CH13_Answers

CH13_Answers - Raven/Johnson Biology 8e Chapter 13 1 Why is...

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Raven/Johnson Biology 8e Chapter 13 1. Why is the white-eye phenotype always observed in males carrying the white-eye allele? a. Because the trait is dominant b. Because the trait is recessive c. Because the allele is located on the X chromosome and males only have one X d. Because the allele is located on the Y chromosome and only males have Y chromosomes The correct answer is c— A. Answer a is incorrect. The white-eye gene must be recessive since heterozygous females have red eyes. The correct answer is c— B. Answer b is incorrect. The white-eye gene is recessive; however, this does not explain why it is always observed in males. The correct answer is c—Because the allele is located on the X chromosome and males only have one X C. Answer c is correct. Because the gene is located on the X chromosome, and the Y chromosome lacks most X chromosome genes, any male carrying the white-eye allele will show the phenotype. The correct answer is c— D. Answer d is incorrect. The allele is located on the X chromosome as demonstrated by the testcross. The Y chromosome does not carry many genes that are expressed. 2. An autosome is a chromosome that— a. contains genetic information to determine the sex of an organism b. determines all other traits of an organism other than sex c. is only inherited from the mother (maternal inheritance) d. has no matching chromosome within an organism’s genome The correct answer is b— A. Answer a is incorrect. The sex of an organism is determined by the sex chromosomes. The correct answer is b—determines all other traits of an organisms other than sex B. Answer b is correct. Autosomes are the chromosomes that carry the majority of genetic information that determines the overall phenotype of an organism. The sex chromosomes, in contrast, determine the sex of the organism. The correct answer is b— C. Answer c is incorrect. The autosomes are inherited from both parents. The correct answer is b— D. Answer d is incorrect. The autosomes exist as homologous pairs. 3. Sex linkage in humans occurs when— a. an allele is located on both the X and Y chromosomes b. all allele is located on the X chromosome c. an allele is located on an autosome
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Raven/Johnson Biology 8e Chapter 13 d. a phenotype is only observed in females The correct answer is b— A. Answer a is incorrect. An allele is sex-linked if it is present on only one of the sex chromosomes. Few of the genes found on the Y chromosome are expressed. The correct answer is b—an allele is located on the X chromosome B. Answer b is correct. The phenotype of genes present on the X chromosome will be observed in human males since there is not a second X available. Males cannot be heterozygous for a recessive allele located on the X chromosome. The correct answer is b—
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CH13_Answers - Raven/Johnson Biology 8e Chapter 13 1 Why is...

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