MENDELIAN GENETICS STUDY GUIDE EXAM
Laws of Inheritance, Punnett Squares, and
Traits 2026/2027 Edition
1. Which of the following best defines the term "allele"?
• A) The physical appearance of an organism
• B) The genetic makeup of an organism
• C) The different forms of a gene
• D) The location of a gene on a chromosome
Rationale: Alleles are the different versions of a gene that exist at the same
locus on homologous chromosomes. For example, Y and y are different alleles
of the gene that determines seed color.
2. What is the relationship between alleles and loci?
• A) Alleles are found on different loci on different chromosomes
• B) Alleles occupy the same locus on homologous chromosomes
• C) Alleles can be found at any locus on any chromosome
• D) Alleles and loci are not related concepts
Rationale: Alleles of the same gene are found at the same position (locus) on
homologous chromosomes. This is a fundamental concept in Mendelian
genetics.
3. An autosome is defined as:
• A) A chromosome that determines sex
• B) Any chromosome that is NOT a sex chromosome
• C) A chromosome found only in males
, • D) A chromosome found only in females
Rationale: Autosomes are all chromosomes except the sex chromosomes (X
and Y in humans). Humans have 22 pairs of autosomes and 1 pair of sex
chromosomes.
4. Co-dominant alleles are characterized by:
• A) One allele completely masking the expression of another
• B) Both alleles affecting the phenotype in the heterozygote
• C) Neither allele being expressed in the heterozygote
• D) Alleles that are always lethal
Rationale: In codominance, both alleles are expressed in the heterozygote,
resulting in a phenotype that shows traits from both alleles. For example, AB
blood type shows both A and B antigens.
5. Which of the following is TRUE about co-dominant alleles?
• A) The heterozygote shows an intermediate phenotype
• B) The heterozygote shows both phenotypes simultaneously
• C) Only the dominant allele is expressed
• D) Neither allele is expressed in the heterozygote
Rationale: Unlike incomplete dominance where the heterozygote shows an
intermediate phenotype, codominance results in both alleles being fully
expressed. The heterozygote exhibits characteristics of both alleles.
6. Gregor Mendel's work was significant because:
• A) He discovered DNA structure
• B) He established the basic principles of heredity using pea plants
• C) He was the first to observe chromosomes
, • D) He discovered that genes are made of protein
Rationale: Mendel performed systematic experiments with pea plants and
established the fundamental laws of inheritance, including the Law of
Segregation and the Law of Independent Assortment.
7. What did Mendel use for his genetics experiments?
• A) Fruit flies
• B) Pea plants
• C) Mice
• D) Bacteria
Rationale: Mendel chose pea plants (Pisum sativum) because they were easy
to cultivate, had short generation times, and exhibited easily observable,
distinct traits.
8. Mendel's Law of Segregation states that:
• A) Genes on different chromosomes are inherited independently
• B) The two alleles for a trait separate during gamete formation
• C) Dominant alleles mask recessive alleles
• D) Traits are inherited from only one parent
Rationale: The Law of Segregation explains that during meiosis, the two
alleles for each trait separate, so each gamete receives only one allele from
each gene pair.
9. According to Mendel's Law of Independent Assortment:
• A) All traits are inherited together
• B) Alleles for different traits are inherited independently
• C) Only dominant traits are passed to offspring
Laws of Inheritance, Punnett Squares, and
Traits 2026/2027 Edition
1. Which of the following best defines the term "allele"?
• A) The physical appearance of an organism
• B) The genetic makeup of an organism
• C) The different forms of a gene
• D) The location of a gene on a chromosome
Rationale: Alleles are the different versions of a gene that exist at the same
locus on homologous chromosomes. For example, Y and y are different alleles
of the gene that determines seed color.
2. What is the relationship between alleles and loci?
• A) Alleles are found on different loci on different chromosomes
• B) Alleles occupy the same locus on homologous chromosomes
• C) Alleles can be found at any locus on any chromosome
• D) Alleles and loci are not related concepts
Rationale: Alleles of the same gene are found at the same position (locus) on
homologous chromosomes. This is a fundamental concept in Mendelian
genetics.
3. An autosome is defined as:
• A) A chromosome that determines sex
• B) Any chromosome that is NOT a sex chromosome
• C) A chromosome found only in males
, • D) A chromosome found only in females
Rationale: Autosomes are all chromosomes except the sex chromosomes (X
and Y in humans). Humans have 22 pairs of autosomes and 1 pair of sex
chromosomes.
4. Co-dominant alleles are characterized by:
• A) One allele completely masking the expression of another
• B) Both alleles affecting the phenotype in the heterozygote
• C) Neither allele being expressed in the heterozygote
• D) Alleles that are always lethal
Rationale: In codominance, both alleles are expressed in the heterozygote,
resulting in a phenotype that shows traits from both alleles. For example, AB
blood type shows both A and B antigens.
5. Which of the following is TRUE about co-dominant alleles?
• A) The heterozygote shows an intermediate phenotype
• B) The heterozygote shows both phenotypes simultaneously
• C) Only the dominant allele is expressed
• D) Neither allele is expressed in the heterozygote
Rationale: Unlike incomplete dominance where the heterozygote shows an
intermediate phenotype, codominance results in both alleles being fully
expressed. The heterozygote exhibits characteristics of both alleles.
6. Gregor Mendel's work was significant because:
• A) He discovered DNA structure
• B) He established the basic principles of heredity using pea plants
• C) He was the first to observe chromosomes
, • D) He discovered that genes are made of protein
Rationale: Mendel performed systematic experiments with pea plants and
established the fundamental laws of inheritance, including the Law of
Segregation and the Law of Independent Assortment.
7. What did Mendel use for his genetics experiments?
• A) Fruit flies
• B) Pea plants
• C) Mice
• D) Bacteria
Rationale: Mendel chose pea plants (Pisum sativum) because they were easy
to cultivate, had short generation times, and exhibited easily observable,
distinct traits.
8. Mendel's Law of Segregation states that:
• A) Genes on different chromosomes are inherited independently
• B) The two alleles for a trait separate during gamete formation
• C) Dominant alleles mask recessive alleles
• D) Traits are inherited from only one parent
Rationale: The Law of Segregation explains that during meiosis, the two
alleles for each trait separate, so each gamete receives only one allele from
each gene pair.
9. According to Mendel's Law of Independent Assortment:
• A) All traits are inherited together
• B) Alleles for different traits are inherited independently
• C) Only dominant traits are passed to offspring
