Aim for FiveBiology

Analyze data

Gene expression in different tissues

  • Unit 6
  • 4 points
  • About 10 minutes

You can use a calculator on this question, just like on exam day.

A short question with data in a table or graph. You describe what the data show, use the data to judge a hypothesis, and explain how the results connect to biology you know. On the exam: Question 6 of 6 in Section II; about 10 minutes suggested.

The question and its sources

Researchers studied three genes in mice. Gene L codes for a protein secreted by liver cells. Gene M codes for a protein found in muscle fibers. Gene G codes for an enzyme of glycolysis.

Investigation

The researchers collected liver, skeletal muscle and brain neuron tissue from five mice. They measured the relative amount of mRNA from each gene in each tissue (Table 1). They also tested genomic DNA from each tissue for the presence of each gene (Table 2).

Source: Hypothetical study

Table 1. Relative amount of mRNA, mean ± 2SE

GeneLiverSkeletal muscleNeurons
Gene L950 ± 602 ± 11 ± 1
Gene M3 ± 2820 ± 554 ± 2
Gene G410 ± 30395 ± 35402 ± 28

Source: Hypothetical data

Table 2. Presence of each gene in genomic DNA

GeneLiverSkeletal muscleNeurons
Gene LPresentPresentPresent
Gene MPresentPresentPresent
Gene GPresentPresentPresent

Source: Hypothetical data

Suggested time: 10 minutes

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Part (a)

1 point

Based on Table 1, identify the tissue in which Gene M is expressed at the highest level.

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Part (b)

1 point

Based on Table 1, describe the pattern of Gene G expression across the three tissues.

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Part (c)

1 point

A student claims that liver cells make much more Gene L mRNA than muscle cells do because muscle cells do not contain Gene L. Use the data to evaluate the student's claim.

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Part (d)

1 point

Explain how differences in transcription factors could lead to the pattern of Gene L expression shown in Table 1.

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