Q. If a vaccine reduces the risk of infection by 75%, what is the probability of infection after vaccination if the initial probability of infection is 0.2? (2020)
A.
0.05
B.
0.1
C.
0.15
D.
0.2
Solution
The probability of infection after vaccination = Initial probability × (1 - reduction) = 0.2 × (1 - 0.75) = 0.2 × 0.25 = 0.05.
Q. If a woman with blood type A (genotype AO) has a child with a man with blood type B (genotype BO), what are the possible blood types of their child?
A.
A, B, AB, O
B.
A, B, AB
C.
A, O
D.
B, O
Solution
The possible blood types from AO x BO are A, B, AB, and O.
Q. In a certain plant species, tall (T) is dominant over short (t). If a homozygous tall plant is crossed with a homozygous short plant, what will be the genotype of the offspring?
A.
TT
B.
Tt
C.
tt
D.
Tt and tt
Solution
The homozygous tall plant (TT) crossed with a homozygous short plant (tt) will produce all offspring with the genotype Tt.
Q. In a certain species of fruit flies, the allele for red eyes (R) is dominant over the allele for white eyes (r). If two red-eyed flies, one homozygous (RR) and one heterozygous (Rr), are crossed, what percentage of the offspring will have white eyes?
A.
0%
B.
25%
C.
50%
D.
100%
Solution
The cross RR x Rr will produce all red-eyed offspring (100% R). Thus, 0% will have white eyes.
Q. In a certain species of pea plants, round seeds (R) are dominant over wrinkled seeds (r). If a round seed plant with genotype Rr is crossed with a wrinkled seed plant (rr), what is the expected genotype ratio of the offspring?
A.
1:1
B.
3:1
C.
1:2:1
D.
2:1
Solution
The cross Rr x rr results in 1 Rr (round) and 1 rr (wrinkled), giving a genotype ratio of 1:1.
Q. In a certain species, the allele for blue eyes (b) is recessive to the allele for brown eyes (B). If two heterozygous brown-eyed individuals (Bb) have children, what is the probability that a child will have blue eyes?
A.
0%
B.
25%
C.
50%
D.
75%
Solution
The cross Bb x Bb results in a 1/4 chance of bb (blue eyes), so the probability is 25%.
Q. In a certain species, the allele for blue eyes (b) is recessive to the allele for brown eyes (B). If a brown-eyed man (Bb) marries a blue-eyed woman (bb), what is the probability that their child will have blue eyes?
A.
0%
B.
25%
C.
50%
D.
100%
Solution
The cross Bb x bb results in 50% Bb (brown) and 50% bb (blue), so the probability of having a blue-eyed child is 50%.
Q. In a certain species, the allele for blue flowers (B) is dominant over the allele for white flowers (b). If two blue-flowered plants, one homozygous (BB) and one heterozygous (Bb), are crossed, what percentage of the offspring will have white flowers?
A.
0%
B.
25%
C.
50%
D.
100%
Solution
The cross BB x Bb will produce 100% blue flowers (BB or Bb), so 0% will have white flowers.
Q. In a certain species, the allele for blue flowers (B) is dominant over the allele for white flowers (b). If two blue-flowered plants, both heterozygous (Bb), are crossed, what is the expected phenotypic ratio of the offspring?
A.
1:1
B.
3:1
C.
1:2:1
D.
2:1
Solution
The cross Bb x Bb results in a phenotypic ratio of 3 blue (BB or Bb) to 1 white (bb), which is 3:1.
Q. In a certain species, the allele for long tails (L) is dominant over the allele for short tails (l). If a long-tailed individual is crossed with a short-tailed individual, what is the expected genotype of the offspring if the long-tailed individual is heterozygous?
A.
LL
B.
Ll
C.
ll
D.
LL or Ll
Solution
The cross Ll x ll will produce offspring with genotypes Ll and ll, so the expected genotype is Ll.
Q. In a certain species, the allele for tall plants (T) is dominant over the allele for short plants (t). If a tall plant (Tt) is crossed with a short plant (tt), what is the expected genotypic ratio of the offspring?
A.
1:1
B.
3:1
C.
1:2:1
D.
2:1
Solution
The cross Tt x tt results in a genotypic ratio of 1 Tt (tall) to 1 tt (short), which is 1:1.
Q. In a certain species, the allele for tall plants (T) is dominant over the allele for short plants (t). If two heterozygous tall plants (Tt) are crossed, what is the expected phenotypic ratio of the offspring?
A.
1:2:1
B.
3:1
C.
9:3:3:1
D.
1:1
Solution
The expected phenotypic ratio from Tt x Tt is 3 tall: 1 short, which is a 3:1 ratio.
Q. In a clinical trial, 60% of patients showed improvement after treatment. If 150 patients were treated, how many patients are expected to show improvement? (2022)
Q. In a dihybrid cross between two pea plants, one with genotype AaBb and the other with genotype Aabb, what fraction of the offspring will be homozygous recessive for both traits?
A.
1/16
B.
1/8
C.
1/4
D.
1/2
Solution
The cross AaBb x Aabb results in 1/8 of the offspring being aabb (homozygous recessive for both traits).
Q. In a dihybrid cross between two plants, one with genotype AaBb and the other with genotype Aabb, what fraction of the offspring will be expected to show the dominant phenotype for both traits?
A.
1/4
B.
1/2
C.
3/4
D.
1/8
Solution
The cross AaBb x Aabb results in 1/4 AABB, 1/4 AABb, 1/4 AaBb, and 1/4 Aabb. Only AABB, AABb, and AaBb show the dominant phenotype for both traits, which is 3 out of 8, hence 3/8.
Q. In a genetic experiment, a plant with genotype AaBb is crossed with another plant of genotype Aabb. What is the probability of obtaining an offspring with genotype Aabb?
A.
1/4
B.
1/2
C.
3/4
D.
1/8
Solution
The possible genotypes from the cross AaBb x Aabb are AaBb, Aabb, AABb, and Aabb. The probability of Aabb is 1/2.
Q. In a genetic study, if a trait is controlled by a single gene with two alleles, how many different genotypes can be formed from two heterozygous parents?
A.
1
B.
2
C.
3
D.
4
Solution
From two heterozygous parents (Aa x Aa), the possible genotypes are AA, Aa, and aa, resulting in 3 different genotypes.
Q. In a genetic study, if a trait is controlled by a single gene with two alleles, where one allele is completely dominant over the other, what is the expected genotypic ratio in the offspring of a monohybrid cross?
A.
1:2:1
B.
3:1
C.
1:1
D.
9:3:3:1
Solution
The expected genotypic ratio from a monohybrid cross is 1:2:1.
Q. In a genetic study, if a trait is controlled by a single gene with two alleles, where one allele is completely dominant over the other, what type of inheritance pattern is this?
A.
Codominance
B.
Incomplete dominance
C.
Complete dominance
D.
Polygenic inheritance
Solution
This describes complete dominance, where one allele completely masks the effect of the other.
Biology is a crucial subject for students preparing for school exams and competitive tests in India. Understanding biological concepts not only helps in grasping the fundamentals of life sciences but also enhances your ability to tackle objective questions effectively. Practicing MCQs and objective questions in Biology is essential for scoring better, as it allows you to apply your knowledge and identify important questions that frequently appear in exams.
What You Will Practise Here
Cell Structure and Function
Genetics and Heredity
Human Anatomy and Physiology
Plant Biology and Ecology
Microbiology and Biotechnology
Evolution and Biodiversity
Important definitions and key formulas
Exam Relevance
Biology is a significant part of the curriculum for CBSE, State Boards, NEET, and JEE. In these exams, you can expect a variety of question patterns, including multiple-choice questions that test your understanding of key concepts, definitions, and applications of biological theories. Familiarity with important Biology MCQ questions will give you an edge in both school assessments and competitive exams.
Common Mistakes Students Make
Confusing similar terms, such as mitosis and meiosis.
Overlooking the importance of diagrams in understanding processes.
Misinterpreting questions that require application of concepts rather than rote memorization.
Neglecting to review key definitions and their implications.
FAQs
Question: What are the best ways to prepare for Biology MCQs? Answer: Regular practice with objective questions, reviewing key concepts, and understanding diagrams are effective strategies.
Question: How can I improve my accuracy in answering Biology objective questions? Answer: Focus on understanding concepts rather than memorizing facts, and practice with past exam papers to familiarize yourself with question patterns.
Start solving practice MCQs today to test your understanding and boost your confidence in Biology. Remember, consistent practice is the key to mastering this subject and achieving your exam goals!
Soulshift Feedback×
On a scale of 0–10, how likely are you to recommend
The Soulshift Academy?
