Concepts of Genetics (12th Edition)
12th Edition
ISBN: 9780134604718
Author: William S. Klug, Michael R. Cummings, Charlotte A. Spencer, Michael A. Palladino, Darrell Killian
Publisher: PEARSON
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Chapter 14, Problem 34ESP
Deep in a previously unexplored South American rain forest, a plant species was discovered with true-breeding varieties whose flowers were pink, rose, orange, or purple. A very astute plant geneticist made a single cross, carried to the F2 generation, as shown:
Based solely on these data, he proposed both a mode of inheritance for flower pigmentation and a biochemical pathway for the synthesis of these pigments.
Carefully study the data. Create a hypothesis of your own to explain the mode of inheritance. Then propose a biochemical pathway consistent with your hypothesis. How could you test the hypothesis by making other crosses?
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Students have asked these similar questions
A paper hypothesizes that white flowers are unable to produce anthocyanins (purple pigments) because they lack a functional “A” protein. However, it is also possible that an unknown gene is responsible for the lack of anthocyanins. Now that they have isolated DNA sequences of the “A” allele, design an experiment to use these DNA sequences to distinguish between these two hypotheses.
During the course of a research project you generate a gene knockout line in Arabidopsis thaliana to study the function of a gene you believe plays a crucial role in cellular metabolism. You note that the initial transformants are a bit smaller than normal. In subsequent crosses you are unable to isolate homozygotes for the knockout allele. Heterozygotes in subsequent generation are still a bit smaller than the homozygous wild type plants. Explain what is happening.
The wild-type (normal) fruit fly, Drosophila melanogaster, has straight wings and long
bristles. Mutant strains have been isolated with either curled wings or short bristles.
The genes representing these two mutant traits are located on separate
chromosomes. Carefully examine the data from the five crosses below. (a) For each
mutation, determine whether it is dominant or recessive. In each case, identify
which crosses support your answer; and (b) define gene symbols and determine the
genotypes of the parents for each cross.
Cross
1. straight, short X
straight, short
2. straight, long X
straight, long
3. curled, long X
straight, short
4. straight, short X
straight, short
5. curled, short X
straight, short
straight
wings,
long
bristles
30
120
40
40
20
Number of Progeny
straight
curled
wings, wings,
short
long
bristles
bristles
90
10
0
40
120
60
40
40
0
20
curled
wings,
short
bristles
30
0
40
0
60
Chapter 14 Solutions
Concepts of Genetics (12th Edition)
Ch. 14 - Prob. 1NSTCh. 14 - A series of mutations in the bacterium Salmonella...Ch. 14 - HbS results from the substitution of valine for...Ch. 14 - Given that a faulty ribosomal protein is the...Ch. 14 - A couple with a child affected with DBA undergoes...Ch. 14 - Prob. 3CSCh. 14 - HOW DO WE KNOW? In this chapter, we focused on the...Ch. 14 - CONCEPT QUESTION Review the Chapter Concepts list...Ch. 14 - Contrast the roles of tRNA and mRNA during...Ch. 14 - Francis Crick proposed the adaptor hypothesis for...
Ch. 14 - During translation, what molecule bears the codon?...Ch. 14 - The chain of eukaryotic hemoglobin is composed of...Ch. 14 - Assuming that each nucleotide in an mRNA is 0.34...Ch. 14 - Summarize the steps involved in charging tRNAs...Ch. 14 - To carry out its role, each transfer RNA requires...Ch. 14 - What are isoaccepting tRNAs? Assuming that there...Ch. 14 - When a codon in an mRNA with the sequence 5-UAA-3...Ch. 14 - Discuss the potential difficulties of designing a...Ch. 14 - Prob. 13PDQCh. 14 - Prob. 14PDQCh. 14 - The synthesis of flower pigments is known to be...Ch. 14 - The study of biochemical mutants in organisms such...Ch. 14 - Explain why the one-gene: one-enzyme concept is...Ch. 14 - Why is an alteration of electrophoretic mobility...Ch. 14 - Prob. 19PDQCh. 14 - Prob. 20PDQCh. 14 - Prob. 21PDQCh. 14 - Prob. 22PDQCh. 14 - Several amino acid substitutions in the and ...Ch. 14 - Define and compare the four levels of protein...Ch. 14 - What are the two common types of protein secondary...Ch. 14 - How do covalent disulfide bonds, hydrogen bonds...Ch. 14 - Prob. 27PDQCh. 14 - List three different types of posttranslational...Ch. 14 - Prob. 29PDQCh. 14 - How does an enzyme function? Why are enzymes...Ch. 14 - Prob. 31PDQCh. 14 - Three independently assorting genes (A, B, and C)...Ch. 14 - How would the results vary in cross (a) of Problem...Ch. 14 - Deep in a previously unexplored South American...Ch. 14 - Many antibiotics are effective as drugs to fight...Ch. 14 - The flow of genetic information from DNA to...Ch. 14 - Prob. 37ESP
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- The wild-type (normal) fruit fly, Drosophila melanogaster, has straight wings and long bristles. Mutant strains have been isolated with either curled wings or short bristles. The genes representing these two mutant traits are located on separate chromosomes. Carefully examine the data from the five crosses below. (a) For each mutation, determine whether it is dominant or recessive. In each case, identify which crosses support your answer; and (b) define gene symbols and determine the genotypes of the parents for each cross.arrow_forwardThe synthesis of flower pigments is known to be dependent on enzymatically controlled biosynthetic pathways. For the crosses shown here, postulate the role of mutant genes and their products in producing the observed phenotypes: (a) P1: white strain A * white strain B F1: all purple F2: 9/16 purple: 7/16 white (b) P1: white * pink F1: all purple F2: 9/16 purple: 3/16 pink: 4/16 whitearrow_forwardTwo plants with white flowers, each from true-breeding strains, were crossed. All the F1 plants had red flowers. When these F1 plants were intercrossed, they produced an F2 consisting of 177 plants with red flowers and 142 with white flowers. (a) Propose an explanation for the inheritance of flower color in this plant species. (b) Propose a biochemical pathway for flower pigmentation and indicate which genes control which steps in this pathway.arrow_forward
- In a study, an undergraduate student discovered a new enzyme involved in the metabolism of serotonin. This enzyme is made up of 3 subunits of the same protein. To characterize this enzyme, the student used genetic approaches to induce mutations in the coding region of the gene that codes for this protein and performed crosses to measure the effects of genotypes on enzyme activity. A) Indicate directly in the diagram (via a bar graph) the predicted relationship between genotype and enzyme activity. (Al represents the wild-type allele, A2 represents the mutant allele). A2A2 A1A2 A1Α1 B) Explain the reasoning for your prediction. Enzyme Activityarrow_forwardYour task will ultimately be to generate a hypothesis and test this hypothesis using a chi square test. There are four possible phenotypes for these kernels:Purple and Smooth Purple and Shrunken Yellow and Smooth Yellow and Shrunken The purple colour results from the formation of a purple pigment in the skin of the kernel. The gene locus for the colour trait is designated “R”. The wrinkled phenotype arises from a decrease in the amount starch produced within the kernel. The gene locus for the texture trait is designated “S”. Create a Punnett square for this cross and present the expected phenotypic ratio. Present the results in a table as dihybrids and determine the observed phenotypic ratio of purple/smooth to purple/shrunken to yellow/smooth to yellow/shrunken. Consider the plant as a whole rather than the individual cobs. Generate a null hypothesis and perform a chi square test on the data. Report the equation used, the chi square value, the degrees of freedom, and the resulting…arrow_forwardSome sweet-pea plants have purple flowers and others have white flowers. A homozygous variety of sweet pea that has purple flowers is crossed with a homozygous variety that has white flowers. All the F1 have purple flowers. When these F1 self-fertilize, the F2 appear in a ratio of 916 purple to 716 white. a. Give genotypes for the purple and white flowers in these crosses. b. Draw a hypothetical biochemical pathway to explain the production of purple and white flowers in sweet peasarrow_forward
- The data set attached presents the results of a testcross using female flies heterozygous for three traits and male flies, which are homozygous recessive. For simplicity, mutant alleles are shown with letters a, b, and c and wildtype alleles are indicated by a “+” symbol. For this part of the report do the following in order: a) Determine the gene order (which gene is in the middle?)d) Construct a genetic map for the three genes, including the map distances between them. Clearly indicate the logic you followed and show all your calculations. Include the full distance calculations for the two most distanced genes (do not just add the other 2 distances). Ensure the work is neat and clear and does not contain spelling or grammatical errors so that it is understandable. Make sure to double check the solution provided.arrow_forwardPlant breeders have long appreciated the phenomenon called hybrid vigor or heterosis, in which hybrids formed between two inbred strains have increased vigor and crop yield relative to the two parental strains. Starting in the 1930s, seed companies exploited the cytoplasmic male sterility (CMS) phenomenon in corn that was described in Problem 17 so that they could cheaply produce hybrid corn seed to sell to farmers. This type of CMS is caused by mutant mitochondrial genomes that prevent pollen formation. a. How would CMS aid seed companies in producing hybrid corn seed? Dominant Rf alleles of a nuclear gene called Restorer suppress the CMS phenotype, so that Rf- containing plants with mutant mitochondrial genomes are male fertile.arrow_forwardConsider two maize plants:a. Genotype C/c m ; Ac/Ac+, where cm is an unstable allele caused by a Ds insertionb. Genotype C/c m, where cm is an unstable allele caused by Ac insertionWhat phenotypes would be produced and in what proportions when (1) each plant is crossed with a basepair-substitution mutant c/c and (2) the plant in part a is crossed with the plant in part b? Assume that Ac and c are unlinked, that the chromosome-breakage frequency is negligible, and that mutant c /C is Ac+.arrow_forward
- Consider the first category of test-cross offspring shown in figure 8.2 (+b, LS). Consider also that the parents of the heterozygous female flies in the test cross had the following genotypes: bb, SS, and +, LL. A. What would be the physical phenotype of these flies? B. If PC was conducted with the DNA of one of these flies using the primers for the molecular marker, what would be the appearance of the bands on an electrophoresis gel with the PC products? C. If the gene for black body and the locus for the molecular marker (L long or S short) were unlinked, what proportion of the test-cross progeny would be black flies that are heterozygous for the molecular marker? What proportion would be flies with normal body color, which are homozygous for one form of the molecular marker? D. If the gene for black body and the locus for the molecular marker were linked, how would the proportion of flies be different?arrow_forwardIn the early 1990s, Carolyn Napoli and her colleagues were working on petunias, attempting to genetically engineer a variety with dark purple petals by introducing numerous copies of a gene that encodes purple pigment in the flower petals . Their thinking was that extra copies of the gene would cause more purple pigment to be produced and would result in a petunia with an even darker hue of purple. However, much to their surprise, many of the plants carrying extra copies of the purple gene were completely white or had only patches of color. Molecular analysis revealed that the amount of mRNA produced by the purple gene was reduced 50-fold in the engineered plants compared with wild-type plants. Somehow, the introduction of extra copies of the purple gene silenced both the introduced copies and the plant’s own purple genes. Provide a possible explanation for how the introduction of numerous copies of the purple gene silenced all copies of the purple gene.arrow_forwardConsider the first category of test-cross offspring shown in figure 8.2 (+b, LS). Consider also that the parents of the heterozygous female flies in the test cross had the following genotypes: bb, SS, and +, LL. A. What would be the physical phenotype of these flies? B. If PCR was conducted with the DNA of one of these flies using the primers for the molecular marker, what would be the appearance of the bands on an electrophoresis gel with the PCR products? C. If the gene for black body and the locus for the molecular marker (L long or S short) were unlinked, what proportion of the test-cross progeny would be black flies that are heterozygous for the molecular marker? What proportion would be flies with normal body color, which are homozygous for one form of the molecular marker? D. If the gene for black body and the locus for the molecular marker were linked, how would the proportion of flies be different?arrow_forward
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