Chapter 17 Multiple choice questions

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What's the point of random mutagenesis? Select all correct answers.

Random mutagenesis was the first way developed to produce mutations in a candidate gene, and became redundant after the discovery of methods to genetically engineer the genome correct incorrect

Random mutagenesis is a powerful method for finding genes that are critical for a trait correct incorrect

Random mutagenesis is a way of generating mutations in any gene in the genome and hence for finding genes that are involved in a trait correct incorrect

Random mutagenesis is used for confirming the relationships between genes acting on a phenotype and is thus essential for investigating epistatic interactions correct incorrect

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What was found when random mutagenesis was first applied to circadian behavior in fruit flies? Select all correct answers.

The mutagenesis experiments demonstrated that circadian behavior was highly polygenic, arising from the conjoint effect of many loci of small effect correct incorrect

Mutagenesis identified a small number of dominant acting mutations, all of which turned out to be lethal correct incorrect

Mutagenesis created three alleles of a single gene affecting circadian behavior correct incorrect

Mutagenesis and subsequent genetic mapping identified a locus on the fly's X chromosome that altered circadian behavior, and led to the identification of the period gene correct incorrect

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What makes the fruit fly's clock tick? Select correct answer.

The joint action of a large number of proteins, encoded at multiple loci across the genome, ensure that the fly's clock accurately keeps a 12 hour cycle correct incorrect

Analysis of genetic mutations identified a feedback loop between protein constituents that occurred over the same time interval, thus providing a clock mechanism correct incorrect

The fact that an arrhythmic mutant protein did not cycle revealed that a key mechanism underlying the fruit fly's clock was the period protein's ability to inhibit the transcription of its own mRNA correct incorrect

The period protein interacts with the cell's translational apparatus to inhibit its own production, thus resulting in the cycling of the protein levels that underlies the fruit fly's clock correct incorrect

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What explains the clock's ability to respond to light? Select all correct answers.

A protein called cryptochrome acts a light sensor, and binds to part of clocks' core machinery called timeless correct incorrect

After cryptochrome binds to timeless, timeless is degraded and the cycling mechanism is reset correct incorrect

Cryptochrome is hidden in the nucleus, only emerging in response to light and hence contributing to the cycle of protein production and degradation that characterizes the clock correct incorrect

Neuronal connections from the retina convey information about light to a key brain area controlling rhythmicity in the hypothalamus correct incorrect

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Do mammals use the same clock mechanism as flies? Select correct answer.

Mutagenesis experiments in mice identified a completely different set of proteins underlying circadian behaviors from those found in the fruit fly correct incorrect

The mouse and fly mechanisms are identical with all the key molecules playing the same roles correct incorrect

While the overall mechanism for circadian rhythms is the same in flies and mice, there some important differences correct incorrect

Insufficient molecular characterization of the two species makes it impossible to determine whether the mechanisms for circadian rhythms are similar or not correct incorrect

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Why did mutagenesis reveal the mechanism of circadian biology but fail to uncover similarly fundamental mechanisms underlying other behavioral phenotypes? Select all correct answers.

The way mutations disrupt circadian biology is different from the effects of mutations on fear, anxiety and other psychological traits correct incorrect

The evolutionary origins of behavioral traits determines their genetic architecture and this likely explains the differences seen for circadian biology correct incorrect

Attempts to identify mutations that disrupt psychological traits have not adequately deployed random mutagenesis correct incorrect

The effect sizes seen in mutagenesis experiments are easily lost among the background effects of naturally occurring variation and so can never successfully be used to identify the genes involved in behavior correct incorrect