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Mutations in the TYR gene may render its enzyme product—tyrosinase—nonfunctional. Individuals homozygous for such mutations cannot make the pigment melanin. Albinism, the absence of melanin, results. Humans and many other organisms can have this phenotype (right). Mutated tyrosinase alleles are recessive when paired with the normal allele in heterozygous individuals. In the following situations, what are the probable genotypes of the father, the mother, and their children? a. Both parents have normal phenotypes; some of their children have the albino phenotype and others are unaffected. b. Both parents and children have the albino phenotype. c. The mother and three children are unaffected; the father and one child have the albino phenotype.

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Biology: The Unity and Diversity o...

15th Edition
Cecie Starr + 3 others
Publisher: Cengage Learning
ISBN: 9781337408332

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Section
BuyFindarrow_forward

Biology: The Unity and Diversity o...

15th Edition
Cecie Starr + 3 others
Publisher: Cengage Learning
ISBN: 9781337408332
Chapter 13, Problem 7GP
Textbook Problem
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Mutations in the TYR gene may render its enzyme product—tyrosinase—nonfunctional. Individuals homozygous for such mutations cannot make the pigment melanin. Albinism, the absence of melanin, results. Humans and many other organisms can have this phenotype (right). Mutated tyrosinase alleles are recessive when paired with the normal allele in heterozygous individuals. In the following situations, what are the probable genotypes of the father, the mother, and their children?

  1. a. Both parents have normal phenotypes; some of their children have the albino phenotype and others are unaffected.
  2. b. Both parents and children have the albino phenotype.
  3. c. The mother and three children are unaffected; the father and one child have the albino phenotype.

Chapter 13, Problem 7GP, Mutations in the TYR gene may render its enzyme producttyrosinasenonfunctional. Individuals

a.

Summary Introduction

To explain: The probable genotypes of father, mother, and their children when both parents have normal phenotypes: some of their children have the albino phenotype and the rest are unaffected.

Concept introduction: Albinism is a disorder common in several organisms that occur as the mutation of TYR gene. TYR gene is produced by tyrosine amino acid that is later oxidized and polymerized to produce the melanin pigment. Melanin pigment is responsible for the production of skin color, hair color, and iris color. TYR gene in its recessive condition causes albinism.  In the homologous chromosome, two genes are present in two different loci. These two genes separate and enter two different gametes independent of the other.  This process is called as law of independent assortment. During meiosis, the two copies of the same gene in the locus separate and enter gametes, so that the offspring acquires one copy of gene from each parent.

Explanation of Solution

 The TYR gene can occur in three conditions. “A” represents the dominant allele, and “a” represents recessive allele.

AA- Homozygous dominant. Normal individual

Aa- Heterozygous. Normal individual.

aa- Homozygous recessive. Albino.

If both parents are heterozygous Aa × Aa...

b.

Summary Introduction

To explain: The probable genotypes of father, mother, and their children when both parents and children have the albino phenotype.

Concept introduction: Albinism is a disorder common in several organisms that occur as the mutation of TYR gene. TYR gene is produced by tyrosine amino acid that is later oxidized and polymerized to produce the melanin pigment. Melanin pigment is responsible for the production of skin color, hair color, and iris color. TYR gene in its recessive condition causes albinism.  In the homologous chromosome, two genes are present in two different loci. These two genes separate and enter two different gametes independent of the other.  This process is called as law of independent assortment. During meiosis, the two copies of the same gene in the locus separate and enter gametes, so that the offspring acquires one copy of gene from each parent.

c.

Summary Introduction

To explain: The probable genotypes of father, mother, and their children when the mother and three children are unaffected: the father and one child have the albino phenotype.

Concept introduction: Albinism is a disorder common in several organisms that occur as the mutation of TYR gene. TYR gene is produced by tyrosine amino acid that is later oxidized and polymerized to produce the melanin pigment. Melanin pigment is responsible for the production of skin color, hair color, and iris color. TYR gene in its recessive condition causes albinism.  In the homologous chromosome, two genes are present in two different loci. These two genes separate and enter two different gametes independent of the other.  This process is called as law of independent assortment. During meiosis, the two copies of the same gene in the locus separate and enter gametes, so that the offspring acquires one copy of gene from each parent.

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