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Chapter 4. The Structure and Function of Genes

The "one-gene, one-enzyme" hypothesis as put forth by Beadle and Tatum

A. has stood the test of time and still remains a solid working model.

B. has been proven to be completely incorrect.

C. has now been shown to be an overly simple representation.

D. is true for plants, but not humans.

E. applies to most human diseases.

C is the correct answer. The other answers are incorrect because:

  • A. Like most early concepts in genetics, newer information has shown that the original suppositions need to be changed/updated.

  • B. The concept is not completely wrong. It does hold true for selected conditions such as inborn errors of metabolism.

  • D. The principles are the same in plants and animals.

  • E. Few human diseases are this simple.

Genes are expressed

A. almost exclusively through protein coding.

B. usually in isolation, not by interacting with other genes.

C. by a variety of different mechanisms—some of which do not entail protein coding.

D. only in the nucleus.

E. only due to information in the coding sequence.

C is the correct answer. The other answers are incorrect because:

  • A. The key theme of this chapter is that genetics is not just about protein coding.

  • B. Gene-gene interactions are common.

  • D. Gene expression can occur outside of the nucleus, for instance in the mitochondria.

  • E. Changes in non-coding sequences can affect gene expression.

Satellite DNA

A. is composed of tandem repeats of nucleotide sequences.

B. excludes the centromere.

C. are interesting genetic phenomena, but have little clinical significance.

D. are subclassified as macro- and megasatellites.

E. is typically very homogeneous.

A is the correct answer. The other answers are incorrect because:

  • B. The centromere is largely composed of alpha satellite material.

  • C. Changes in satellite DNA can produce many different genetic syndromes.

  • D. Some types of satellite DNA are classified as mini- and micro-satellites.

  • E. Satellite DNA is notoriously heterogeneous. This makes it particularly attractive for marker or linkage studies.

Fragile X syndrome

A. is ...

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