Homework_9_01-30-09_C&A

Homework_9_01-30-09_C&A - Biology 5A Homework 9...

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Biology 5A Homework 9 January 30-February 2, 2009 1. Which of the following types of cytoskeletal fibers is NOT correctly matched with a type of motor protein? A. microtubules - kinesin B. intermediate filaments - keratin C. microtubules - dynein D. microfilaments - myosin E. all are correctly matched (Ans. B) 2. Chlamydomonas is a type of unicellular green algae that has two flagella that enable it to swim in the water in which it lives. Exposure to certain chemicals can cause mutations in Chlamydomonas . A mutation is a change in the sequence of bases in a DNA molecule, or gene. When a protein is made from a mutated gene, the protein is often defective because it has an improper amino acid sequence or, in other words, an improper primary structure. An experimenter applies a mutagenic chemical to Chlamydomonas and subsequently isolates a mutant that lacks the ability to swim. The experimenter examines the mutant Chlamydomonas by microscopy and finds that it has normal appearing flagella, but these flagella are unable to actively bend back and forth. Which of the following genes would be the most likely to have been mutated in this Chlamydomonas ? A. a gene that encodes actin B. a gene that encodes myosin C. a gene that encodes dynein D. a gene that encodes kinesin E. a gene that encodes intermediate filament protein (Ans. C) 3. According to the endosymbiont hypothesis, mitochondria and plastids originated as bacteria that were engulfed by primitive eukaryotic cells long ago in evolution and which survived in a mutually-beneficial relationship with the surrounding eukaryotic cytoplasm. The DNA that is found today in mitochondria and plastids traces back to the DNA that was present in the engulfed bacteria. Mitochondria
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Homework_9_01-30-09_C&A - Biology 5A Homework 9...

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