In a monohybrid cross between two heterozygous plants (Aa × Aa), what is the phenotypic ratio in the F2 generation?
Answer: B
For a monohybrid cross Aa × Aa, the F2 generation shows 3 dominant : 1 recessive phenotypic ratio, following Mendel's law of segregation.
Q.2Easy
What is the chromosome number in a human somatic cell?
Answer: B
Human somatic cells are diploid with 46 chromosomes (23 pairs). Gametes contain 23 chromosomes (haploid).
Q.3Easy
Which law states that factors (alleles) segregate during gamete formation?
Answer: B
Mendel's Law of Segregation describes how alleles separate during meiosis, resulting in each gamete receiving only one allele for each gene.
Q.4Easy
A test cross involves crossing an organism with a dominant phenotype with a _______ individual.
Answer: C
A test cross pairs an individual showing the dominant phenotype with a homozygous recessive individual to determine the genotype of the dominant phenotype.
Q.5Medium
In a dihybrid cross (AaBb × AaBb), what is the expected phenotypic ratio in F2?
Answer: B
The classical dihybrid cross ratio is 9:3:3:1, following Mendel's Law of Independent Assortment for two independently assorting genes.
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Q.6Medium
What is the term for genes located on the X chromosome?
Answer: B
Sex-linked genes are located on sex chromosomes, particularly the X chromosome. X-linked traits show different inheritance patterns in males and females.
Q.7Medium
Color blindness in humans is an X-linked recessive trait. If a carrier female (XᶜX) marries a normal male (XᶜY), what percentage of their sons will be color blind?
Answer: C
Cross: XᶜX × XᶜY produces: XᶜXᶜ (normal daughter), XᶜX (carrier daughter), XᶜY (color blind son), XᶜY (normal son). 50% of sons are color blind.
Q.8Medium
Which of the following is an example of incomplete dominance?
Answer: B
Incomplete dominance occurs when the heterozygote shows an intermediate phenotype. Red × white flowers → pink flowers is a classic example.
Q.9Medium
What is codominance?
Answer: B
In codominance, both alleles contribute equally to the phenotype. Example: AB blood group where both A and B antigens are expressed.
Q.10Medium
ABO blood group system in humans shows which type of inheritance?
Answer: C
ABO blood groups show codominance. Alleles Iᴬ and Iᴮ are dominant over i but are codominant to each other, producing four blood types.
Q.11Medium
Which of the following best describes a mutation?
Answer: B
A mutation is any sudden, spontaneous change in the DNA sequence that can be inherited. It provides genetic variation for natural selection.
Q.12Medium
Linkage is the phenomenon where genes are inherited together because they are located on the same ______.
Answer: C
Linked genes are located close together on the same chromosome and tend to be inherited together, violating the Law of Independent Assortment.
Q.13Medium
A plant breeder crosses two tall pea plants and obtains both tall and short offspring. This indicates that tall is _______ over short.
Answer: C
If two tall plants produce short offspring, both parents must be heterozygous (Aa). The short offspring (aa) proves tall is dominant.
Q.14Medium
In humans, if both parents are carriers of cystic fibrosis (Aa), what is the probability their child will have the disease (aa)?
Answer: A
Cross: Aa × Aa produces AA (25%), Aa (50%), aa (25%). Only homozygous recessive (aa) individuals have cystic fibrosis.
Q.15Medium
Which type of genetic disorder shows autosomal dominant inheritance?
Answer: B
Huntington's disease is an autosomal dominant disorder. A single copy of the dominant allele causes the disease phenotype.
Q.16Hard
A man with hemophilia (XʰY) marries a normal woman (XʰXʰ). All their daughters will be _______ and all sons will be _______.
Answer: C
Cross: XʰY × XʰXʰ produces XʰXʰ (carrier daughters) and XʰY (normal sons). Daughters carry one recessive allele but are phenotypically normal.
Q.17Hard
In Drosophila, white eye color (w) is recessive to red eye color (w⁺) and is X-linked. If a white-eyed female is crossed with a red-eyed male, what will be the eye color of the F1 females?
Answer: B
Cross: ww × w⁺Y produces w⁺w (heterozygous females with red eyes) and wY (white-eyed males). F1 females are red-eyed.
Q.18Hard
A cross between a plant with genotype AaBb and a plant with genotype aabb produces 160 offspring. Due to linkage between genes A and B (20 map units apart), the expected frequency of AaBb offspring will be approximately ______.
Answer: C
With 20 map units distance, recombination frequency is 20%. Parental types (AB/ab) = 40% each, recombinants = 10% each. AaBb from coupling = 40 out of 160.
Q.19Medium
In a dihybrid cross between two heterozygous pea plants (AaBb × AaBb), what is the probability of obtaining an offspring with at least one dominant trait for both genes?
Answer: A
In a dihybrid cross, the 9:3:3:1 ratio indicates that 9 out of 16 offspring have dominant phenotypes for both traits (A_B_). This represents 169 probability.
Q.20Medium
A woman with normal vision (carrier for color blindness) marries a man with normal vision. What percentage of their sons will be color blind?
Answer: C
The carrier mother (XᴮXᵇ) × normal father (XᴮY) produces sons with 50% probability of being XᵇY (color blind), as sons receive Xᵇ from mother in half the cases.
