Essentials of Genetics (9th Edition) - Standalone book
9th Edition
ISBN: 9780134047799
Author: William S. Klug, Michael R. Cummings, Charlotte A. Spencer, Michael A. Palladino
Publisher: PEARSON
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Chapter 22, Problem 15PDQ
One of the first Mendelian traits identified in humans was a dominant condition known as brachydactyly. This gene causes an abnormal shortening of the fingers or toes (or both). At the time, some researchers thought that the dominant trait would spread until 75 percent of the population would be affected (because the
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Albinism is a recessive trait in humans.A geneticist studies a series of families in which both parents have normal pigmentation and at least one child has albinism. The geneticist reasons that both parents in these families must be heterozygotes and that albinism should appear in 14 of their children. To his surprise, the geneticist finds that the frequency of albinism among the children of these families is significantly greater than 14. Can you think of an explanation for the higher-than-expected frequency of albinism among these families?
Albinism is a recessive trait in humans . A geneticist studies a series of families in which both parents havenormal pigmentation and at least one child has albinism. The geneticist reasons that both parents in these families must be heterozygotes and that albinism should appear in 14 of their children. To his surprise, the geneticist finds that the frequency of albinism among the children of these families is significantly greater than 14. Can you think of an explanation for the higher-than-expected frequency of albinism among these families?
Albinism is a recessive trait in humans. A geneticist studies a series of families in which both parents are normal and at least one child has albinism. The geneticist reasons that both parents in these families must be heterozygotes and that albinism should appear in 1/4 of the children of these families. To his surprise, the geneticist finds that the frequency of albinism among the children of these families is considerably greater than 1/4. Can you think of an explanation for the higher than-expected frequency of albinism among these families ?
Chapter 22 Solutions
Essentials of Genetics (9th Edition) - Standalone book
Ch. 22 - CASE STUDY |An unexpected outcome A newborn...Ch. 22 - CASE STUDY |Anunexpected outcome A newborn...Ch. 22 - CASE STUDY|An unexpected outcome A newborn...Ch. 22 - HOW DO WE KNOW? Population geneticists study...Ch. 22 - Review the Chapter Concepts on page 441. All these...Ch. 22 -
3. Price et al. (1999. J. Bacteriol. 181:...Ch. 22 -
4. The genetic difference between two Drosophila...Ch. 22 - The use of nucleotide sequence data to measure...Ch. 22 - Calculate the frequencies of the AA, Aa, and aa...Ch. 22 - Prob. 7PDQ
Ch. 22 -
8. What must be assumed in order to validate the...Ch. 22 - In a population where only the total number of...Ch. 22 -
10. If 4 percent of a population in equilibrium...Ch. 22 -
11. Consider a population in which the frequency...Ch. 22 - If the initial allele frequencies are p = 0.5 and...Ch. 22 -
13. Under what circumstances might a lethal...Ch. 22 - Assume that a recessive autosomal disorder occurs...Ch. 22 -
15. One of the first Mendelian traits identified...Ch. 22 -
16. Describe how populations with substantial...Ch. 22 - Achondroplasia is a dominant trait that causes a...Ch. 22 -
18. A recent study examining the mutation rates...Ch. 22 - A form of dwarfism known as Ellis–van Creveld...Ch. 22 -
20. List the barriers that prevent interbreeding...Ch. 22 - What are the two groups of reproductive isolating...Ch. 22 - Prob. 22PDQCh. 22 -
23. In a recent study of cichlid fish inhabiting...Ch. 22 - What genetic changes take place during speciation?Ch. 22 - Some critics have warned that the use of gene...Ch. 22 - Comparisons of Neanderthal mitochondrial DNA with...
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- You are studying the genetics of a newly discovered small animal. You note that most of the population is black in colour but about 1/4 of them are white. You have determined that there is a gene (B) that produces an enzyme that converts a pigment molecule to produce the Black colour. There are 2 alleles of this gene - the dominant B and the recessive b. DNA analysis shows that black individuals have either a BB or Bb genotype and that white individuals have a bb phenotype. However, after extensive DNA analysis, you have discovered that a small percentage of White individuals have either a BB or Bb genotype. Describe two reasons (at a molecular level) that could explain this apparent anomaly. There wasn't a mistake in analysis! These individuals did have a BB or Bb genotype but a white phenotype.arrow_forwardSickle cell anemia is caused by a recessive allele at a single gene. As we discussed in class, being a homozygote for the sickle cell allele is almost always lethal, but heterozygotes tend to be resistant against malaria although they have a mild form of anemia. Because of this heterozygote advantage, the allele for sickle cell anemia has a frequency of more than 10% in some human populations. How would present allele frequencies of the sickle cell allele change, if there was no heterozygote advantage or disadvantage (that is, that heterozygotes would be identical to ‘normal’ homozygotes – no malaria resistance, no anemia)? How would the change in sickle cell allele frequencies compare to scenario a (extirpation of malaria)arrow_forwardAs seen in the photo, Labradors come in three colors-- black, brown and yellow. What is the genetic basis for these different coat colors? One gene produces melanin, a pigment which is deposited in the dog's fur and makes the color dark. With this gene, allele B (black) is dominant to allele b. Only in the case of a recessive homozygote (bb) will the dog's phenotype be brown. The regulatory gene is separate from the melanin gene but it acts as a switch, either turning the melanin gene on or turning it off. Allele E is dominant and allows for the melanin to be deposited in the dog's fur ("on" switch), but if the switch gene is a recessive homozygote, the melanin is blocked ("off" switch) and a yellow dog is the result! 1. Two other Labradors mate and produce puppies. Their genotypes are Bbee and BbEe. What color are each parent and what are the phenotypic rations of their offspring in the F1 Generation? Show your work with a Punnett square.arrow_forward
- As seen in the photo, Labradors come in three colors-- black, brown and yellow. What is the genetic basis for these different coat colors? One gene produces melanin, a pigment which is deposited in the dog's fur and makes the color dark. With this gene, allele B (black) is dominant to allele b. Only in the case of a recessive homozygote (bb) will the dog's phenotype be brown. The regulatory gene is separate from the melanin gene but it acts as a switch, either turning the melanin gene on or turning it off. Allele E is dominant and allows for the melanin to be deposited in the dog's fur ("on" switch), but if the switch gene is a recessive homozygote, the melanin is blocked ("off" switch) and a yellow dog is the result! Review the information on Labrador retrievers above. What are the phenotypic ratios of the F1 generation offspring of two dihybrids? Make sure to match the numbers with coat colors (e.g, which number in the ration goes with which color). Use a Punnett square to…arrow_forwardA curious polymorphism in human populations has to do with the ability to curl up the sides of the tongue to make a trough (“tongue rolling”). Some people can do this trick, and others simply cannot. Hence, it is an example of a dimorphism. Its significance is a complete mystery. In one family, a boy was unable to roll his tongue but, to his great chagrin, his sister could. Furthermore, both his parents were rollers, and so were both grandfathers, one paternal uncle, and one paternal aunt. One paternal aunt, one paternal uncle, and one maternal uncle could not roll their tongues.a. Draw the pedigree for this family, defining your symbols clearly, and deduce the genotypes of as many individual members as possible.b. The pedigree that you drew is typical of the inheritance of tongue rolling and led geneticists to come up with the inheritance mechanism that no doubt you came up with. However, in a study of 33 pairs of identical twins, both members of 18 pairs could roll, neither member…arrow_forwardB B BB Bb b Bb bb Brown rabbits have the genotype BB or Bb. White rabbits have the genotype bb. If two brown rabbits, with the genotypes seen in the Punnett square above, have baby rabbits, what is the probability that the baby rabbits will also be brown? A B) 50% 75% D) 100% 5) According to Mendel's is why gametes have half the usual number of chromosomes. one copy of a gene is passed randomly from each parent to their offspring. This Sign out acerarrow_forward
- Albinism is a recessive trait in humans. A geneticist studies a series of families in which both parents are normal and at least one child has albinism. The geneticist reasons that both parents in these families must be heterozygotes and that albinism should appear in ¼ of the children of these families. To his surprise, the geneticist finds that the frequency of albinism among the children of these families is considerably greater than ¼. There is no evidence that normal pigmentation exhibits incomplete penetrance. Can you think of an explanation for the higher-than-expected frequency of albinism among these families?arrow_forwardAlbinism is a recessive trait in humans. A geneticist studies families in which both parents are normal and at least one child has albinism. The geneticist reasons that both parents in these families must be heterozygous and the albinism should appear in 1⁄4 of the children of these families. To his surprise, the geneticist finds the frequency of albinism trait is quite high. As a consultant, can you suggest an explanation for the higher expected frequency of albinisms in these families?arrow_forwardOften geneticists want to change one allele in an outcrossing organism while keeping the rest of the genome the same. For example, they might wish to take a specially designed stock of flies and alter the eye color from red to white. Suppose that the white-eye allele is dominant, meaning that flies with one or two white-eye alleles will have white eyes. One procedure used is to take a white-eyed fly and cross it with the red-eyed stock. The whiteeyed offspring are then considered to be the first generation, and are crossed with the red-eyed stock. Their white-eyed offspring are considered to be the second generation, and are again crossed with the red-eyed stock, and so forth. The special red-eyed stock is homozygous for the desirable allele A at some other locus, but the white-eyed fly is homozygous for the inferior a allele at that locus. What fraction of flies will have the a allele (at the second locus) after one generation?arrow_forward
- A common misconception of evolution is that it should naturally eliminate "harmful" alleles/mutations if they do not assist survival or reproduction. Explain why this is inaccurate and how these "harmful" mendelian alleles persist within the human genome. In your response, give an example of a mendelian allele that causes a "harmful" genetic disease that does not appear to have a beneficial componentarrow_forwardOften geneticists want to change one allele in an outcrossing organism while keeping the rest of the genome the same. For example, they might wish to take a specially designed stock of flies and alter the eye color from red to white. Suppose that the white-eye allele is dominant, meaning that flies with one or two white-eye alleles will have white eyes. One procedure used is to take a white-eyed fly and cross it with the red-eyed stock. The whiteeyed offspring are then considered to be the first generation, and are crossed with the red-eyed stock. Their white-eyed offspring are considered to be the second generation, and are again crossed with the red-eyed stock, and so forth. The special red-eyed stock is homozygous for the desirable allele A at some other locus, but the white-eyed fly is homozygous for the inferior a allele at that locus. What is the genotype at the eye color locus in the second and subsequent generations?arrow_forwardOften geneticists want to change one allele in an outcrossing organism while keeping the rest of the genome the same. For example, they might wish to take a specially designed stock of flies and alter the eye color from red to white. Suppose that the white-eye allele is dominant, meaning that flies with one or two white-eye alleles will have white eyes. One procedure used is to take a white-eyed fly and cross it with the red-eyed stock. The whiteeyed offspring are then considered to be the first generation, and are crossed with the red-eyed stock. Their white-eyed offspring are considered to be the second generation, and are again crossed with the red-eyed stock, and so forth. The special red-eyed stock is homozygous for the desirable allele A at some other locus, but the white-eyed fly is homozygous for the inferior a allele at that locus. What fraction of flies will have the a allele (at the second locus) after t generations?arrow_forward
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How to solve genetics probability problems; Author: Shomu's Biology;https://www.youtube.com/watch?v=R0yjfb1ooUs;License: Standard YouTube License, CC-BY
Beyond Mendelian Genetics: Complex Patterns of Inheritance; Author: Professor Dave Explains;https://www.youtube.com/watch?v=-EmvmBuK-B8;License: Standard YouTube License, CC-BY