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Ch. 16 - How Genes Work
Freeman - Biological Science 7th Edition
Freeman7th EditionBiological ScienceISBN: 9783584863285Not the one you use?Change textbook
All textbooksFreeman 7th EditionCh. 16 - How Genes WorkProblem 12
Chapter 16, Problem 12

Investigators examined the expression of transporter mRNA and protein produced in zebrafish homozygous for each of the alleles and obtained the results summarized here (+=present,−=absent). Does the allele associated with light color appear to be altering transcription ortranslation? Why?
Table showing mRNA and protein expression for dark and light zebrafish alleles.

Verified step by step guidance
1
Examine the table to identify the presence or absence of mRNA and protein for both dark-colored and light-colored zebrafish alleles.
Note that the dark-colored zebrafish allele shows both mRNA and protein present (+).
Observe that the light-colored zebrafish allele shows both mRNA and protein absent (−).
Conclude that the absence of mRNA in the light-colored zebrafish allele indicates that transcription is being altered.
Since no mRNA is produced, translation cannot occur, leading to the absence of protein.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Transcription

Transcription is the process by which the genetic information in DNA is copied into messenger RNA (mRNA). This occurs in the nucleus of eukaryotic cells and is the first step in gene expression. The presence or absence of mRNA indicates whether a gene is being actively transcribed, which is crucial for understanding how alleles influence traits.
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1) Initiation of Transcription

Translation

Translation is the process by which ribosomes synthesize proteins using the mRNA transcript as a template. This occurs in the cytoplasm and involves the decoding of mRNA into a specific sequence of amino acids, forming a protein. The presence of protein indicates successful translation, which is essential for determining the functional outcome of gene expression.

Allelic Variation

Allelic variation refers to the differences in the DNA sequence of genes among individuals, which can lead to different traits. In this context, the light-colored zebrafish allele shows a lack of both mRNA and protein expression, suggesting that this allele may disrupt either transcription or translation, affecting the phenotype of the organism.
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Sources of Genetic Variation
Related Practice
Textbook Question

Skin color is often one of the first traits people notice in each other. Studies in zebrafish uncovered a mutation that altered a transport protein and resulted in light-colored fish. This discovery led to the finding that the same gene in humans has a strong influence on skin pigmentation in many populations. The zebrafish mutation that reduced coloration created a null allele of the transport protein gene. Which of the following types of mutation would be most likely to create this null allele?

a. A missense mutation

b. A frameshift mutation

c. A neutral mutation

d. A silent mutation

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Textbook Question
Skin color is often one of the first traits people notice in each other. Studies in zebrafish uncovered a mutation that altered a transport protein and resulted in light-colored fish. This discovery led to the finding that the same gene in humans has a strong influence on skin pigmentation in many populations. The zebrafish mutation that reduced coloration created a null allele of the transport protein gene. Which of the following types of mutation would be most likely to create this null allele?a. a missense mutationb. a frameshift mutationc. a neutral mutationd. a silent mutation
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Textbook Question
Eating even a single death cap mushroom (Amanita phalloides) can be fatal due to a compound called αα-amanitin, a toxin that inhibits transcription.What would you predict to be the immediate outcome of adding αα-amanitin to a cell?a. reduced DNA synthesisb. reduced production of one or more types of RNAc. reduced binding of tRNAs to anticodonsd. reduced rate of translocation of ribosomes translating mRNA
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Textbook Question

A small portion of the human transport protein amino acid sequence is shown here. The upper sequence is associated with darker skin, and the lower sequence is associated with lighter skin. What DNA base-pair change created the light-skin form of the human protein from the gene that coded for the dark-skin form?

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Textbook Question

Researchers compared the amino acid sequences of the transport protein in zebrafish, puffer fish, mice, and humans. They found many stretches with identical sequences in all four species. Does this mean that the corresponding mRNA base sequences are also the same in these four species? Explain why or why not.

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Textbook Question

The allele of the human transport protein associated with lighter skin is found almost exclusively in people with European ancestry. The other common allele for darker skin, which appears to be the ancestral allele, is found in people with African ancestry. What is a plausible explanation for how the lighter-skin allele came to be so common in those with European ancestry?

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