeated DNA--about half the genome in humans and other mammals (much more in some plants and amphibians)
• Repeats can be classified into intermediate (repeated sequence is relatively long and complex) and simple repeats
• Intermediate repeats include tandemly repeated genes, multigene families, pseudogenes, and mobile elements
• Simple repeats are satellite DNA
• Clustered at centromeres and telomeres
• Smaller repeated regions are also scattered throughout genome
• Basis of DNA fingerprinting techniques (VNTR regions are simple repeats)

Topics to come on Wednesday:

• Mobile genetic elements
• Organellar DNA
• (if time permits) Chromatin structure

Chapter 9 topics we'll skip:

• Details of retroviral replication (figure 9-16)
• Functional rearrangements in DNA (section 9.4), including antibody gene assembly
• Morphology and functional elements of chromosomes (section 9.6)

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