Concept explainers
Data analysis Two different genes have mutant alleles that cause this spotting
To determine: The function of other gene product in spotting phenotype, if one gene encodes a signaling molecule.
Introduction: A mutation can be defined as a sudden change that occurs in the DNA sequence, during DNA replication. It can also be caused by exposure to specific chemicals or radiation. Mutation contributes to genetic variability.
Explanation of Solution
Neural crest cell under the surface of ectoderm differentiates into pigment cells of the skin. Survival and migration of these cellsare affected by a mutation in genes leads to white spotting in the skin. Two different genes have a mutant allele that causes the spotting phenotype in humans and mice. One gene act as a signaling molecule then the other is likely to be a receptor for the molecule.
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Chapter 52 Solutions
BIOLOGY
- The photos below show flowers from two Arabidopsis plants. One plant is wild-type unmutated; the other carries a mutation in one of its ABC floral identity genes. This mutation causes sepals and petals to form instead of stamens and carpels. Refer to Figure 10.7 to decide which gene A, B, or C has been inactivated by the mutation.arrow_forwardEnhanced Spatial Learning in Mice With an Autism Mutation Autism is a neurobiological disorder with symptoms that include impaired social interactions and stereotyped patterns of behavior. Around 10 percent of autistic people have an extraordinary skill or talent such as greatly enhanced memory. Mutations in neuroligin 3, an adhesion protein that connects brain cells to one another, have been associated with autism. One mutation changes amino acid 451 from arginine to cysteine. In 2007, Katsuhiko Tabuchi and his colleagues genetically modified mice to carry the same arginine-to-cysteine substitution in their neuroligin 3. Mice with the mutation had impaired social behavior. To test spatial learning ability, the mice were placed in a water maze: a deep pool of warm water in which a platform is submerged a few millimeters below the surface. The platform is not visible to swimming mice. Mice do not particularly enjoy swimming, so they locate a hidden platform as fast as they can. When tested again, they can remember its location by checking visual cues around the edge of the pool. How quickly they remember the platforms location is a measure of spatial learning ability (FIGURE 15.18). FIGURE 15.18 spatial learning ability in mica mutation in neuroligin 3 (R451C), compared with unmodified (wild-type) mica. 2. Did the modified or the unmodified mice learn the location of the platform faster in the first test?arrow_forwardEnhanced Spatial Learning Ability in Mice Engineered to Carry an Autism Mutation Autism is a neurobiological disorder with symptoms that include impaired social interactions and repetitive, stereotyped patterns of behavior. Around 10 percent of autistic people also have an extraordinary skill or talent such as greatly enhanced memory. Mutations in the gene for neuroligin 3, an adhesion protein that connects brain cells, have been associated with autism. One of these mutations is called R451C because the altered gene encodes a protein with an amino acid substitution: a cysteine (C) instead of an arginine (R) in position 451. In 2007, Katsuhiko Tabuchi and his colleagues introduced the R451C mutation into the neuroligin 3 gene of mice. The researchers discovered that the genetically modified mice had impaired social behavior and superior spatial learning ability. Spatial learning in mice is tested with a water maze, which consists of a small platform submerged a bit below the surface or a pool of water so it is invisible to a swimming mouse. Mice do not particularly enjoy swimming, so they try to locate the hidden platform as quickly as they can. When tested again later, they remember the platforms location by checking visual cues around the edge or the pool. How quickly they remember is a measure of their spatial learning ability. FIGURE 15.14 shows some or Tabuchis result. FIGURE 15.14 Spatial learning ability in mice. Mice with a mutation in neuroligin 3 (R451C) were tested for learning performance: as compared with unmodified (wild-type) mice. Did the modified or the unmodified mice learn the location of the platform faster in the first test?arrow_forward
- Help answer questionarrow_forwardCap, EA1, and Sap are all genes and are also proteins. For each gene, what gene product is encoded and where is the gene aka literal DNA sequence and located physically in the cell? I need help for each one cap what gene product is encoded and location Ea1 what gene product is encoded and location Sap what gene product is encoded and locationarrow_forwardfast answer plsarrow_forward
- What is dominant control mechanism of gene expression? explain the following image.arrow_forwardWhen chromatin is condensed, transcription cannot happen. Why not? RNA cannot access the promoter region of the gene DNA helicase cannot access the RNA strand RNA polymerase cannot access the DNA strand Transcription factors cannot access the termination region of the genearrow_forwardAlmost all calico cats (one is pictured in FIGURE 10.7B) are female. Why? B When this calico cat was an embryo, one of the two X chromosomes was inactivated in each of her cells. The descendants of the cells formed her adult body, which is a mosaic for expression of X chromosome genes. Black fur arises in patches where genes on the X chromosome inherited from one parent are expressed; orange fur arises in patches where genes on the X chromosome inherited from the other parent are expressed. FIGURE 10.7 Animated X chromosome inactivation.arrow_forward
- Equalizing the Expression of X Chromosome Genes in Males and Females Males have only one X chromosome and therefore only one copy of all genes on the X chromosome. Each gene is directly expressed, thus providing the basis of hemizygosity in males. Females have two X chromosomes, but one is always inactivated. Therefore, females, like males, have only one functional copy of all the genes on the X chromosome. Again, each gene must be directly expressed. Why, then, are females not considered hemizygous, and why are they not afflicted with sex-linked recessive diseases as often as males are?arrow_forwardAnimal Models: The Search for Behavior Genes You are a researcher studying an autosomal dominant neurodegenerative disorder. You have cloned the gene underlying the disorder and have found that it encodes an enzyme that is overexpressed in the neurons of individuals who have the disorder. To better understand how this enzyme causes neurodegeneration in humans, you make a strain of transgenic Drosophila whose nerve cells overexpress the enzyme. a. How might you use these transgenic flies to try to gain insight into the disease or identify drugs that might be useful in the treatment of the disease? b. Can you think of any potential limitations of this approach?arrow_forwardNeanderthal Hair Color The MC1R gene regulates pigmentation in humans (Sections 14.1 and 15.1 revisited), so loss-of-function mutations in this gene affect hair and skin color. A person with two mutated alleles for this gene makes more of the reddish melanin than the brownish melanin, resulting in red hair and pale skin. DNA extracted from two Neanderthal fossils contains a mutated MC1R allele that has not yet been found in humans. To see how the Neanderthal mutation affects the function of the MC1R gene. Carles Lalueza-Fox and her team introduced the allele into cultured monkey cells (FIGURE 26.16). FIGURE 26.16 MC1R activity in monkey cells transgenic for an unmutated MC1R gene, the Neanderthal MC1R allele, or the gene for green fluorescent protein (GFP). GFP is not related to MC1R. 1. How did MCR1 activity in monkey cells with the mutant allele differ from that in cells with the normal allele?arrow_forward
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