Genetics – Comprehensive Study Guide &
Practice Exam
EXAM OVERVIEW
Genetics is the scientific study of heredity and variation in living organisms.
It encompasses the molecular structure and function of genes, gene
expression, patterns of inheritance, genetic disorders, population genetics,
and the role of genes in health and disease.
Key Areas of Study
• Mendelian Genetics: Patterns of inheritance, laws of segregation
and independent assortment
• Molecular Genetics: DNA structure, replication, transcription,
translation, gene regulation
• Cytogenetics: Chromosome structure, karyotyping, chromosomal
abnormalities
• Population Genetics: Gene frequencies, Hardy-Weinberg
equilibrium, evolution
• Medical Genetics: Genetic disorders, carrier screening, genetic
counseling, gene therapy
• Epigenetics: Gene expression without DNA sequence changes
SECTION 1: Mendelian Genetics & Inheritance Patterns
Q1. A heterozygous individual has:
• A) Two identical alleles for a gene
• B) Two different alleles for a gene
• C) Only one allele for a gene
• D) No alleles for a gene
,Answer: B – A heterozygous individual carries two different alleles for a
given gene (e.g., Aa). Homozygous individuals carry two identical alleles (AA
or aa).
Q2. In a monohybrid cross between two heterozygous (Aa × Aa)
individuals, what is the expected phenotypic ratio?
• A) 1:2:1
• B) 3:1
• C) 9:3:3:1
• D) 1:1
Answer: B – A cross between two heterozygotes (Aa × Aa) yields a 3:1
phenotypic ratio (dominant:recessive). The genotypic ratio is 1:2:1
(AA:Aa:aa).
Q3. A dihybrid cross between two heterozygous individuals (AaBb ×
AaBb) yields a phenotypic ratio of:
• A) 3:1
• B) 1:2:1
• C) 9:3:3:1
• D) 9:7
Answer: C – A dihybrid cross between two heterozygotes yields a 9:3:3:1
phenotypic ratio for two independently assorting genes.
Q4. Which of the following is NOT an autosomal dominant disorder?
• A) Huntington's disease
• B) Cystic fibrosis
• C) Marfan syndrome
, • D) Neurofibromatosis type 1
Answer: B – Cystic fibrosis is an autosomal recessive disorder.
Huntington's disease, Marfan syndrome, and neurofibromatosis type 1 are
autosomal dominant disorders.
Q5. An autosomal recessive disorder requires that an individual
inherits:
• A) One affected allele
• B) Two affected alleles (one from each parent)
• C) One affected allele from the mother only
• D) One affected allele from the father only
Answer: B – Autosomal recessive disorders require two copies of the
mutant allele (homozygous recessive). Carriers (heterozygous) do not
typically show symptoms.
Q6. Which of the following is an X-linked recessive disorder?
• A) Huntington's disease
• B) Cystic fibrosis
• C) Hemophilia A
• D) Marfan syndrome
Answer: C – Hemophilia A is an X-linked recessive disorder. Males are more
commonly affected because they have only one X chromosome.
Q7. A color-blind father (X^cY) and a carrier mother (X^cX) have a son.
What is the probability that the son will be color-blind?
• A) 0%
• B) 25%
, • C) 50%
• D) 100%
Answer: C – Sons inherit their X chromosome from their mother. The
mother is a carrier (X^cX), so there is a 50% chance she passes the
affected X chromosome to her son.
Q8. The law of segregation states that:
• A) Genes for different traits segregate independently
• B) Alleles separate during gamete formation
• C) Dominant alleles mask recessive alleles
• D) Linked genes are inherited together
Answer: B – Mendel's law of segregation states that during gamete
formation, the two alleles for each gene separate so that each gamete
receives only one allele.
Q9. The law of independent assortment states that:
• A) Alleles for different genes segregate independently
• B) Alleles for the same gene segregate together
• C) Dominant alleles always assort together
• D) Recessive alleles assort together
Answer: A – Mendel's law of independent assortment states that genes for
different traits segregate independently of one another during gamete
formation, provided they are on different chromosomes.
Q10. A testcross is used to determine whether an individual expressing
a dominant phenotype is:
• A) Homozygous recessive
Practice Exam
EXAM OVERVIEW
Genetics is the scientific study of heredity and variation in living organisms.
It encompasses the molecular structure and function of genes, gene
expression, patterns of inheritance, genetic disorders, population genetics,
and the role of genes in health and disease.
Key Areas of Study
• Mendelian Genetics: Patterns of inheritance, laws of segregation
and independent assortment
• Molecular Genetics: DNA structure, replication, transcription,
translation, gene regulation
• Cytogenetics: Chromosome structure, karyotyping, chromosomal
abnormalities
• Population Genetics: Gene frequencies, Hardy-Weinberg
equilibrium, evolution
• Medical Genetics: Genetic disorders, carrier screening, genetic
counseling, gene therapy
• Epigenetics: Gene expression without DNA sequence changes
SECTION 1: Mendelian Genetics & Inheritance Patterns
Q1. A heterozygous individual has:
• A) Two identical alleles for a gene
• B) Two different alleles for a gene
• C) Only one allele for a gene
• D) No alleles for a gene
,Answer: B – A heterozygous individual carries two different alleles for a
given gene (e.g., Aa). Homozygous individuals carry two identical alleles (AA
or aa).
Q2. In a monohybrid cross between two heterozygous (Aa × Aa)
individuals, what is the expected phenotypic ratio?
• A) 1:2:1
• B) 3:1
• C) 9:3:3:1
• D) 1:1
Answer: B – A cross between two heterozygotes (Aa × Aa) yields a 3:1
phenotypic ratio (dominant:recessive). The genotypic ratio is 1:2:1
(AA:Aa:aa).
Q3. A dihybrid cross between two heterozygous individuals (AaBb ×
AaBb) yields a phenotypic ratio of:
• A) 3:1
• B) 1:2:1
• C) 9:3:3:1
• D) 9:7
Answer: C – A dihybrid cross between two heterozygotes yields a 9:3:3:1
phenotypic ratio for two independently assorting genes.
Q4. Which of the following is NOT an autosomal dominant disorder?
• A) Huntington's disease
• B) Cystic fibrosis
• C) Marfan syndrome
, • D) Neurofibromatosis type 1
Answer: B – Cystic fibrosis is an autosomal recessive disorder.
Huntington's disease, Marfan syndrome, and neurofibromatosis type 1 are
autosomal dominant disorders.
Q5. An autosomal recessive disorder requires that an individual
inherits:
• A) One affected allele
• B) Two affected alleles (one from each parent)
• C) One affected allele from the mother only
• D) One affected allele from the father only
Answer: B – Autosomal recessive disorders require two copies of the
mutant allele (homozygous recessive). Carriers (heterozygous) do not
typically show symptoms.
Q6. Which of the following is an X-linked recessive disorder?
• A) Huntington's disease
• B) Cystic fibrosis
• C) Hemophilia A
• D) Marfan syndrome
Answer: C – Hemophilia A is an X-linked recessive disorder. Males are more
commonly affected because they have only one X chromosome.
Q7. A color-blind father (X^cY) and a carrier mother (X^cX) have a son.
What is the probability that the son will be color-blind?
• A) 0%
• B) 25%
, • C) 50%
• D) 100%
Answer: C – Sons inherit their X chromosome from their mother. The
mother is a carrier (X^cX), so there is a 50% chance she passes the
affected X chromosome to her son.
Q8. The law of segregation states that:
• A) Genes for different traits segregate independently
• B) Alleles separate during gamete formation
• C) Dominant alleles mask recessive alleles
• D) Linked genes are inherited together
Answer: B – Mendel's law of segregation states that during gamete
formation, the two alleles for each gene separate so that each gamete
receives only one allele.
Q9. The law of independent assortment states that:
• A) Alleles for different genes segregate independently
• B) Alleles for the same gene segregate together
• C) Dominant alleles always assort together
• D) Recessive alleles assort together
Answer: A – Mendel's law of independent assortment states that genes for
different traits segregate independently of one another during gamete
formation, provided they are on different chromosomes.
Q10. A testcross is used to determine whether an individual expressing
a dominant phenotype is:
• A) Homozygous recessive
