Biology: The Dynamic Science (MindTap Course List)
4th Edition
ISBN: 9781305389892
Author: Peter J. Russell, Paul E. Hertz, Beverly McMillan
Publisher: Cengage Learning
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Textbook Question
Chapter 12, Problem 3ITD
Half of the world’s population eats rice at least twice a day. Much of this rice is grown in flooded conditions, and different strains of rice are tolerant (survive) or intolerant (die) under these conditions. Rice breeders used genetic crosses to test whether tolerance to flooding is a dominant trait. Researchers used three true-breeding flood-tolerant strains, FR143, BKNFR, and Kurk, and two true-breeding flood- intolerant strains, IR42 and NB, in the crosses. Results were obtained from three sets of crosses and are reported in the Table below:
Results of cross of F1 to tolerant parent: F1 plants were crossed with the tolerant parent of the cross.
| Number of Plants | |||
| Progeny Analyzed from Intolerant × Tolerant Cross | Alive | Dead | Total |
| 1. F2 results of cross: | |||
| IR42 × FR13A | 187 | 77 | 264 |
| IR42 × BKNFR | 192 | 73 | 265 |
| NB × Kurk | 142 | 52 | 195 |
| 2. Results of cross of F1 to intolerant parent: | |||
| (F1 of IR42 × FR13A) × IR42 | 14 | 17 | 31 |
| (F1 of IR42 × BKNFR) × IR42 | 15 | 10 | 25 |
| (F1 of NB × Kurk) × NB | 21 | 35 | 56 |
| 3. Results of cross of F1 to tolerant parent: | |||
| (F1 of IR42 × FR13A) × FR13A | 31 | 0 | 31 |
| (F1 of IR42 × BKNFR) × BKNFR | 28 | 0 | 28 |
| (F1 of NB × Kurk) × Kurk | 40 | 0 | 40 |
Do the data support the hypothesis that the tolerance trait is dominant? Justify your conclusion by explaining the results from each of the three sets of crosses in terms of genotypes and
Source: T. Setter et al. 1997. Physiology and genetics of submergence tolerance in rice. Annals of
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A very large population of rabbits has been allowed to breed randomly in a laboratory research program. The rabbits vary in their coat colour, which is either gray or
black. After many generations, 25% of the rabbits display a recessive phenotype for gray coat colour (aa), the same percentage as at the beginning of the breeding
program. The other 75% of the rabbits show the dominant black coat phenotype, with heterozygotes (Aa) indistinguishable from the homozygous dominants (AA)
What is a reasonable conclusion explaining the fact that the frequency of the recessive trait (aa) has not changed over time?
a. There has been sexual selection favouring allele a
b.
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C. The population is undergoing genetic drift
d.
The genotype AA is lethal
2) The year is 2050. The climate has continued to warm. Areas in northern Canada and Alaska are without snow or ice; the average annual temperature has risen and previously snow-covered areas are now shrub land and some temperate forests. What effect would such a climatic change have on the gene pool of the rabbits? All BUT ONE could apply.
A) The allelic frequency has most likely shifted to 85% GG and 15% gg.
B) The dominant allele in the gene pool would become G, the previously rare allele.
C) The allele for white, g, would be scarce and perhaps nonexistent in the population.
D) White rabbits would be at a disadvantage in terms of camouflage and would likely fall prey to predators.
A mountain region has a population of 5,000 mountain goats. You score these animals for the R locus and find that this locus has two alleles, R (dominant) and r (recessive). 3200 individuals are homozygous dominant, 1,600 are heterozygous, and 200 are homozygous recessive.
A deadly virus infects all of the RR mountain goats in the population (above), killing all individuals of this genotype and leaving the population with only the rr and Rr mountain goats.
a) Calculate the new allele frequencies for this population. Show your work.
b) Calculate the new (observed) genotypic frequencies for this population. Show your work.
c) Does this population still appear to be at H-W equilibrium? Why or why not? (You do not need to analyze this statistically).
Chapter 12 Solutions
Biology: The Dynamic Science (MindTap Course List)
Ch. 12.1 - Two pairs of traits are segregating in a cross....Ch. 12.1 - If, instead, the four phenotypes in question 1...Ch. 12.2 - Palomino horses have a golden coat color, with a...Ch. 12.2 - A true-breeding rabbit with agouti (mottled,...Ch. 12 - The dominant C allele of a gene that controls...Ch. 12 - In peas, the allele Le produces tall plants and...Ch. 12 - Prob. 3TYKCh. 12 - What genotypes, and in what frequencies, will be...Ch. 12 - In addition to the two genes in problem 4, assume...Ch. 12 - Prob. 6TYK
Ch. 12 - In cats, the genotype AA produces tabby fur color;...Ch. 12 - Prob. 8TYKCh. 12 - The ability of humans to taste the bitter chemical...Ch. 12 - A man is homozygous dominant for alleles at 10...Ch. 12 - In guinea pigs, an allele for rough fur (R) is...Ch. 12 - Prob. 12TYKCh. 12 - Some recessive alleles have such a detrimental...Ch. 12 - In chickens, feathered legs are produced by a...Ch. 12 - A mix-up in a hospital ward caused a mother with O...Ch. 12 - Having malformed hands with shortened fingers is a...Ch. 12 - Prob. 17TYKCh. 12 - Design an Experiment Imagine that you are a...Ch. 12 - Prob. 19TYKCh. 12 - Prob. 1ITDCh. 12 - Prob. 2ITDCh. 12 - Half of the worlds population eats rice at least...
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