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3). Consider the four mutations (i-iv) described below: i. One of the mutations causing cystic fibrosis in humans is a deletion of three nucleotides that eliminates a phenylalanine at position 508 of the CFTR protein (D508). Normally, CFTR protein is localized to the plasma membrane, where it functions as a chloride ion channel. D508 CFTR is misfolded and all of it is degraded without ever reaching the cell surface. ii. The yeast transcription factor Gal4p contains a DNA-binding domain and a transcriptional activation domain. An allele with a deletion the gene portion encoding the activation domain encodes a truncated Gal4p containing only the DNA-binding domain. It binds to Gal4p target genes at appropriate binding sites in their upstream regulatory regions, but does not activate their transcription. In cells with both wild type and mutant forms of Gal4p, the truncated Gal4p binds more efficiently to target DNA sequences than wild type. iii. Mutations in the acid maltase gene in humans cause a metabolic disorder where glycogen over- accumulates in multiple tissues. In individuals with a relatively mild form of the disease, a single base pair change at an intron-exon boundary interferes with splicing most, but not all of the time; nozygous mutant cells have about 10% of normal enzyme activity. iv. Rhodopsin is a protein made in photoreceptor cells of the retina, which detect light to generate visual cues. A missense mutation in the rhodopsin gene produces a rhodopsin protein that is activate all the time, whether or not the eye is exposed to light, resulting in constant light perception. a. Which of these mutations is mostly likely to be a dominant negative mutation and why? b. Which of these is most likely to be a null loss of function mutation and why? c. Which of these is most likely to be a leaky loss of function mutation and why? d. Which of these is mostly likely to be a gain of function mutation and why?

3). Consider the four mutations (i-iv) described below: i. One of the mutations causing cystic fibrosis in humans is a deletion of three nucleotides that eliminates a phenylalanine at position 508 of the CFTR protein (D508). Normally, CFTR protein is localized to the plasma membrane, where it functions as a chloride ion channel. D508 CFTR is misfolded and all of it is degraded without ever reaching the cell surface. ii. The yeast transcription factor Gal4p contains a DNA-binding domain and a transcriptional activation domain. An allele with a deletion the gene portion encoding the activation domain encodes a truncated Gal4p containing only the DNA-binding domain. It binds to Gal4p target genes at appropriate binding sites in their upstream regulatory regions, but does not activate their transcription. In cells with both wild type and mutant forms of Gal4p, the truncated Gal4p binds more efficiently to target DNA sequences than wild type. iii. Mutations in the acid maltase gene in humans cause a metabolic disorder where glycogen over- accumulates in multiple tissues. In individuals with a relatively mild form of the disease, a single base pair change at an intron-exon boundary interferes with splicing most, but not all of the time; nozygous mutant cells have about 10% of normal enzyme activity. iv. Rhodopsin is a protein made in photoreceptor cells of the retina, which detect light to generate visual cues. A missense mutation in the rhodopsin gene produces a rhodopsin protein that is activate all the time, whether or not the eye is exposed to light, resulting in constant light perception. a. Which of these mutations is mostly likely to be a dominant negative mutation and why? b. Which of these is most likely to be a null loss of function mutation and why? c. Which of these is most likely to be a leaky loss of function mutation and why? d. Which of these is mostly likely to be a gain of function mutation and why?

Human Anatomy & Physiology (11th Edition)
Human Anatomy & Physiology (11th Edition)
11th Edition
ISBN:9780134580999
Author:Elaine N. Marieb, Katja N. Hoehn
Publisher:Elaine N. Marieb, Katja N. Hoehn
Chapter1: The Human Body: An Orientation
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Problem 1RQ: The correct sequence of levels forming the structural hierarchy is A. (a) organ, organ system,...
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3). Consider the four mutations (i-iv) described below: i. One of the mutations causing cystic fibrosis in humans is a deletion of three nucleotides that eliminates a phenylalanine at position 508 of the CFTR protein (D508). Normally, CFTR protein is localized to the plasma membrane, where it functions as a chloride ion channel. D508 CFTR is misfolded and all of it is degraded without ever reaching the cell surface. ii. The yeast transcription factor Gal4p contains a DNA-binding domain and a transcriptional activation domain. An allele with a deletion the gene portion encoding the activation domain encodes a truncated Gal4p containing only the DNA-binding domain. It binds to Gal4p target genes at appropriate binding sites in their upstream regulatory regions, but does not activate their transcription. In cells with both wild type and mutant forms of Gal4p, the truncated Gal4p binds more efficiently to target DNA sequences than wild type. iii. Mutations in the acid maltase gene in humans cause a metabolic disorder where glycogen over- accumulates in multiple tissues. In individuals with a relatively mild form of the disease, a single base pair change at an intron-exon boundary interferes with splicing most, but not all of the time; homozygous mutant cells have about 10% of normal enzyme activity. iv. Rhodopsin is a protein made in photoreceptor cells of the retina, which detect light to generate visual cues. A missense mutation in the rhodopsin gene produces a rhodopsin protein that is activate all the time, whether or not the eye is exposed to light, resulting in constant light perception. a. Which of these mutations is mostly likely to be a dominant negative mutation and why? b. Which of these is most likely to be a null loss of function mutation and why? c. Which of these is most likely to be a leaky loss of function mutation and why? d. Which of these is mostly likely to be a gain of function mutation and why?
Transcribed Image Text:3). Consider the four mutations (i-iv) described below: i. One of the mutations causing cystic fibrosis in humans is a deletion of three nucleotides that eliminates a phenylalanine at position 508 of the CFTR protein (D508). Normally, CFTR protein is localized to the plasma membrane, where it functions as a chloride ion channel. D508 CFTR is misfolded and all of it is degraded without ever reaching the cell surface. ii. The yeast transcription factor Gal4p contains a DNA-binding domain and a transcriptional activation domain. An allele with a deletion the gene portion encoding the activation domain encodes a truncated Gal4p containing only the DNA-binding domain. It binds to Gal4p target genes at appropriate binding sites in their upstream regulatory regions, but does not activate their transcription. In cells with both wild type and mutant forms of Gal4p, the truncated Gal4p binds more efficiently to target DNA sequences than wild type. iii. Mutations in the acid maltase gene in humans cause a metabolic disorder where glycogen over- accumulates in multiple tissues. In individuals with a relatively mild form of the disease, a single base pair change at an intron-exon boundary interferes with splicing most, but not all of the time; homozygous mutant cells have about 10% of normal enzyme activity. iv. Rhodopsin is a protein made in photoreceptor cells of the retina, which detect light to generate visual cues. A missense mutation in the rhodopsin gene produces a rhodopsin protein that is activate all the time, whether or not the eye is exposed to light, resulting in constant light perception. a. Which of these mutations is mostly likely to be a dominant negative mutation and why? b. Which of these is most likely to be a null loss of function mutation and why? c. Which of these is most likely to be a leaky loss of function mutation and why? d. Which of these is mostly likely to be a gain of function mutation and why?
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