Question 1

In a cross between a homozygous dominant (AA) and a homozygous recessive (aa) organism, what will be the genotype of all F1 offspring?

Accepted Answer

In a monohybrid cross between homozygous dominant (AA) and homozygous recessive (aa), all F1 offspring receive one dominant and one recessive allele, resulting in Aa genotype.

Question 2

Which of the following best describes a recessive trait?

Accepted Answer

A recessive trait is expressed only when an organism is homozygous for the recessive allele (aa), as the recessive allele is masked by the dominant allele in heterozygous conditions.

Question 3

If a heterozygous tall plant (Tt) is crossed with a homozygous short plant (tt), what percentage of the offspring will be tall?

Accepted Answer

In a testcross (Tt × tt), the offspring genotypes are Tt (tall) and tt (short) in a 1:1 ratio, giving 50% tall offspring.

Question 4

What is the term used for different forms of a gene at the same locus on a chromosome?

Accepted Answer

Alleles are alternative forms of a gene that occupy the same position (locus) on homologous chromosomes and code for different versions of the same trait.

Question 5

In a monohybrid cross between a homozygous dominant plant (TT) and a homozygous recessive plant (tt), what is the genotypic ratio of the F1 generation?

Accepted Answer

All F1 offspring from a cross between TT and tt will have the genotype Tt, as each parent contributes one allele.

Question 6

Mendel's law of segregation states that alleles of a gene separate during which process?

Accepted Answer

During meiosis, homologous chromosomes (carrying different alleles) separate, ensuring each gamete receives only one allele of each gene.

Question 7

If a trait shows a phenotypic ratio of 3:1 in the F2 generation of a monohybrid cross, which statement is true about the F1 parents?

Accepted Answer

A 3:1 ratio in F2 results from crossing two heterozygous (Tt × Tt) F1 individuals, which themselves came from a monohybrid cross.

Question 8

A recessive trait appears in the offspring even though neither parent displays the trait. This is an example of which genetic principle?

Accepted Answer

The law of dominance explains that recessive traits can be hidden in heterozygous parents but expressed in offspring when two recessive alleles are inherited.

Question 9

In a dihybrid cross (AaBb × AaBb), what fraction of the F2 generation will display the dominant phenotype for both traits?

Accepted Answer

In a dihybrid cross, the F2 phenotypic ratio is 9:3:3:1; the fraction showing both dominant traits is 9/16.

Question 10

In a cross between a homozygous dominant plant (AA) and a homozygous recessive plant (aa), what will be the genotypic ratio of the F1 generation?

Accepted Answer

In a monohybrid cross between homozygous dominant (AA) and homozygous recessive (aa), all F1 offspring receive one dominant and one recessive allele, producing 100% Aa genotype.

Question 11

If a trait is controlled by a single gene with two alleles where the dominant allele (B) produces brown color and recessive allele (b) produces white color, what phenotype will appear in an individual with genotype Bb?

Accepted Answer

In heterozygous condition (Bb), the dominant allele B expresses its phenotype completely, masking the recessive allele, resulting in brown color.

Question 12

In a testcross involving a plant with dominant phenotype, the offspring ratio is 1:1 (half dominant : half recessive). What is the genotype of the plant with dominant phenotype?

Accepted Answer

A 1:1 ratio in testcross (cross with homozygous recessive aa) indicates the dominant plant is heterozygous (Aa), producing equal Aa and aa offspring.

Agniveer Army GD Genetics & Heredity

Genetics & Heredity — Practice Questions