Complete Test Bank for
Introduction to Genetic Analysis,
12th Edition by Griffiths – Verified
Questions and Detailed Answers
Covering Chapters 1-20
1 Chapter 1: The Genetics Revolution
1. A sample of normal double-stranded DNA has a guanine content of 18%.
What is the expected proportion of adenine?
a. 9%
b. 32%
c. 36%
d. 68%
e. 82%
Answer: b (Since A pairs with T and G with C, adenine equals thymine, so
100% - 18% G - 18% C = 64%, thus A = 32%.)
2. In one strand of DNA, the nucleotide sequence is 5’-ATGC-3’. The comple-
mentary sequence in the other strand is
a. 3’-ATGC-5’
b. 3’-TACG-5’
c. 5’-ATCG-3’
d. 5’-CGTA-3’
e. 5’-TACG-3’
Answer: b (Complementary bases pair A-T, G-C, and strands are antiparal-
lel.)
3. Which of the following is true about the DNA structure solved by Watson
and Crick?
a. It is a double-helical structure
b. Sugar–phosphate backbone is outside
c. Two hydrogen bonds between A and T, three between C and G
1
, d. Four types of nitrogenous bases
e. All of the above
Answer: e (All describe the DNA double helix.)
4. What is the basic unit of heredity?
a. Chromosome
b. Gene
c. Cell
d. Nucleus
e. Organism
Answer: b (A gene carries hereditary information.)
5. The process by which DNA makes a copy of itself is called
a. Transcription
b. Translation
c. Replication
d. Mutation
e. Recombination
Answer: c (Replication copies DNA for cell division.)
2 Chapter 2: Single-Gene Inheritance
1. If a plant of genotype A/a is selfed, what proportion of the progeny is ex-
pected to have homozygous genotypes?
a. 0
b. 25%
c. 50%
d. 75%
e. 100%
Answer: c (25% AA, 25% aa, total 50% homozygous.)
2. In a monohybrid cross between Aa x Aa, the phenotypic ratio in offspring
is
a. 1:1
b. 3:1
c. 1:2:1
d. 9:3:3:1
2
, e. All dominant
Answer: b (Three dominant to one recessive.)
3. Mendel’s law of segregation states that
a. Genes are on chromosomes
b. Alleles separate during gamete formation
c. Traits blend in offspring
d. Dominant traits always win
e. All traits are inherited together
Answer: b (Each gamete gets one allele.)
4. A test cross involves crossing with
a. Homozygous recessive
b. Homozygous dominant
c. Heterozygote
d. Mutant
e. Wild type
Answer: a (Tests unknown genotype against recessive.)
5. In complete dominance, the heterozygous phenotype
a. Blends with recessive
b. Shows dominant trait
c. Shows recessive trait
d. New trait appears
e. No trait shows
Answer: b (Heterozygote expresses dominant trait.)
3 Chapter 3: Independent Assortment of Genes
1. For two genes, AaBb x AaBb, what is the expected phenotypic ratio?
a. 1:1:1:1
b. 3:1
c. 9:3:3:1
d. 1:2:1
e. All same
Answer: c (Dihybrid cross gives 9:3:3:1 for independent traits.)
3
, 2. What does Mendel’s law of independent assortment state?
a. Genes on different chromosomes assort independently
b. Alleles always stay together
c. Dominant genes link
d. Recessive genes separate
e. Traits are linked by environment
Answer: a (Genes on separate chromosomes assort independently.)
3. How many gamete types can be produced from a dihybrid AaBb?
a. 1
b. 2
c. 4
d. 8
e. 16
Answer: c (22 = 4 gamete types: AB, Ab, aB, ab.)
4. Independent assortment occurs during
a. Mitosis
b. Meiosis
c. Replication
d. Transcription
e. Translation
Answer: b (Meiosis shuffles genes.)
5. A dihybrid cross involves
a. One gene
b. Two genes
c. Three genes
d. Four genes
e. Many genes
Answer: b (Two gene pairs are studied.)
4 Chapter 4: Mapping Eukaryote Chromosomes by
Recombination
1. What is genetic linkage?
4
Introduction to Genetic Analysis,
12th Edition by Griffiths – Verified
Questions and Detailed Answers
Covering Chapters 1-20
1 Chapter 1: The Genetics Revolution
1. A sample of normal double-stranded DNA has a guanine content of 18%.
What is the expected proportion of adenine?
a. 9%
b. 32%
c. 36%
d. 68%
e. 82%
Answer: b (Since A pairs with T and G with C, adenine equals thymine, so
100% - 18% G - 18% C = 64%, thus A = 32%.)
2. In one strand of DNA, the nucleotide sequence is 5’-ATGC-3’. The comple-
mentary sequence in the other strand is
a. 3’-ATGC-5’
b. 3’-TACG-5’
c. 5’-ATCG-3’
d. 5’-CGTA-3’
e. 5’-TACG-3’
Answer: b (Complementary bases pair A-T, G-C, and strands are antiparal-
lel.)
3. Which of the following is true about the DNA structure solved by Watson
and Crick?
a. It is a double-helical structure
b. Sugar–phosphate backbone is outside
c. Two hydrogen bonds between A and T, three between C and G
1
, d. Four types of nitrogenous bases
e. All of the above
Answer: e (All describe the DNA double helix.)
4. What is the basic unit of heredity?
a. Chromosome
b. Gene
c. Cell
d. Nucleus
e. Organism
Answer: b (A gene carries hereditary information.)
5. The process by which DNA makes a copy of itself is called
a. Transcription
b. Translation
c. Replication
d. Mutation
e. Recombination
Answer: c (Replication copies DNA for cell division.)
2 Chapter 2: Single-Gene Inheritance
1. If a plant of genotype A/a is selfed, what proportion of the progeny is ex-
pected to have homozygous genotypes?
a. 0
b. 25%
c. 50%
d. 75%
e. 100%
Answer: c (25% AA, 25% aa, total 50% homozygous.)
2. In a monohybrid cross between Aa x Aa, the phenotypic ratio in offspring
is
a. 1:1
b. 3:1
c. 1:2:1
d. 9:3:3:1
2
, e. All dominant
Answer: b (Three dominant to one recessive.)
3. Mendel’s law of segregation states that
a. Genes are on chromosomes
b. Alleles separate during gamete formation
c. Traits blend in offspring
d. Dominant traits always win
e. All traits are inherited together
Answer: b (Each gamete gets one allele.)
4. A test cross involves crossing with
a. Homozygous recessive
b. Homozygous dominant
c. Heterozygote
d. Mutant
e. Wild type
Answer: a (Tests unknown genotype against recessive.)
5. In complete dominance, the heterozygous phenotype
a. Blends with recessive
b. Shows dominant trait
c. Shows recessive trait
d. New trait appears
e. No trait shows
Answer: b (Heterozygote expresses dominant trait.)
3 Chapter 3: Independent Assortment of Genes
1. For two genes, AaBb x AaBb, what is the expected phenotypic ratio?
a. 1:1:1:1
b. 3:1
c. 9:3:3:1
d. 1:2:1
e. All same
Answer: c (Dihybrid cross gives 9:3:3:1 for independent traits.)
3
, 2. What does Mendel’s law of independent assortment state?
a. Genes on different chromosomes assort independently
b. Alleles always stay together
c. Dominant genes link
d. Recessive genes separate
e. Traits are linked by environment
Answer: a (Genes on separate chromosomes assort independently.)
3. How many gamete types can be produced from a dihybrid AaBb?
a. 1
b. 2
c. 4
d. 8
e. 16
Answer: c (22 = 4 gamete types: AB, Ab, aB, ab.)
4. Independent assortment occurs during
a. Mitosis
b. Meiosis
c. Replication
d. Transcription
e. Translation
Answer: b (Meiosis shuffles genes.)
5. A dihybrid cross involves
a. One gene
b. Two genes
c. Three genes
d. Four genes
e. Many genes
Answer: b (Two gene pairs are studied.)
4 Chapter 4: Mapping Eukaryote Chromosomes by
Recombination
1. What is genetic linkage?
4
