BIOD 210 Genetics Modules 1-7 Bundle
Exam 2026/2027 Comprehensive Test
with Detailed Rationales
1. Which of the following best defines "genetics"?
• A) The study of evolution and natural selection
• B) The study of heredity and the variation of inherited characteristics
• C) The study of cellular metabolism
• D) The study of ecological interactions
Rationale: Genetics is the scientific study of heredity and the variation of inherited
characteristics. It encompasses the transmission of traits from parents to offspring
and the molecular mechanisms underlying these processes.
2. In pea plants, tall (T) is dominant to dwarf (t). Cross a heterozygous tall
plant with a dwarf plant. What is the expected genotypic ratio of offspring?
• A) 1 TT : 1 Tt
• B) 1 Tt : 1 tt
• C) 3 Tt : 1 tt
• D) 1 TT : 2 Tt : 1 tt
Rationale: Tt × tt produces offspring with genotypes 1/2 Tt (tall) and 1/2 tt
(dwarf). The genotypic ratio is 1 Tt : 1 tt.
3. If two heterozygous tall plants (Tt × Tt) are crossed, what fraction of the
tall offspring are expected to be heterozygous?
• A) 1/3
• B) 1/2
• C) 2/3
, • D) 3/4
Rationale: Tt × Tt produces 1 TT : 2 Tt : 1 tt. Tall offspring consist of TT and Tt
(3 total). Among tall offspring, 2/3 are Tt (heterozygous).
4. A man with type AB blood marries a woman with type O blood. What is the
probability their child will have type A blood?
• A) 0%
• B) 25%
• C) 50%
• D) 100%
Rationale: AB (I^A I^B) × O (ii) produces 50% I^A i (type A) and 50% I^B i
(type B). There is a 50% chance the child will have type A blood.
5. The principle of segregation states that:
• A) Alleles of different genes assort independently
• B) Alleles of a gene separate during gamete formation
• C) Dominant alleles mask recessive alleles
• D) Traits are inherited via chromosomes
Rationale: Mendel's first law (the Law of Segregation) states that the two alleles
for a trait separate during gamete formation, so each gamete receives only one
allele from each pair.
6. A test cross is used to determine:
• A) The dominant allele
• B) The genotype of an individual with a dominant phenotype
• C) The number of chromosomes
• D) The sex of an organism
,Rationale: A test cross involves crossing an individual with a dominant phenotype
(unknown genotype) with a homozygous recessive individual. The offspring ratios
reveal whether the dominant individual is homozygous or heterozygous.
7. In guinea pigs, black coat (B) is dominant to white (b). A black guinea pig of
unknown genotype is crossed with a white guinea pig. Half the offspring are
white. What is the black parent's genotype?
• A) BB
• B) Bb
• C) bb
• D) Cannot be determined
Rationale: If the black parent were BB, all offspring would be black (Bb). Since
half the offspring are white (bb), the black parent must be heterozygous (Bb),
producing 1/2 Bb (black) and 1/2 bb (white).
8. In a dihybrid cross (RrYy × RrYy), what fraction of offspring show both
dominant traits (round and yellow)?
• A) 9/16
• B) 3/16
• C) 1/16
• D) 6/16
Rationale: The probability of round (R_) is 3/4 and yellow (Y_) is 3/4. Using the
product rule: 3/4 × 3/4 = 9/16.
9. What is the probability of rolling a 6 on a fair die three times in a row?
• A) 1/6
• B) 1/36
• C) 1/216
, • D) 1/18
Rationale: The probability of rolling a 6 on one die is 1/6. For three independent
events, multiply the probabilities: (1/6) × (1/6) × (1/6) = 1/216.
10. The chromosomal theory of inheritance states that:
• A) Genes are located on chromosomes
• B) Chromosomes are made of DNA
• C) Traits are inherited through cytoplasmic organelles
• D) Only dominant traits are linked to chromosomes
Rationale: Sutton and Boveri proposed that genes are carried on chromosomes,
which explains Mendelian segregation patterns.
11. In humans, the sex chromosomes of a normal male are:
• A) XX
• B) XY
• C) XO
• D) XXY
Rationale: Human males are heterogametic with XY sex chromosomes; females
are homogametic with XX chromosomes.
12. Which of the following is an example of incomplete dominance?
• A) ABO blood types
• B) Pink flowers from a cross between red and white flowers
• C) Pea plant height
• D) Human eye color
Rationale: In incomplete dominance, the heterozygote displays an intermediate
phenotype. Pink flowers from red × white crosses demonstrate this pattern.
Exam 2026/2027 Comprehensive Test
with Detailed Rationales
1. Which of the following best defines "genetics"?
• A) The study of evolution and natural selection
• B) The study of heredity and the variation of inherited characteristics
• C) The study of cellular metabolism
• D) The study of ecological interactions
Rationale: Genetics is the scientific study of heredity and the variation of inherited
characteristics. It encompasses the transmission of traits from parents to offspring
and the molecular mechanisms underlying these processes.
2. In pea plants, tall (T) is dominant to dwarf (t). Cross a heterozygous tall
plant with a dwarf plant. What is the expected genotypic ratio of offspring?
• A) 1 TT : 1 Tt
• B) 1 Tt : 1 tt
• C) 3 Tt : 1 tt
• D) 1 TT : 2 Tt : 1 tt
Rationale: Tt × tt produces offspring with genotypes 1/2 Tt (tall) and 1/2 tt
(dwarf). The genotypic ratio is 1 Tt : 1 tt.
3. If two heterozygous tall plants (Tt × Tt) are crossed, what fraction of the
tall offspring are expected to be heterozygous?
• A) 1/3
• B) 1/2
• C) 2/3
, • D) 3/4
Rationale: Tt × Tt produces 1 TT : 2 Tt : 1 tt. Tall offspring consist of TT and Tt
(3 total). Among tall offspring, 2/3 are Tt (heterozygous).
4. A man with type AB blood marries a woman with type O blood. What is the
probability their child will have type A blood?
• A) 0%
• B) 25%
• C) 50%
• D) 100%
Rationale: AB (I^A I^B) × O (ii) produces 50% I^A i (type A) and 50% I^B i
(type B). There is a 50% chance the child will have type A blood.
5. The principle of segregation states that:
• A) Alleles of different genes assort independently
• B) Alleles of a gene separate during gamete formation
• C) Dominant alleles mask recessive alleles
• D) Traits are inherited via chromosomes
Rationale: Mendel's first law (the Law of Segregation) states that the two alleles
for a trait separate during gamete formation, so each gamete receives only one
allele from each pair.
6. A test cross is used to determine:
• A) The dominant allele
• B) The genotype of an individual with a dominant phenotype
• C) The number of chromosomes
• D) The sex of an organism
,Rationale: A test cross involves crossing an individual with a dominant phenotype
(unknown genotype) with a homozygous recessive individual. The offspring ratios
reveal whether the dominant individual is homozygous or heterozygous.
7. In guinea pigs, black coat (B) is dominant to white (b). A black guinea pig of
unknown genotype is crossed with a white guinea pig. Half the offspring are
white. What is the black parent's genotype?
• A) BB
• B) Bb
• C) bb
• D) Cannot be determined
Rationale: If the black parent were BB, all offspring would be black (Bb). Since
half the offspring are white (bb), the black parent must be heterozygous (Bb),
producing 1/2 Bb (black) and 1/2 bb (white).
8. In a dihybrid cross (RrYy × RrYy), what fraction of offspring show both
dominant traits (round and yellow)?
• A) 9/16
• B) 3/16
• C) 1/16
• D) 6/16
Rationale: The probability of round (R_) is 3/4 and yellow (Y_) is 3/4. Using the
product rule: 3/4 × 3/4 = 9/16.
9. What is the probability of rolling a 6 on a fair die three times in a row?
• A) 1/6
• B) 1/36
• C) 1/216
, • D) 1/18
Rationale: The probability of rolling a 6 on one die is 1/6. For three independent
events, multiply the probabilities: (1/6) × (1/6) × (1/6) = 1/216.
10. The chromosomal theory of inheritance states that:
• A) Genes are located on chromosomes
• B) Chromosomes are made of DNA
• C) Traits are inherited through cytoplasmic organelles
• D) Only dominant traits are linked to chromosomes
Rationale: Sutton and Boveri proposed that genes are carried on chromosomes,
which explains Mendelian segregation patterns.
11. In humans, the sex chromosomes of a normal male are:
• A) XX
• B) XY
• C) XO
• D) XXY
Rationale: Human males are heterogametic with XY sex chromosomes; females
are homogametic with XX chromosomes.
12. Which of the following is an example of incomplete dominance?
• A) ABO blood types
• B) Pink flowers from a cross between red and white flowers
• C) Pea plant height
• D) Human eye color
Rationale: In incomplete dominance, the heterozygote displays an intermediate
phenotype. Pink flowers from red × white crosses demonstrate this pattern.
