Genetics: From Genes to Genomes
6th Edition
ISBN: 9781259700903
Author: Leland Hartwell Dr., Michael L. Goldberg Professor Dr., Janice Fischer, Leroy Hood Dr.
Publisher: McGraw-Hill Education
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Chapter 15, Problem 18P
Plant 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 |
|
| a. | Describe a cross generating hybrid corn seed that would grow into fertile (self-fertilizing) plants. (Farmers planting hybrid seed want fertile plants because corn kernels result from fertilized ovules.) |
| b | One of the historical challenges in the commercialization of hybrid corn produced through CMS was the maintenance of strains with CMS mitochondria: How could the seed companies keep producing male sterile corn plants if these plants never themselves produced pollen? Suggest a strategy by which the seed companies could continue to obtain male sterile plants every breeding season. |
| c. | Are there any potential disadvantages to the use of hybrid corn? If so, what issues might arise? |
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You are studying a plant with tissue comprising both green and white sectors. You wish to decide whether this phenomenon is due (1) to a chloroplast mutation of the type considered in this chapter or (2) to a dominant nuclear mutation that inhibits chlorophyll production and is present only in certain tissue layers of the plant as a mosaic. Outline the experimental approach that you would use to resolve this problem.
Plant 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.
In a species of tree, seed color is determined by four independently
assorting genes: A, B, C, and D. The recessive alleles of each of these genes (a, b,
C, and d) produce abnormal enzymes that cannot catalyze a reaction in the
biosynthetic pathway for seed pigment.
This pathway is diagrammed as follows:
A
White precursor
Yellow ----Orange----- Red
---
Blue
When both red and blue pigments are present, the seeds are purple. Trees with
the genotypes Aa Bb Cc Dd and Aa Bb Cc dd were crossed.
(a) What color are the seeds in these two parental genotypes?
(b) What proportion of the offspring from the cross will have white seeds?
(c) Determine the relative proportions of red, white, and blue offspring from the
cross.
Chapter 15 Solutions
Genetics: From Genes to Genomes
Ch. 15 - Match each numbered item with the most closely...Ch. 15 - Assuming human cells have on average 1000...Ch. 15 - Reverse translation is a term given to the process...Ch. 15 - The human nuclear genome encodes tRNAs with 32...Ch. 15 - The human mitochondrial genome includes no genes...Ch. 15 - How do you know if the halibut you purchased at...Ch. 15 - Is each of these statements true of chloroplast or...Ch. 15 - Suppose you are characterizing the DNA of a...Ch. 15 - An example of a gene-targeting DNA plasmid vector...Ch. 15 - Which of the following characteristics of...
Ch. 15 - The Saccharomyces cerevisiae nuclear gene ARG8...Ch. 15 - The so-called hypervariable regions HV1 and HV2 of...Ch. 15 - Suppose a new mutation arises in a mitochondrial...Ch. 15 - Describe at least two ways in which the...Ch. 15 - Why are severe mitochondrial or chloroplast gene...Ch. 15 - Suppose you are examining a newly found plant...Ch. 15 - A form of male sterility in corn is inherited...Ch. 15 - Plant breeders have long appreciated the...Ch. 15 - A mutant haploid strain of Saccharomyces...Ch. 15 - Prob. 20PCh. 15 - What characteristics in a human pedigree suggest a...Ch. 15 - The first person in the family represented by the...Ch. 15 - In 1988, neurologists in Australia reported the...Ch. 15 - If you were a genetic counselor and had a patient...Ch. 15 - Kearns-Sayre syndrome KSS, Pearson syndrome, and...Ch. 15 - Many clinically relevant mitochondrial diseases...Ch. 15 - Leigh syndrome is characterized by psychomotor...Ch. 15 - All mutations in mitochondrial genes ultimately...Ch. 15 - How could researchers have determined that the...
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