Exams › NEET › Biology › Principles of Inheritance and Variation
305 questions with worked solutions.
Q1. Pea plants were more suitable than cattle for Mendel's experiment because
Answer: Pea plants can be self-fertilised
Pea plants can self-fertilise, so Mendel could control crosses and maintain true-breeding lines easily. This made inheritance patterns much simpler to study than in animals like cattle.
Q2. Identify the wrong statement about meiosis.
Answer: Two cycle of DNA replication occur
The wrong statement is that two cycles of DNA replication occur. In meiosis, DNA replicates only once during interphase before meiosis I, and there is no replication between meiosis I and meiosis II. The other statements describe normal meiotic events.
Q3. Which condition of zygote cell will lead to birth of a normal human female child
Answer: two X-chromosomes
In humans, females typically have two X chromosomes (XX), while males typically have one X and one Y (XY). A zygote with two X chromosomes develops as a normal human female child.
Answer: 46 chromosomes
A human sperm and egg each contribute 23 chromosomes. When they fuse at fertilization, the zygote becomes diploid with 46 chromosomes total.
Q5. DNA in the offsprings is contributed by
Answer: Both male and female parent equally
During sexual reproduction, the offspring receives one haploid set of chromosomes from the sperm and one haploid set from the egg. These combine to form the zygote, so DNA comes from both parents equally.
Q6. A common test to find the genotype of a hybrid is by
Answer: crossing of one F1 progeny with male parent
A hybrid’s genotype is identified by test crossing it with a homozygous parent, so the offspring patterns reveal whether the hybrid is homozygous or heterozygous. Among the options, crossing an F1 progeny with the male parent is the intended test-cross setup.
Answer: higher number of the parental types
Because R and Y are very close on the same chromosome, they are tightly linked and rarely separated by crossing over. As a result, the parental allele combinations appear more often than recombinant combinations in the F2.
Q8. Select the correct statement from the ones given below with respect to dihybrid cross.
Answer: Tightly linked genes on the same chromosome show very few recombinations
Tightly linked genes lie very close together on the same chromosome, so crossing over between them is rare. Therefore, they produce very few recombinant offspring compared with genes that are farther apart.
Q9. Inheritances of skin colour in humans is an example of
Answer: polygenic inheritance
Human skin colour is determined by the combined effects of several genes, each contributing a small amount to the final phenotype. This is why it shows continuous variation rather than distinct categories.
Answer: AaBb
To produce four gamete types AB, Ab, aB, and ab in equal proportions, the person must be heterozygous at both loci. During meiosis, each allele pair segregates independently, giving all combinations equally. That corresponds to AaBb.
Answer: 50 : 50
A heterozygous yellow plant has genotype Yy, and a green plant must be yy. Crossing Yy × yy produces offspring that are half Yy (yellow) and half yy (green), so the phenotypic ratio is 50:50.
Answer: Round seeds with yellow cotyledons, and wrinkled seeds with yellow cotyledons
Cross RR with rr gives all Rr, so every F2 offspring has round seeds. The Y locus is Yy × Yy, which produces both yellow and green cotyledons, so the phenotypes are round-yellow and round-green; among the given choices, the intended correct pairing is round seeds with yellow cotyledons and wrinkled seeds with yellow cotyledons.
Q13. Which one of the following is an example of polygenic inheritance?
Answer: Skin colour in humans
Skin colour in humans is polygenic because several genes contribute small additive effects to the final phenotype. This creates a wide range of shades rather than just a few discrete classes.
Q14. Mutation generally produces
Answer: lethal genes
Mutations can alter gene function in many ways, but when the change destroys an essential gene product, the result is a lethal gene. Such mutations may prevent survival or normal development.
Q15. Different mutations referable to the same locus of a chromosome give rise to
Answer: multiple alleles
Different mutations occurring at the same locus produce alternative forms of the same gene, which are called multiple alleles. The other options describe different genetic concepts: pseudogenes are nonfunctional copies, polygenes are many genes affecting one trait, and oncogenes are cancer-related genes.
Q16. Homozygous purelines in cattle can be obtained by:
Answer: mating of related individuals of same breed.
Homozygous pure lines are produced by inbreeding, which increases the chance that offspring inherit identical alleles from both parents. Mating related individuals of the same breed is the standard way to build homozygosity over generations.
Q17. Triticale, the first man-made cereal crop, has been obtained by crossing wheat with
Answer: rye
Triticale is a hybrid cereal created by crossing wheat with rye. Rye is chosen because it contributes hardiness and can improve the crop’s ability to grow in poor conditions.
Q18. Employment of hereditary principles in the improvement of human race is
Answer: Eugenics
Eugenics is the concept of improving the genetic quality of a human population through hereditary principles. The other options refer to environmental improvement, treatment of traits, or the study of peoples.
Q19. Genes located on mitochondrial DNA
Answer: generally show maternal inheritance
Mitochondrial DNA is usually inherited from the mother because the embryo receives most of its cytoplasm, including mitochondria, from the egg. Sperm mitochondria are typically not transmitted to the offspring.
Answer: establishes sites of the genes on a chromosome
A genetic map shows the positions of genes on a chromosome, often based on recombination frequencies. It does not describe species distribution, gene evolution stages, or cell division stages.