BIOL320 EXAM 1 2026 | UPDATED QUESTIONS AND CORRECT
ANSWERS | ALREADY GRADED A+ | VERIFIED ANSWERS | JUST
RELEASED
1. A diploid organism has a gene with two alleles, A and a, and a heterozygous
individual is crossed with another heterozygous individual. Which genotype
ratio would be expected among the offspring if the alleles follow simple
Mendelian inheritance with complete dominance?
A. 1 AA : 2 Aa : 1 aa
B. 3 AA : 1 aa
C. 1 AA : 1 Aa : 2 aa
D. 2 AA : 1 Aa : 1 aa
Answer: A
2. A researcher crosses two organisms that are both heterozygous for a trait
controlled by a single gene with complete dominance. What phenotypic
ratio should be expected among a large number of offspring?
A. 1 dominant : 1 recessive
B. 3 dominant : 1 recessive
C. 1 dominant : 2 recessive
D. 2 dominant : 2 recessive
Answer: B
3. An individual displays a recessive phenotype for a trait caused by a single
autosomal gene with complete dominance. Which genotype must the
individual possess?
A. AA
B. Aa
C. aa
D. A0
Answer: C
4. A plant with genotype Aa is crossed with a plant having genotype aa.
Assuming complete dominance and independent segregation, what
pg. 1
, proportion of offspring is expected to have the recessive phenotype?
A. 25%
B. 50%
C. 75%
D. 100%
Answer: B
5. A geneticist crosses an organism displaying a dominant phenotype with a
homozygous recessive organism to determine whether the unknown parent
is homozygous or heterozygous. What type of cross is being performed?
A. Dihybrid cross
B. Reciprocal cross
C. Testcross
D. Backcross involving two dominant parents
Answer: C
6. Two parents are both heterozygous for an autosomal recessive disorder.
What is the probability that their child will be homozygous recessive?
A. 75%
B. 50%
C. 25%
D. 100%
Answer: C
7. A family has a genetic trait in which affected individuals frequently appear
among siblings even though neither parent expresses the phenotype.
Which inheritance pattern is most consistent with this observation?
A. Autosomal recessive
B. Autosomal dominant
C. Y-linked
D. Mitochondrial only
Answer: A
8. A trait is observed in every generation, affected individuals usually have an
affected parent, and males and females are affected at similar frequencies.
pg. 2
, Which inheritance pattern is most consistent with these observations?
A. Autosomal dominant
B. Autosomal recessive
C. Y-linked recessive
D. Mitochondrial recessive
Answer: A
9. Two genes are located on different chromosomes and assort independently
during meiosis. A parent is heterozygous for both genes. Which principle
explains the independent distribution of the alleles of these genes into
gametes?
A. Law of segregation only
B. Law of independent assortment
C. Principle of genetic linkage
D. Central dogma
Answer: B
10. An individual with genotype AaBb produces gametes under conditions in
which the two genes assort independently. Which set represents the
possible gametes?
A. AA, BB, aa, bb
B. AB, Ab, aB, ab
C. Aa, Bb, AB, ab
D. AABB, AAbb, aaBB, aabb
Answer: B
11. A dihybrid cross is performed between two individuals with genotype AaBb.
Assuming complete dominance and independent assortment, which
phenotypic ratio is expected?
A. 1:1:1:1
B. 9:3:3:1
C. 3:1
D. 1:2:1
Answer: B
pg. 3
, 12. A researcher observes offspring from a dihybrid cross and obtains a ratio
that differs substantially from the expected Mendelian ratio. Which factor
could explain this deviation in a relatively small sample?
A. Sampling error
B. The impossibility of independent assortment
C. DNA containing nucleotides
D. Chromosomes always remaining paired after meiosis
Answer: A
13. A trait shows incomplete dominance, meaning heterozygotes have an
intermediate phenotype between the two homozygotes. If red flowers are
RR, white flowers are rr, and pink flowers are Rr, what phenotype is
expected from crossing two pink plants?
A. All red
B. 3 red : 1 white
C. 1 red : 2 pink : 1 white
D. 1 pink : 1 white
Answer: C
14. In a genetic system exhibiting codominance, a heterozygous individual
expresses both alleles distinctly rather than showing an intermediate
phenotype. Which example best illustrates codominance?
A. A heterozygote with an intermediate color
B. A person expressing both A and B blood-group antigens
C. A recessive phenotype appearing only in homozygotes
D. A trait controlled by mitochondrial DNA
Answer: B
15. A human has blood type AB. Which statement correctly describes the
person’s ABO genotype?
A. The person must be homozygous IAIA
B. The person must be homozygous IBIB
C. The person possesses both IA and IB alleles
pg. 4
ANSWERS | ALREADY GRADED A+ | VERIFIED ANSWERS | JUST
RELEASED
1. A diploid organism has a gene with two alleles, A and a, and a heterozygous
individual is crossed with another heterozygous individual. Which genotype
ratio would be expected among the offspring if the alleles follow simple
Mendelian inheritance with complete dominance?
A. 1 AA : 2 Aa : 1 aa
B. 3 AA : 1 aa
C. 1 AA : 1 Aa : 2 aa
D. 2 AA : 1 Aa : 1 aa
Answer: A
2. A researcher crosses two organisms that are both heterozygous for a trait
controlled by a single gene with complete dominance. What phenotypic
ratio should be expected among a large number of offspring?
A. 1 dominant : 1 recessive
B. 3 dominant : 1 recessive
C. 1 dominant : 2 recessive
D. 2 dominant : 2 recessive
Answer: B
3. An individual displays a recessive phenotype for a trait caused by a single
autosomal gene with complete dominance. Which genotype must the
individual possess?
A. AA
B. Aa
C. aa
D. A0
Answer: C
4. A plant with genotype Aa is crossed with a plant having genotype aa.
Assuming complete dominance and independent segregation, what
pg. 1
, proportion of offspring is expected to have the recessive phenotype?
A. 25%
B. 50%
C. 75%
D. 100%
Answer: B
5. A geneticist crosses an organism displaying a dominant phenotype with a
homozygous recessive organism to determine whether the unknown parent
is homozygous or heterozygous. What type of cross is being performed?
A. Dihybrid cross
B. Reciprocal cross
C. Testcross
D. Backcross involving two dominant parents
Answer: C
6. Two parents are both heterozygous for an autosomal recessive disorder.
What is the probability that their child will be homozygous recessive?
A. 75%
B. 50%
C. 25%
D. 100%
Answer: C
7. A family has a genetic trait in which affected individuals frequently appear
among siblings even though neither parent expresses the phenotype.
Which inheritance pattern is most consistent with this observation?
A. Autosomal recessive
B. Autosomal dominant
C. Y-linked
D. Mitochondrial only
Answer: A
8. A trait is observed in every generation, affected individuals usually have an
affected parent, and males and females are affected at similar frequencies.
pg. 2
, Which inheritance pattern is most consistent with these observations?
A. Autosomal dominant
B. Autosomal recessive
C. Y-linked recessive
D. Mitochondrial recessive
Answer: A
9. Two genes are located on different chromosomes and assort independently
during meiosis. A parent is heterozygous for both genes. Which principle
explains the independent distribution of the alleles of these genes into
gametes?
A. Law of segregation only
B. Law of independent assortment
C. Principle of genetic linkage
D. Central dogma
Answer: B
10. An individual with genotype AaBb produces gametes under conditions in
which the two genes assort independently. Which set represents the
possible gametes?
A. AA, BB, aa, bb
B. AB, Ab, aB, ab
C. Aa, Bb, AB, ab
D. AABB, AAbb, aaBB, aabb
Answer: B
11. A dihybrid cross is performed between two individuals with genotype AaBb.
Assuming complete dominance and independent assortment, which
phenotypic ratio is expected?
A. 1:1:1:1
B. 9:3:3:1
C. 3:1
D. 1:2:1
Answer: B
pg. 3
, 12. A researcher observes offspring from a dihybrid cross and obtains a ratio
that differs substantially from the expected Mendelian ratio. Which factor
could explain this deviation in a relatively small sample?
A. Sampling error
B. The impossibility of independent assortment
C. DNA containing nucleotides
D. Chromosomes always remaining paired after meiosis
Answer: A
13. A trait shows incomplete dominance, meaning heterozygotes have an
intermediate phenotype between the two homozygotes. If red flowers are
RR, white flowers are rr, and pink flowers are Rr, what phenotype is
expected from crossing two pink plants?
A. All red
B. 3 red : 1 white
C. 1 red : 2 pink : 1 white
D. 1 pink : 1 white
Answer: C
14. In a genetic system exhibiting codominance, a heterozygous individual
expresses both alleles distinctly rather than showing an intermediate
phenotype. Which example best illustrates codominance?
A. A heterozygote with an intermediate color
B. A person expressing both A and B blood-group antigens
C. A recessive phenotype appearing only in homozygotes
D. A trait controlled by mitochondrial DNA
Answer: B
15. A human has blood type AB. Which statement correctly describes the
person’s ABO genotype?
A. The person must be homozygous IAIA
B. The person must be homozygous IBIB
C. The person possesses both IA and IB alleles
pg. 4
