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BIOL180 UNIT TEST 6 – MENDELIAN GENETICS AND
INHERITANCE EXAM PRACTICE 2026/2027 COMPLETE
CURRENT TESTING QUESTIONS AND CORRECT
ANSWERS WITH DETAILED RATIONALES.
BIOL
Prepare for the BIOL180 Unit Test 6 – Mendelian Genetics and Inheritance Exam with
this focused practice resource designed to reinforce essential genetics concepts. Use
it to review Mendelian principles, inheritance patterns, alleles, genotypes,
phenotypes, and genetic crosses. This resource can help strengthen your
understanding, identify areas that may require additional study, and improve your test
readiness. It provides a structured supplement to your coursework and supports a
more confident approach to the BIOL180 assessment.
MULTIPLE CHOICE.
Module 1: Mendel, Terminology & Basic Principles (Questions 1–20)
1. Who is considered the father of genetics?
A. Charles Darwin
B. Gregor Mendel
C. James Watson
D. Francis Crick
Answer: B
Rationale: Gregor Mendel is considered the father of genetics because his
experiments with pea plants established the basic principles of
inheritance.
2. Why did Mendel use pea plants for his experiments?
A. They reproduce slowly
B. They have easily observable traits and can be controlled for breeding
C. They have no genetic variation
D. They only self-pollinate
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Answer: B
Rationale: Pea plants have distinct traits, short generation times, and can
be cross-pollinated or self-pollinated, making them ideal for genetic
studies.
3. A true-breeding organism is one that:
A. Is always heterozygous
B. Produces offspring with the same trait generation after generation
C. Shows only recessive traits
D. Cannot reproduce
Answer: B
Rationale: True-breeding organisms are homozygous for a trait and
produce offspring with the same phenotype when self-fertilized.
4. An allele is best defined as:
A. A type of chromosome
B. An alternative form of a gene
C. A protein produced by a gene
D. A cell organelle
Answer: B
Rationale: An allele is one of two or more alternative forms of a gene that
occupy the same locus on homologous chromosomes.
5. Genotype refers to:
A. The physical appearance of an organism
B. The genetic makeup of an organism
C. The environment of an organism
D. The behavior of an organism
Answer: B
Rationale: Genotype is the genetic makeup of an organism, while
phenotype is the observable physical or physiological trait.
6. Phenotype refers to:
A. The genetic makeup of an organism
B. The observable characteristics of an organism
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C. The alleles inherited from only one parent
D. The number of chromosomes
Answer: B
Rationale: Phenotype is the observable expression of traits, resulting from
genotype and environmental influences.
7. An organism that is homozygous for a gene has:
A. Two identical alleles
B. Two different alleles
C. No alleles
D. Only dominant alleles
Answer: A
Rationale: Homozygous means having two identical alleles for a
particular gene, such as TT or tt.
8. An organism that is heterozygous for a gene has:
A. Two identical alleles
B. Two different alleles
C. No alleles
D. Only recessive alleles
Answer: B
Rationale: Heterozygous means having two different alleles for a
particular gene, such as Tt.
9. A dominant allele is one that:
A. Is masked by the recessive allele
B. Masks the expression of the recessive allele
C. Is always lethal
D. Only appears in males
Answer: B
Rationale: A dominant allele is expressed in the phenotype even when
only one copy is present.
10. A recessive allele is expressed only when:
A. One copy is present
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B. Two copies are present
C. It is on the X chromosome
D. It is on the Y chromosome
Answer: B
Rationale: A recessive allele is expressed only in the homozygous
condition, when two copies are present.
11. Mendel’s law of segregation states that:
A. Genes on different chromosomes assort independently
B. Two alleles for a trait separate during gamete formation
C. All alleles are dominant
D. Traits blend together
Answer: B
Rationale: The law of segregation states that the two alleles for a gene
separate during meiosis, so each gamete receives one allele.
12. Mendel’s law of independent assortment states that:
A. Alleles for different genes on different chromosomes assort independently
B. Alleles for the same gene separate
C. All traits are linked
D. Dominant alleles always assort together
Answer: A
Rationale: Independent assortment states that genes on different
chromosomes are distributed to gametes independently of one another.
13. The P generation in a genetic cross refers to:
A. The parental generation
B. The first filial generation
C. The second filial generation
D. The testcross generation
Answer: A
Rationale: The P generation is the parental generation in a genetic cross.
14. The F1 generation refers to:
A. The parental generation
BIOL180 UNIT TEST 6 – MENDELIAN GENETICS AND
INHERITANCE EXAM PRACTICE 2026/2027 COMPLETE
CURRENT TESTING QUESTIONS AND CORRECT
ANSWERS WITH DETAILED RATIONALES.
BIOL
Prepare for the BIOL180 Unit Test 6 – Mendelian Genetics and Inheritance Exam with
this focused practice resource designed to reinforce essential genetics concepts. Use
it to review Mendelian principles, inheritance patterns, alleles, genotypes,
phenotypes, and genetic crosses. This resource can help strengthen your
understanding, identify areas that may require additional study, and improve your test
readiness. It provides a structured supplement to your coursework and supports a
more confident approach to the BIOL180 assessment.
MULTIPLE CHOICE.
Module 1: Mendel, Terminology & Basic Principles (Questions 1–20)
1. Who is considered the father of genetics?
A. Charles Darwin
B. Gregor Mendel
C. James Watson
D. Francis Crick
Answer: B
Rationale: Gregor Mendel is considered the father of genetics because his
experiments with pea plants established the basic principles of
inheritance.
2. Why did Mendel use pea plants for his experiments?
A. They reproduce slowly
B. They have easily observable traits and can be controlled for breeding
C. They have no genetic variation
D. They only self-pollinate
, Page 2 of 33
Answer: B
Rationale: Pea plants have distinct traits, short generation times, and can
be cross-pollinated or self-pollinated, making them ideal for genetic
studies.
3. A true-breeding organism is one that:
A. Is always heterozygous
B. Produces offspring with the same trait generation after generation
C. Shows only recessive traits
D. Cannot reproduce
Answer: B
Rationale: True-breeding organisms are homozygous for a trait and
produce offspring with the same phenotype when self-fertilized.
4. An allele is best defined as:
A. A type of chromosome
B. An alternative form of a gene
C. A protein produced by a gene
D. A cell organelle
Answer: B
Rationale: An allele is one of two or more alternative forms of a gene that
occupy the same locus on homologous chromosomes.
5. Genotype refers to:
A. The physical appearance of an organism
B. The genetic makeup of an organism
C. The environment of an organism
D. The behavior of an organism
Answer: B
Rationale: Genotype is the genetic makeup of an organism, while
phenotype is the observable physical or physiological trait.
6. Phenotype refers to:
A. The genetic makeup of an organism
B. The observable characteristics of an organism
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C. The alleles inherited from only one parent
D. The number of chromosomes
Answer: B
Rationale: Phenotype is the observable expression of traits, resulting from
genotype and environmental influences.
7. An organism that is homozygous for a gene has:
A. Two identical alleles
B. Two different alleles
C. No alleles
D. Only dominant alleles
Answer: A
Rationale: Homozygous means having two identical alleles for a
particular gene, such as TT or tt.
8. An organism that is heterozygous for a gene has:
A. Two identical alleles
B. Two different alleles
C. No alleles
D. Only recessive alleles
Answer: B
Rationale: Heterozygous means having two different alleles for a
particular gene, such as Tt.
9. A dominant allele is one that:
A. Is masked by the recessive allele
B. Masks the expression of the recessive allele
C. Is always lethal
D. Only appears in males
Answer: B
Rationale: A dominant allele is expressed in the phenotype even when
only one copy is present.
10. A recessive allele is expressed only when:
A. One copy is present
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B. Two copies are present
C. It is on the X chromosome
D. It is on the Y chromosome
Answer: B
Rationale: A recessive allele is expressed only in the homozygous
condition, when two copies are present.
11. Mendel’s law of segregation states that:
A. Genes on different chromosomes assort independently
B. Two alleles for a trait separate during gamete formation
C. All alleles are dominant
D. Traits blend together
Answer: B
Rationale: The law of segregation states that the two alleles for a gene
separate during meiosis, so each gamete receives one allele.
12. Mendel’s law of independent assortment states that:
A. Alleles for different genes on different chromosomes assort independently
B. Alleles for the same gene separate
C. All traits are linked
D. Dominant alleles always assort together
Answer: A
Rationale: Independent assortment states that genes on different
chromosomes are distributed to gametes independently of one another.
13. The P generation in a genetic cross refers to:
A. The parental generation
B. The first filial generation
C. The second filial generation
D. The testcross generation
Answer: A
Rationale: The P generation is the parental generation in a genetic cross.
14. The F1 generation refers to:
A. The parental generation
