All Free Biology MCQs with Answers

• A. Down syndrome
• B. Klinefelter syndrome
• C. Phenylketonuria
• D. Turner syndrome

Explanation: Phenylketonuria (PKU) is a genetic disorder that is caused by a point mutation, specifically a mutation in a single gene known as the PAH…

• A. Johnson
• B. Corren
• C. Tschmarch
• D. Purkinje

Explanation: The term "Gene" was coined by the Danish botanist Wilhelm Johannsen. He introduced the term 'gene' in the early 20th century to describe…

• A. result of mitosis
• B. result of meiosis
• C. actual outcome of a cross
• D. probable outcome of cross

Explanation: A punnett square is always used to determine the POSSIBLE OUTCOME of a cross and never an actual one because an actual one can never be…

• A. 0%
• B. 25%
• C. 50%
• D. 75%

Explanation: There is zero possibility that their offspring will have a B-negative blood type

• A. Homozygous
• B. Monoecious
• C. Heterozygous
• D. Dioecious

Explanation: An individual with contrasting alleles is called Heterozygous. This means that the organism has two different alleles (such as Tt) for a…

• A. 4
• B. 3
• C. 2
• D. 9

Explanation: In a dihybrid cross, two traits are considered, each with two alleles. The result is a 4x4 Punnett square with 16 possible genotypes.

• A. Monozygous
• B. Homozygous
• C. Heterozygous
• D. Multizygous

Explanation: Heterozygous organisms possess two different alleles for a specific trait, which allows them to exhibit similar phenotypes (observable…

• A. One
• B. Two
• C. Three
• D. Four

Explanation: When crossing two alleles 'A' and 'a', the potential genotypes that can be formed are AA, Aa, and aa.

• A. Sickle cell anemia
• B. Cooley's anemia
• C. Microcytic anemia
• D. Nutritional anemia

Explanation: Thalassaemia major is also known as Cooley's anemia, named after Thomas B.

• A. Co-dominance
• B. Over dominance
• C. Epistasis
• D. Incomplete dominance

Explanation: In incomplete dominance, the heterozygous phenotype is a blend of the two homozygous phenotypes, resulting in a phenotypic ratio that…

• A. Test cross
• B. Interbreeding
• C. Epistasis
• D. Hybridization

Explanation: Hybridization is the process of an animal or plant breeding with an individual of another species or variety. So D is the correct option.

• A. 50%
• B. 25%
• C. 75%
• D. 100%

Explanation: A cross between two heterozygous tall plants results in 25% homozygous tall, 50% heterozygous tall, and 25% dwarf plants.

• A. Overdominance
• B. Complete dominance
• C. Incomplete dominance
• D. Co-dominance

Explanation: The correct answer is Overdominance. In the case of fluorescent pigments in the eyes of fruit flies, heterozygotes may exhibit a more…

• A. New
• B. De novo
• C. Drift
• D. Both (a) & (b)

Explanation: The correct answer is De novo mutation. These mutations occur in the germ cells or immediately after fertilization and are not inherited…

• A. Multiple alleles and incomplete dominance
• B. Co dominance and incomplete dominance
• C. Incomplete dominance only
• D. Multiple alleles and co dominance

Explanation: The human ABO blood group system exhibits codominance. It consists of three alleles A, B, and O. Both A and B show codominance

• A. Dominance
• B. Co dominance
• C. Multiple alleies
• D. Incomplete dominance

Explanation: Codominance means that no allele can block or mask the expression of the other allele.

• A. Complete dominance
• B. Over dominance
• C. Co-dominance
• D. Incomplete dominance

Explanation: When we talk about the dominance of relations in the 4 o'clock plant, it can be described in terms of incomplete dominance.

• A. Dihybrid
• B. Dual hybrid
• C. Heterotype
• D. Hybrid

Explanation: A hybrid is an organism that has parents of different breeds, varieties, or species.

• A. 3:1 between son and daughter
• B. 1:3 between son and daughter
• C. 1:1 between son and daughter
• D. None of the above

Explanation: The chances for having a son or daughter in human birth are often estimated to be around 50% for each gender.

• A. Uterus
• B. Ovaries
• C. Graffian follicles
• D. Urinary bladder

Explanation: In women, FSH helps manage the menstrual cycle and stimulates the ovaries to produce eggs.