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HUMAN GENETICS 13TH EDITION BY RICKI LEWIS EXAM 2026
QUESTIONS LATEST 2026 – 2027 VERSION SOLVED
QUESTIONS & ANSWERS
Human Genetics 13th Edition By Ricki Lewis
250 Multiple Choice Questions with Rationales
10-POINT EXAM COVERAGE SUMMARY
Based on the 13th Edition textbook structure :
Part 1: Introduction – The Information in a Human Genome; Cells; Meiosis,
Development, and Aging
Part 2: Transmission Genetics – Single-Gene Inheritance; Beyond Mendel's Laws;
Matters of Sex; Complex Traits; Genetics of Behavior
Part 3: DNA and Chromosomes – DNA Structure and Replication; Gene Action (DNA to
Protein); Gene Expression and Epigenetics; Gene Mutation; Chromosomes; Genomes
Part 4: Population Genetics – Constant Allele Frequencies; Changing Allele
Frequencies; Human Ancestry and Evolution; The Genetics of Identity
Part 5: Immunity and Cancer – Genetics of Immunity; Cancer Genetics and Genomics
Part 6: Genetic Technology – DNA Technologies; Genetic Testing and Treatment;
Reproductive Technologies
SECTION 1: INTRODUCTION AND GENOME ORGANIZATION
(Questions 1-35)
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1. Which of the following best describes the complete genetic material of an
organism, including all of its DNA, which is organized into chromosomes within the
nucleus?
A) Genotype
B) Phenotype
C) Genome
D) Karyotype
Answer: C) Genome
Rationale: The genome represents the entire complement of genetic material in an
organism, encompassing all of its DNA and the genes it contains. A genotype refers
specifically to the alleles present at particular gene loci, while phenotype describes the
observable traits resulting from gene expression. A karyotype is a visual arrangement of
chromosomes used for cytogenetic analysis. The genome is the complete blueprint for
building and maintaining the organism .
2. A human cell in the G1 phase of the cell cycle contains 46 chromosomes. How
many sets of the genome are present in this cell?
A) 1
B) 2
C) 23
D) 46
Answer: B) 2
Rationale: Most human somatic cells contain two sets of the genome, representing one
set inherited from each parent, for a total of 46 chromosomes organized as 23 pairs.
This diploid state ensures that each gene is present in two copies, providing genetic
redundancy and allowing for allelic variation. The haploid number of 23 chromosomes
is found only in gametes (sperm and egg cells), which contain a single set of the
genome .
3. Which of the following represents the correct hierarchical organization of genetic
material, from the smallest structural unit to the largest functional unit?
A) Gene → DNA building block → Chromosome → Genome
B) DNA building block → Gene → Chromosome → Genome
C) Chromosome → Gene → DNA building block → Genome
D) DNA building block → Genome → Gene → Chromosome
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Answer: B) DNA building block → Gene → Chromosome → Genome
Rationale: The hierarchical organization of genetic material begins with the nucleotide,
which is the fundamental building block of DNA. Multiple nucleotides form a gene,
which is a specific sequence that encodes a functional product. Genes are organized
along chromosomes, which are the physical structures that package DNA within the
nucleus. Finally, the genome represents the complete collection of all chromosomes
and genetic material within an organism .
4. Approximately how many DNA base pairs comprise the complete human
genome, representing the total amount of genetic information in each cell?
A) 32,000
B) 320,000
C) 3.2 million
D) 3.2 billion
Answer: D) 3.2 billion
Rationale: The human genome contains approximately 3.2 billion DNA base pairs,
distributed across 23 pairs of chromosomes. This vast amount of genetic information
encodes approximately 20,000-25,000 protein-coding genes, along with regulatory
sequences and non-coding regions that play important roles in genome function and
regulation. This estimate was derived from the Human Genome Project and subsequent
sequencing efforts .
5. What is the primary distinction between a genotype and a phenotype in the
context of human genetics and inheritance?
A) Genotype refers to RNA molecules while phenotype refers to proteins
B) Genotype refers to the alleles present in an individual while phenotype refers to their
expression
C) Genotype refers to environmental influences while phenotype refers to genetic
factors
D) Genotype refers to chromosome number while phenotype refers to gene sequence
Answer: B) Genotype refers to the alleles present in an individual while phenotype
refers to their expression
Rationale: The genotype represents the specific alleles inherited at particular gene loci
within an individual's genome, constituting the genetic instructions. The phenotype
represents the observable characteristics that result from the expression of these
genetic instructions, influenced by both the genotype and environmental factors. The
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relationship between genotype and phenotype is fundamental to understanding
inheritance patterns and how genetic variation leads to diverse traits .
6. What is the specialized field that addresses ethical concerns arising from new
genetic technologies, including genetic testing, treatment options, privacy issues,
and protection against discrimination?
A) Molecular genetics
B) Population genetics
C) Bioethics
D) Epigenetics
Answer: C) Bioethics
Rationale: Bioethics is the field that examines the moral and ethical implications of
biological and medical advances, including genetic technologies. As genetic testing
becomes more accessible and powerful, important questions arise regarding the
appropriate use of genetic information, protection of patient privacy, prevention of
genetic discrimination in employment and insurance, and the ethical boundaries of
genetic modification and reproductive technologies .
7. Humans have 23 pairs of chromosomes in each somatic cell. What is the correct
description of the composition of these 23 pairs?
A) 22 pairs of sex chromosomes and one pair of autosomes
B) 22 pairs of autosomes and one pair of sex chromosomes
C) 23 pairs of autosomes with no sex chromosomes
D) 23 pairs of sex chromosomes with no autosomes
Answer: B) 22 pairs of autosomes and one pair of sex chromosomes
Rationale: Human somatic cells contain 23 pairs of chromosomes, consisting of 22
pairs of autosomes that are the same in both males and females, and one pair of sex
chromosomes that determine biological sex. Females have two X chromosomes (XX),
while males have one X and one Y chromosome (XY). The autosomes carry the vast
majority of protein-coding genes, while the sex chromosomes carry genes that
determine sex and other traits .
8. Genetic variants that occur at a frequency of at least 1% in a population are
referred to as polymorphisms. What is the most common type of polymorphism
found in the human genome?
HUMAN GENETICS 13TH EDITION BY RICKI LEWIS EXAM 2026
QUESTIONS LATEST 2026 – 2027 VERSION SOLVED
QUESTIONS & ANSWERS
Human Genetics 13th Edition By Ricki Lewis
250 Multiple Choice Questions with Rationales
10-POINT EXAM COVERAGE SUMMARY
Based on the 13th Edition textbook structure :
Part 1: Introduction – The Information in a Human Genome; Cells; Meiosis,
Development, and Aging
Part 2: Transmission Genetics – Single-Gene Inheritance; Beyond Mendel's Laws;
Matters of Sex; Complex Traits; Genetics of Behavior
Part 3: DNA and Chromosomes – DNA Structure and Replication; Gene Action (DNA to
Protein); Gene Expression and Epigenetics; Gene Mutation; Chromosomes; Genomes
Part 4: Population Genetics – Constant Allele Frequencies; Changing Allele
Frequencies; Human Ancestry and Evolution; The Genetics of Identity
Part 5: Immunity and Cancer – Genetics of Immunity; Cancer Genetics and Genomics
Part 6: Genetic Technology – DNA Technologies; Genetic Testing and Treatment;
Reproductive Technologies
SECTION 1: INTRODUCTION AND GENOME ORGANIZATION
(Questions 1-35)
, Page 2 of 121
1. Which of the following best describes the complete genetic material of an
organism, including all of its DNA, which is organized into chromosomes within the
nucleus?
A) Genotype
B) Phenotype
C) Genome
D) Karyotype
Answer: C) Genome
Rationale: The genome represents the entire complement of genetic material in an
organism, encompassing all of its DNA and the genes it contains. A genotype refers
specifically to the alleles present at particular gene loci, while phenotype describes the
observable traits resulting from gene expression. A karyotype is a visual arrangement of
chromosomes used for cytogenetic analysis. The genome is the complete blueprint for
building and maintaining the organism .
2. A human cell in the G1 phase of the cell cycle contains 46 chromosomes. How
many sets of the genome are present in this cell?
A) 1
B) 2
C) 23
D) 46
Answer: B) 2
Rationale: Most human somatic cells contain two sets of the genome, representing one
set inherited from each parent, for a total of 46 chromosomes organized as 23 pairs.
This diploid state ensures that each gene is present in two copies, providing genetic
redundancy and allowing for allelic variation. The haploid number of 23 chromosomes
is found only in gametes (sperm and egg cells), which contain a single set of the
genome .
3. Which of the following represents the correct hierarchical organization of genetic
material, from the smallest structural unit to the largest functional unit?
A) Gene → DNA building block → Chromosome → Genome
B) DNA building block → Gene → Chromosome → Genome
C) Chromosome → Gene → DNA building block → Genome
D) DNA building block → Genome → Gene → Chromosome
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Answer: B) DNA building block → Gene → Chromosome → Genome
Rationale: The hierarchical organization of genetic material begins with the nucleotide,
which is the fundamental building block of DNA. Multiple nucleotides form a gene,
which is a specific sequence that encodes a functional product. Genes are organized
along chromosomes, which are the physical structures that package DNA within the
nucleus. Finally, the genome represents the complete collection of all chromosomes
and genetic material within an organism .
4. Approximately how many DNA base pairs comprise the complete human
genome, representing the total amount of genetic information in each cell?
A) 32,000
B) 320,000
C) 3.2 million
D) 3.2 billion
Answer: D) 3.2 billion
Rationale: The human genome contains approximately 3.2 billion DNA base pairs,
distributed across 23 pairs of chromosomes. This vast amount of genetic information
encodes approximately 20,000-25,000 protein-coding genes, along with regulatory
sequences and non-coding regions that play important roles in genome function and
regulation. This estimate was derived from the Human Genome Project and subsequent
sequencing efforts .
5. What is the primary distinction between a genotype and a phenotype in the
context of human genetics and inheritance?
A) Genotype refers to RNA molecules while phenotype refers to proteins
B) Genotype refers to the alleles present in an individual while phenotype refers to their
expression
C) Genotype refers to environmental influences while phenotype refers to genetic
factors
D) Genotype refers to chromosome number while phenotype refers to gene sequence
Answer: B) Genotype refers to the alleles present in an individual while phenotype
refers to their expression
Rationale: The genotype represents the specific alleles inherited at particular gene loci
within an individual's genome, constituting the genetic instructions. The phenotype
represents the observable characteristics that result from the expression of these
genetic instructions, influenced by both the genotype and environmental factors. The
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relationship between genotype and phenotype is fundamental to understanding
inheritance patterns and how genetic variation leads to diverse traits .
6. What is the specialized field that addresses ethical concerns arising from new
genetic technologies, including genetic testing, treatment options, privacy issues,
and protection against discrimination?
A) Molecular genetics
B) Population genetics
C) Bioethics
D) Epigenetics
Answer: C) Bioethics
Rationale: Bioethics is the field that examines the moral and ethical implications of
biological and medical advances, including genetic technologies. As genetic testing
becomes more accessible and powerful, important questions arise regarding the
appropriate use of genetic information, protection of patient privacy, prevention of
genetic discrimination in employment and insurance, and the ethical boundaries of
genetic modification and reproductive technologies .
7. Humans have 23 pairs of chromosomes in each somatic cell. What is the correct
description of the composition of these 23 pairs?
A) 22 pairs of sex chromosomes and one pair of autosomes
B) 22 pairs of autosomes and one pair of sex chromosomes
C) 23 pairs of autosomes with no sex chromosomes
D) 23 pairs of sex chromosomes with no autosomes
Answer: B) 22 pairs of autosomes and one pair of sex chromosomes
Rationale: Human somatic cells contain 23 pairs of chromosomes, consisting of 22
pairs of autosomes that are the same in both males and females, and one pair of sex
chromosomes that determine biological sex. Females have two X chromosomes (XX),
while males have one X and one Y chromosome (XY). The autosomes carry the vast
majority of protein-coding genes, while the sex chromosomes carry genes that
determine sex and other traits .
8. Genetic variants that occur at a frequency of at least 1% in a population are
referred to as polymorphisms. What is the most common type of polymorphism
found in the human genome?
