Mendelian Genetics and Heredity - Numerical Applications
Q. If a plant with genotype AaBb is crossed with another AaBb plant, what fraction of the offspring will be homozygous recessive for both traits?
A.1/16
B.1/4
C.3/16
D.9/16
Solution
The fraction of offspring that are homozygous recessive (aabb) from the cross AaBb x AaBb is 1/16.
Correct Answer: A — 1/16
Q. If a trait is controlled by a single gene with two alleles, what is the maximum number of different genotypes possible in a population?
A.1
B.2
C.3
D.4
Solution
For a single gene with two alleles, the maximum number of different genotypes possible is 3: homozygous dominant, heterozygous, and homozygous recessive.
Correct Answer: D — 4
Q. In a cross between two pea plants, one with round seeds (R) and one with wrinkled seeds (r), what is the phenotype of the F1 generation if round is dominant?
A.Round
B.Wrinkled
C.Both
D.Neither
Solution
The phenotype of the F1 generation will be round seeds since round (R) is dominant over wrinkled (r).
Correct Answer: A — Round
Q. In a test cross, an individual with an unknown genotype is crossed with a homozygous recessive individual. What is the purpose of this cross?
A.To determine the dominant allele
B.To determine the recessive allele
C.To determine the genotype of the unknown
D.To determine the phenotype of the offspring
Solution
The purpose of a test cross is to determine the genotype of an individual with a dominant phenotype by crossing it with a homozygous recessive individual.
Correct Answer: C — To determine the genotype of the unknown
Q. What is the expected phenotypic ratio in the offspring of a monohybrid cross?
A.1:1
B.3:1
C.9:3:3:1
D.1:2:1
Solution
In a monohybrid cross, the expected phenotypic ratio is 3:1, where three offspring display the dominant trait and one displays the recessive trait.
Correct Answer: B — 3:1
Q. What is the probability of obtaining a heterozygous offspring from a cross between two heterozygous parents (Aa x Aa)?
A.0
B.1/4
C.1/2
D.3/4
Solution
The probability of obtaining a heterozygous offspring (Aa) from a cross of Aa x Aa is 1/2.
Correct Answer: C — 1/2
Q. What is the term for an observable characteristic that is influenced by both genetic and environmental factors?
A.Genotype
B.Phenotype
C.Allele
D.Locus
Solution
The term for an observable characteristic influenced by both genetic and environmental factors is phenotype.
Correct Answer: B — Phenotype
Q. What type of mutation involves a change in a single nucleotide base pair?
A.Frameshift mutation
B.Point mutation
C.Deletion mutation
D.Insertion mutation
Solution
A point mutation involves a change in a single nucleotide base pair, which can affect protein synthesis.
