Chapter 3, Problem 1P

For each of the terms in the left column, choose the best matching phrase in the right column.

a. epistasis	1. one gene affecting more than one phenotype
b. nucleotide	2. part of a gene that does not contain protein coding information
c. conditional lethal	3. both parental phenotypes are expressed in the F hybrids
d. permissive condition	4. a heritable change in a gene
e. reduced penetrance	5. genes whose alleles alter phenotypes produced by the action of other genes
f. multifactorial trait	6. less than 100% of the individuals possessing a particular genotype express it in their phenotype
g. incomplete dominance	7. environmental condition that allows conditional lethals to live
h. codominance	8. a trait produced by the interaction of alleles of at least two genes or from interactions between gene and environment
i. mutation	9. individuals with the same genotype have related phenotypes that vary in intensity
j. pleiotropy	10. a genotype that is lethal in some situations (for example, high temperature) but viable in others
k. variable expressivity	11. the heterozygote resembles neither homozygote

Summary Introduction

a.

To determine:

The phrase that describes “epistasis” among the options given below.

1. one gene affecting more than one phenotype

2. part of a gene that does not contain protein-coding information

3. both parental phenotypes are expressed in the F hybrids

4. a heritable change in a gene

5. genes whose alleles alter phenotypes produced by the the action of other genes

6. less than 100% of the individuals possessing a particular genotype express it in their phenotype

7. environmental condition that allows conditional lethal to live

8. a trait produced by the interaction of alleles of at least two genes or from interactions between gene and environment

9. individuals with the same genotype have related phenotypes that vary in intensity

10. a genotype that is lethal in some situations (for example, high temperature) but viable in others

11. the heterozygote resembles neither homozygote

Introduction:

When the phenotype of a particular gene locus is masked by another locus of gene, this situation is called epistasis.

Answer to Problem 1P

Correct answer:

Epistasis: part of a gene that does not contain protein-coding information

Explanation of Solution

Epistasis is a phenomenon in which the locus of one gene can mask the phenotype of another gene locus. The gene that masks the effects of another gene is known as an epistatic gene.

Summary Introduction

b.

To determine:

The phrase that describes “nucleotide” among the options given below.

1. one gene affecting more than one phenotype

2. part of a gene that does not contain protein-coding information

3. both parental phenotypes are expressed in the F hybrids

4. a heritable change in a gene

5. genes whose alleles alter phenotypes produced by the action of other genes

6. less than 100% of the individuals possessing a particular genotype express it in their phenotype

7. environmental condition that allows conditional lethal to live

8. a trait produced by the interaction of alleles of at least two genes or from interactions between gene and environment

9. individuals with the same genotype have related phenotypes that vary in intensity

10. a genotype that is lethal in some situations (for example, high temperature) but viable in others

11. the heterozygote resembles neither homozygote

Introduction:

Nucleotides are made up of pentose sugar, nitrogenous bases, and phosphate group.

Answer to Problem 1P

Correct answer:

Nucleotide: Genes whose alleles alter phenotypes produced by the action of other genes

Explanation of Solution

Nucleotide are regarded as the building blocks of nucleic acid. They can form either deoxyribose nucleic acid or ribonucleic acid.

Summary Introduction

c.

To determine:

The phrase that describes “conditional lethal” among the options given below.

1. one gene affecting more than one phenotype

2. part of a gene that does not contain protein coding information

3. both parental phenotypes are expressed in the F hybrids

4. a heritable change in a gene

5. genes whose alleles alter phenotypes produced by the action of other genes

6. less than 100% of the individuals possessing a particular genotype express it in their phenotype

7. environmental condition that allows conditional lethals to live

8. a trait produced by the interaction of alleles of at least two genes or from interactions between gene and environment

9. individuals with the same genotype have related phenotypes that vary in intensity

10. a genotype that is lethal in some situations (for example, high temperature) but viable in others

11. the heterozygote resembles neither homozygote

Introduction:

When in certain situation, alleles become lethal, that condition is called conditional lethal.

Answer to Problem 1P

Correct answer:

Conditional lethal: A genotype that is lethal in some situations (for example, high temperature) but viable in others.

Explanation of Solution

A condition in which circumstances makes the alleles lethal is said to be conditional lethal. For example, some animals contain lethal condition alleles for low temperature. When these animals are exposed to low temperature than they may die.

Summary Introduction

d.

To determine:

The phrase that describes “permissive condition” among the options given below.

1. one gene affecting more than one phenotype

2. part of a gene that does not contain protein coding information

3. both parental phenotypes are expressed in the F hybrids

4. a heritable change in a gene

5. genes whose alleles alter phenotypes produced by the action of other genes

6. less than 100% of the individuals possessing a particular genotype express it in their phenotype

7. environmental condition that allows conditional lethals to live

8. a trait produced by the interaction of alleles of at least two genes or from interactions between gene and environment

9. individuals with the same genotype have related phenotypes that vary in intensity

10. a genotype that is lethal in some situations (for example, high temperature) but viable in others

11. the heterozygote resembles neither homozygote

Introduction:

When mutatnt and lethal allele can grow or survive in a normal way, that condition is called permissive condition.

Answer to Problem 1P

Correct answer:

Permissive condition: An environmental condition that allows conditional lethal to live

Explanation of Solution

A condition which allows a mutant allele to behave normally and a conditional lethal mutant grow normally, is known as a permissive condition.

Summary Introduction

e.

To determine:

The phrase that describes “reduced penetrance” among the options given below.

1. one gene affecting more than one phenotype

2. part of a gene that does not contain protein coding information

3. both parental phenotypes are expressed in the F hybrids

4. a heritable change in a gene

5. genes whose alleles alter phenotypes produced by the action of other genes

6. less than 100% of the individuals possessing a particular genotype express it in their phenotype

7. environmental condition that allows conditional lethals to live

8. a trait produced by the interaction of alleles of at least two genes or from interactions between gene and environment

9. individuals with the same genotype have related phenotypes that vary in intensity

10. a genotype that is lethal in some situations (for example, high temperature) but viable in others

11. the heterozygote resembles neither homozygote

Introduction:

Reduced penetrance is that condition when less than 100% of organisms having a specific genotype express it in the phenotype.

Answer to Problem 1P

Correct answer:

Reduced penetrance: Less than 100% of the individuals possessing a particular genotype to express it in their phenotype

Explanation of Solution

The proportion of the organism in a population that carries the alleles for causing disease is referred to as penetrance. Penetrance is categorized into complete and incomplete penetrance. The condition in which a specific genotype that expressed into its phenotype is possessed by a lesser amount of people is known as reduced penetrance.

Summary Introduction

f.

To determine:

The phrase that describes “multifactorial trait” among the options given below.

1. one gene affecting more than one phenotype

2. part of a gene that does not contain protein coding information

3. both parental phenotypes are expressed in the F hybrids

4. a heritable change in a gene

5. genes whose alleles alter phenotypes produced by the action of other genes

6. less than 100% of the individuals possessing a particular genotype express it in their phenotype

7. environmental condition that allows conditional lethals to live

8. a trait produced by the interaction of alleles of at least two genes or from interactions between gene and environment

9. individuals with the same genotype have related phenotypes that vary in intensity

10. a genotype that is lethal in some situations (for example, high temperature) but viable in others

11. the heterozygote resembles neither homozygote

Introduction:

Some of the traits are the result of intercationbetwee certain alleles. Traits developed from such interactions are referred to as multifactorial trait.

Answer to Problem 1P

Correct answer:

Multifactorial trait: A trait produced by the interaction of alleles of at least two genes or from interactions between gene and environment

Explanation of Solution

Multifactorial trait referred to a trait that is expressed by a group of gene or alleles. The interaction of gene and environment results in the expression of a new trait that is known as a multifactorial trait.

Summary Introduction

g.

To determine:

The phrase that describes “incomplete dominance” among the options given below.

1. one gene affecting more than one phenotype

2. part of a gene that does not contain protein-coding information

3. both parental phenotypes are expressed in the F hybrids

4. a heritable change in a gene

5. genes whose alleles alter phenotypes produced by the action of other genes

6. less than 100% of the individuals possessing a particular genotype express it in their phenotype

7. environmental condition that allows conditional lethals to live

8. a trait produced by the interaction of alleles of at least two genes or from interactions between gene and environment

9. individuals with the same genotype have related phenotypes that vary in intensity

10. a genotype that is lethal in some situations (for example, high temperature) but viable in others

11. the heterozygote resembles neither homozygote

Introduction:

When a mixed combination of alleles is produced in the filial generation, the process is referred to as incomplete dominance.

Answer to Problem 1P

Correct answer:

Incomplete dominance: The heterozygote resembles neither homozygote

Explanation of Solution

A condition in which dominant allele do not mask the effect of recessive allele and leads to intermediate inheritance is known as incomplete dominance. For example, pink flowers in snapdragon are formed due to incomplete dominance.

Summary Introduction

h.

To determine:

The phrase that describes “codominance” among the options given below.

1. one gene affecting more than one phenotype

2. part of a gene that does not contain protein coding information

3. both parental phenotypes are expressed in the F hybrids

4. a heritable change in a gene

5. genes whose alleles alter phenotypes produced by the action of other genes

6. less than 100% of the individuals possessing a particular genotype express it in their phenotype

7. environmental condition that allows conditional lethals to live

8. a trait produced by the interaction of alleles of at least two genes or from interactions between gene and environment

9. individuals with the same genotype have related phenotypes that vary in intensity

10. a genotype that is lethal in some situations (for example, high temperature) but viable in others

11. the heterozygote resembles neither homozygote

Introduction:

Codominance is a situation when both the alleles of a particular trait express equally.

Answer to Problem 1P

Correct answer:

Codominance: Both parental phenotypes are expressed in the F₁ hybrids

Explanation of Solution

Codominance is a condition in which the expression of two alleles takes place equally. Neither of the alleles is dominant or recessive, so F₁ hybrids are expressed with both parental phenotypes.

Summary Introduction

i.

To determine:

The phrase that describes “mutation” among the options given below.

1. one gene affecting more than one phenotype

2. part of a gene that does not contain protein coding information

3. both parental phenotypes are expressed in the F hybrids

4. a heritable change in a gene

5. genes whose alleles alter phenotypes produced by the action of other genes

6. less than 100% of the individuals possessing a particular genotype express it in their phenotype

7. environmental condition that allows conditional lethals to live

8. a trait produced by the interaction of alleles of at least two genes or from interactions between gene and environment

9. individuals with the same genotype have related phenotypes that vary in intensity

10. a genotype that is lethal in some situations (for example, high temperature) but viable in others

11. the heterozygote resembles neither homozygote

Introduction:

A sudden and heritable change in the genome of an organism is called mutation.

Answer to Problem 1P

Correct answer:

Mutation: A heritable change in a gene

Explanation of Solution

The mutation is a change in the DNA sequence that alters the genetic information expressed by a gene. The substances which bring mutation are known as mutagens. The mutation in genes can cause many diseases, but some mutation does not result in diseases hence called silent mutations.

Summary Introduction

j.

To determine:

The phrase that describes “pleiotropy” among the options given below.

1. one gene affecting more than one phenotype

2. part of a gene that does not contain protein coding information

3. both parental phenotypes are expressed in the F hybrids

4. a heritable change in a gene

5. genes whose alleles alter phenotypes produced by the action of other genes

6. less than 100% of the individuals possessing a particular genotype express it in their phenotype

7. environmental condition that allows conditional lethals to live

8. a trait produced by the interaction of alleles of at least two genes or from interactions between gene and environment

9. individuals with the same genotype have related phenotypes that vary in intensity

10. a genotype that is lethal in some situations (for example, high temperature) but viable in others

11. the heterozygote resembles neither homozygote

Introduction:

When the expression of one gene is able to control different phenotypes, the process is called pleiotropy.

Answer to Problem 1P

Correct answer:

Pleiotropy: One gene affecting more than one phenotype

Explanation of Solution

Pleiotropy is a condition in which many different traits are controlled by the expression of a single gene. In this mechanism, the same product formed by a single gene is used by a different type of cells.

Summary Introduction

k.

To determine:

The phrase that describes “variable expressivity” among the options given below.

1. one gene affecting more than one phenotype

2. part of a gene that does not contain protein coding information

3. both parental phenotypes are expressed in the F hybrids

4. a heritable change in a gene

5. genes whose alleles alter phenotypes produced by the action of other genes

6. less than 100% of the individuals possessing a particular genotype express it in their phenotype

7. environmental condition that allows conditional lethals to live

8. a trait produced by the interaction of alleles of at least two genes or from interactions between gene and environment

9. individuals with the same genotype have related phenotypes that vary in intensity

10. a genotype that is lethal in some situations (for example, high temperature) but viable in others

11. the heterozygote resembles neither homozygote

Introduction:

Variable expressivity is the variable intensity of phenotypes among the same population.

Answer to Problem 1P

Correct answer:

Variable expressivity: Individuals with the same genotype have related phenotypes that vary in intensity

Explanation of Solution

The extent or severity of the trait expressed by the expression of genotype among individuals of the same population is known as variable expressivity. For example, the intensity of symptoms of a disease may vary among individuals even though they possess the same genotype.