Chapter 2, Problem 1P

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

a. phenotype	1. having two identical alleles of a given gene
b. alleles	2. the allele expressed in the phenotype of the heterozygote
c. independent	3. alternate forms of a gene assortment
d. gametes	4. observable characteristic
e. gene	5. a cross between individuals both heterozygous for two genes
f. segregation	6. alleles of one gene separate into gametes randomly with respect to alleles of other genes
g. heterozygous	7. reproductive cells containing only one copy of each gene
h. dominant	8. the allele that does not contribute to the phenotype of the heterozygote
i. F1	9. the cross of an individual of ambiguous genotype with a homozygous recessive individual
j. test cross	10. An individual with two different alleles of a gene
k. genotype	11. the heritable entity that determines a characteristic
l. recessive	12. the alleles an individual has
m. dihybrid cross	13. the separation of the two alleles of a gene into different gametes
n. homozygote	14. offspring of the P generation

Summary Introduction

a.

To determine:

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

1. Having two identical alleles of a given gene

2. The allele expressed in the phenotype of the heterozygote

3. Alternate forms of a gene assortment

4. Observable characteristic

5. A cross between individuals both heterozygous for two genes

6. Alleles of one gene separate into gametes randomly with respect to alleles of other genes

7. Reproductive cells containing only one copy of each gene

8. The allele that does not contribute to the phenotype of the heterozygote

9. The cross of an individual of ambiguous genotype with a homozygous recessive individual

10. An individual with two different alleles of a gene

11. The heritable entity that determines a characteristic

12. The alleles an individual has

13. The separation of the two alleles of a gene into different gametes

14. Offspring of the P generation

Introduction:

Gene is the basic unit of biological information. The way genes transmit physiological, anatomical, and behavioral traits from parents to offspring is termed as heredity.

Answer to Problem 1P

Correct answer:

Phenotype: Observable characteristic

Explanation of Solution

The observable physical properties of an organism such as appearance, development, and behavior are termed as phenotypes. The phenotype of an individual is determined by its genotype.

Summary Introduction

b.

To determine:

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

1. Having two identical alleles of a given gene

2. The allele expressed in the phenotype of the heterozygote

3. Alternate forms of a gene assortment

4. Observable characteristic

5. A cross between individuals both heterozygous for two genes

6. Alleles of one gene separate into gametes randomly with respect to alleles of other genes

7. Reproductive cells containing only one copy of each gene

8. The allele that does not contribute to the phenotype of the heterozygote

9. The cross of an individual of ambiguous genotype with a homozygous recessive individual

10. An individual with two different alleles of a gene

11. The heritable entity that determines a characteristic

12. The alleles an individual has

13. The separation of the two alleles of a gene into different gametes

14. Offspring of the P generation

Introduction:

Genetics is the science of heredity in which a precise explanation of the biological structures and mechanisms that determine inheritance are studied.

Answer to Problem 1P

Correct answer:

Alleles: alternate forms of a gene assortment

Explanation of Solution

A variant form of a gene is termed as an allele. The genes have a variety of different forms, which are located at the same position, or genetic locus, on a chromosome.

Summary Introduction

c.

To determine:

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

1. Having two identical alleles of a given gene

2. The allele expressed in the phenotype of the heterozygote

3. Alternate forms of a gene assortment

4. Observable characteristic

5. A cross between individuals both heterozygous for two genes

6. Alleles of one gene separate into gametes randomly with respect to alleles of other genes

7. Reproductive cells containing only one copy of each gene

8. The allele that does not contribute to the phenotype of the heterozygote

9. The cross of an individual of ambiguous genotype with a homozygous recessive individual

10. An individual with two different alleles of a gene

11. The heritable entity that determines a characteristic

12. The alleles an individual has

13. The separation of the two alleles of a gene into different gametes

14. Offspring of the P generation

Introduction:

Gregor Mendel was the scientist who explained the fundamental laws of inheritance. His studies on pea plants exposed that genes come in pairs and are inherited as distinct units, one from each parent.

Answer to Problem 1P

Correct answer:

Independent: Alleles of one gene separate into gametes randomly with respect to alleles of other genes

Explanation of Solution

Gregor Mendel stated that the alleles for separate traits are passed to the next generation independent of each other. The selection of one allele is independent of the selection of the other trait.

Summary Introduction

d.

To determine:

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

1. Having two identical alleles of a given gene

2. The allele expressed in the phenotype of the heterozygote

3. Alternate forms of a gene assortment

4. Observable characteristic

5. A cross between individuals both heterozygous for two genes

6. Alleles of one gene separate into gametes randomly with respect to alleles of other genes

7. Reproductive cells containing only one copy of each gene

8. The allele that does not contribute to the phenotype of the heterozygote

9. The cross of an individual of ambiguous genotype with a homozygous recessive individual

10. An individual with two different alleles of a gene

11. The heritable entity that determines a characteristic

12. The alleles an individual has

13. The separation of the two alleles of a gene into different gametes

14. Offspring of the P generation

Introduction:

Gametes are known as sex cells which is produced through the process of meiosis.

Answer to Problem 1P

Correct answer:

Gametes: Reproductive cells containing only one copy of each gene

Explanation of Solution

Gametes are the reproductive cells of an individual. A gamete is a haploid cell that fuses with another haploid cell during fertilization in an individual during sexual reproduction. The two gametes usually look different from each other.

Summary Introduction

e.

To determine:

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

1. Having two identical alleles of a given gene

2. The allele expressed in the phenotype of the heterozygote

3. Alternate forms of a gene assortment

4. Observable characteristic

5. A cross between individuals both heterozygous for two genes

6. Alleles of one gene separate into gametes randomly with respect to alleles of other genes

7. Reproductive cells containing only one copy of each gene

8. The allele that does not contribute to the phenotype of the heterozygote

9. The cross of an individual of ambiguous genotype with a homozygous recessive individual

10. An individual with two different alleles of a gene

11. The heritable entity that determines a characteristic

12. The alleles an individual has

13. The separation of the two alleles of a gene into different gametes

14. Offspring of the P generation

Introduction:

Gene is the basic unit of hereditary information. They are present in the fixed position on a chromosome.

Answer to Problem 1P

Correct answer:

Gene: the heritable entity that determines a characteristic

Explanation of Solution

Gene is termed as a single functional sequence of a DNA or RNA. The different traits of an organism are coded by different functional genes.

Summary Introduction

f.

To determine:

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

1. Having two identical alleles of a given gene

2. The allele expressed in the phenotype of the heterozygote

3. Alternate forms of a gene assortment

4. Observable characteristic

5. A cross between individuals both heterozygous for two genes

6. Alleles of one gene separate into gametes randomly with respect to alleles of other genes

7. Reproductive cells containing only one copy of each gene

8. The allele that does not contribute to the phenotype of the heterozygote

9. The cross of an individual of ambiguous genotype with a homozygous recessive individual

10. An individual with two different alleles of a gene

11. The heritable entity that determines a characteristic

12. The alleles an individual has

13. The separation of the two alleles of a gene into different gametes

14. Offspring of the P generation

Introduction:

Gregor Mendel is the father of genetics and he explained the fundamental laws of inheritance. His studies on pea plants exposed that genes come in pairs and are inherited as distinct units, one from each parent.

Answer to Problem 1P

Correct answer:

Segregation: the separation of the two alleles of a gene into different gametes

Explanation of Solution

According to Gregor Mendel’s law of segregation, the two alleles corresponding to a trait separate from each other during meiosis and segregate into the different gametes.

Summary Introduction

g.

To determine:

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

1. Having two identical alleles of a given gene

2. The allele expressed in the phenotype of the heterozygote

3. Alternate forms of a gene assortment

4. Observable characteristic

5. A cross between individuals both heterozygous for two genes

6. Alleles of one gene separate into gametes randomly with respect to alleles of other genes

7. Reproductive cells containing only one copy of each gene

8. The allele that does not contribute to the phenotype of the heterozygote

9. The cross of an individual of ambiguous genotype with a homozygous recessive individual

10. An individual with two different alleles of a gene

11. The heritable entity that determines a characteristic

12. The alleles an individual has

13. The separation of the two alleles of a gene into different gametes

14. Offspring of the P generation

Introduction:

Genes come in pairs and each pair is present in a specific position or locus on a chromosome. If the locus has two identical alleles, they are homozygous; if the locus has two different alleles, they are heterozygous.

Answer to Problem 1P

Correct answer:

Heterozygous: An individual with two different alleles of a gene

Explanation of Solution

An individual carrying two different alleles of a single gene is termed as a heterozygote. In case of heterozygote, one allele is dominant, and the other gene is recessive.

Summary Introduction

h.

To determine:

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

1. Having two identical alleles of a given gene

2. The allele expressed in the phenotype of the heterozygote

3. Alternate forms of a gene assortment

4. Observable characteristic

5. A cross between individuals both heterozygous for two genes

6. Alleles of one gene separate into gametes randomly with respect to alleles of other genes

7. Reproductive cells containing only one copy of each gene

8. The allele that does not contribute to the phenotype of the heterozygote

9. The cross of an individual of ambiguous genotype with a homozygous recessive individual

10. An individual with two different alleles of a gene

11. The heritable entity that determines a characteristic

12. The alleles an individual has

13. The separation of the two alleles of a gene into different gametes

14. Offspring of the P generation

Introduction:

Dominant and recessive alleles present in a trait that has two different forms at the gene level.

Answer to Problem 1P

Correct answer:

Dominant: the allele expressed in the phenotype of the heterozygote

Explanation of Solution

In genetics, dominance defines the relationship between alleles of one gene. Dominant allele masks the contribution of the recessive allele in the phenotype of any gene.

Summary Introduction

i.

To determine:

The phrase that describes “F₁” among the options given below.

1. Having two identical alleles of a given gene

2. The allele expressed in the phenotype of the heterozygote

3. Alternate forms of a gene assortment

4. Observable characteristic

5. A cross between individuals both heterozygous for two genes

6. Alleles of one gene separate into gametes randomly with respect to alleles of other genes

7. Reproductive cells containing only one copy of each gene

8. The allele that does not contribute to the phenotype of the heterozygote

9. The cross of an individual of ambiguous genotype with a homozygous recessive individual

10. An individual with two different alleles of a gene

11. The heritable entity that determines a characteristic

12. The alleles an individual has

13. The separation of the two alleles of a gene into different gametes

14. Offspring of the P generation

Introduction:

F₁ is also termed as filial 1 generation.

Answer to Problem 1P

Correct answer:

F₁: offspring of the P generation

Explanation of Solution

F₁ generation comes as an offspring formed due to sexual reproduction between parents. F₁ generation is obtained by the fusion of male and female gametes.

Summary Introduction

j.

To determine:

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

1. Having two identical alleles of a given gene

2. The allele expressed in the phenotype of the heterozygote

3. Alternate forms of a gene assortment

4. Observable characteristic

5. A cross between individuals both heterozygous for two genes

6. Alleles of one gene separate into gametes randomly with respect to alleles of other genes

7. Reproductive cells containing only one copy of each gene

8. The allele that does not contribute to the phenotype of the heterozygote

9. The cross of an individual of ambiguous genotype with a homozygous recessive individual

10. An individual with two different alleles of a gene

11. The heritable entity that determines a characteristic

12. The alleles an individual has

13. The separation of the two alleles of a gene into different gametes

14. Offspring of the P generation

Introduction:

Testcross is a very important method to determine the zygosity of the individual.

Answer to Problem 1P

Correct answer:

Testcross: The cross of an individual of ambiguous genotype with a homozygous recessive individual

Explanation of Solution

Testcross involves the breeding of a recessive individual with an individual having unknown zygosity.

Summary Introduction

k.

To determine:

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

1. Having two identical alleles of a given gene

2. The allele expressed in the phenotype of the heterozygote

3. Alternate forms of a gene assortment

4. Observable characteristic

5. A cross between individuals both heterozygous for two genes

6. Alleles of one gene separate into gametes randomly with respect to alleles of other genes

7. Reproductive cells containing only one copy of each gene

8. The allele that does not contribute to the phenotype of the heterozygote

9. The cross of an individual of ambiguous genotype with a homozygous recessive individual

10. An individual with two different alleles of a gene

11. The heritable entity that determines a characteristic

12. The alleles an individual has

13. The separation of the two alleles of a gene into different gametes

14. Offspring of the P generation

Introduction:

The part of the genetic makeup of an organism is called the genotype. It determines the characteristics of an organism.

Answer to Problem 1P

Correct answer:

Genotype: the alleles an individual has

Explanation of Solution

The pair of alleles responsible for the expression of a particular phenotype is known as the genotype. It can consist of a pair of homologous or heterologous alleles.

Summary Introduction

l.

To determine:

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

1. Having two identical alleles of a given gene

2. The allele expressed in the phenotype of the heterozygote

3. Alternate forms of a gene assortment

4. Observable characteristic

5. A cross between individuals both heterozygous for two genes

6. Alleles of one gene separate into gametes randomly with respect to alleles of other genes

7. Reproductive cells containing only one copy of each gene

8. The allele that does not contribute to the phenotype of the heterozygote

9. The cross of an individual of ambiguous genotype with a homozygous recessive individual

10. An individual with two different alleles of a gene

11. The heritable entity that determines a characteristic

12. The alleles an individual has

13. The separation of the two alleles of a gene into different gametes

14. Offspring of the P generation

Introduction:

Dominant and recessive alleles present in a trait that has two different forms at the gene level.

Answer to Problem 1P

Correct answer:

Recessive: The allele that does not contribute to the phenotype of the heterozygote

Explanation of Solution

A recessive trait is a specific form of a trait that does not express itself in the presence of a dominant allele. This trait expresses itself in a pair of homologous recessive alleles.

Summary Introduction

m.

To determine:

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

1. Having two identical alleles of a given gene

2. The allele expressed in the phenotype of the heterozygote

3. Alternate forms of a gene assortment

4. Observable characteristic

5. A cross between individuals both heterozygous for two genes

6. Alleles of one gene separate into gametes randomly with respect to alleles of other genes

7. Reproductive cells containing only one copy of each gene

8. The allele that does not contribute to the phenotype of the heterozygote

9. The cross of an individual of ambiguous genotype with a homozygous recessive individual

10. An individual with two different alleles of a gene

11. The heritable entity that determines a characteristic

12. The alleles an individual has

13. The separation of the two alleles of a gene into different gametes

14. Offspring of the P generation

Introduction:

The cross between two different lines or genes that vary in two observed traits is termed as dihybrid cross.

Answer to Problem 1P

Correct answer:

Dihybrid cross: A cross between individuals both heterozygous for two genes

Explanation of Solution

Dihybrid cross explains the mating experiment between two individuals that are identically hybrid for two traits.

Summary Introduction

n.

To determine:

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

1. Having two identical alleles of a given gene

2. The allele expressed in the phenotype of the heterozygote

3. Alternate forms of a gene assortment

4. Observable characteristic

5. A cross between individuals both heterozygous for two genes

6. Alleles of one gene separate into gametes randomly with respect to alleles of other genes

7. Reproductive cells containing only one copy of each gene

8. The allele that does not contribute to the phenotype of the heterozygote

9. The cross of an individual of ambiguous genotype with a homozygous recessive individual

10. An individual with two different alleles of a gene

11. The heritable entity that determines a characteristic

12. The alleles an individual has

13. The separation of the two alleles of a gene into different gametes

14. Offspring of the P generation

Introduction:

The degree of similarity between the alleles for a trait in an organism is known as zygosity.

Answer to Problem 1P

Correct answer:

Homozygote: having two identical alleles of a given gene

Explanation of Solution

Homozygote is an individual who has two identical alleles of a particular gene or genes.