CBSE Class 10 Science Chapter 8 Heredity — 20 MCQs with Answers

Gregor Mendel's work on garden peas laid the foundation for classical genetics. He chose seven contrasting traits — such as tall versus dwarf plants, round versus wrinkled seeds — and crossed pure-breeding lines to observe inheritance patterns across generations. His Law of Dominance states that in a heterozygote one allele masks the other. The Law of Segregation explains that allele pairs separate during gamete formation, ensuring each gamete carries only one allele per gene. The Law of Independent Assortment applies when genes for different traits are on separate chromosomes, so they sort independently. NCERT introduces these laws through monohybrid and dihybrid crosses, and CBSE questions often ask you to predict offspring ratios or identify which law explains a given cross. Mastering the 3:1 and 9:3:3:1 ratios is non-negotiable for scoring full marks.

NCERT clearly distinguishes between inherited traits — which are genetically determined and passed from parents to offspring through DNA — and acquired traits, which develop during an organism's lifetime due to environmental factors and cannot be transmitted. For example, a bodybuilder's muscles are acquired; they do not appear in their children. Eye colour, blood group, and attached earlobes are inherited. CBSE likes to test this distinction through assertion-reason questions or scenario-based MCQs. A classic trick question presents a trait acquired through surgery or training and asks whether it will appear in the next generation. Remember: only changes in germ-cell DNA are heritable; somatic modifications are not.

In humans, sex is determined by the 23rd pair of chromosomes. Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY). During fertilization, the mother always contributes an X chromosome from her egg, and the father contributes either an X or a Y from his sperm. If the sperm carries X, the child is XX (female); if it carries Y, the child is XY (male). This results in a roughly 1:1 sex ratio. CBSE questions often present a Punnett square for sex determination and ask for the probability of male or female offspring, or they pose assertion-reason statements about whether the mother or father determines the child's sex. Understanding that the father's sperm decides the sex is crucial for these MCQs.

Variation refers to differences among individuals of a species. NCERT emphasizes that variation arises through two main mechanisms: sexual reproduction (crossing over and independent assortment during meiosis) and mutation (random changes in DNA). Variation is the raw material for evolution; it allows populations to adapt to changing environments. Asexual reproduction produces clones with minimal variation, whereas sexual reproduction shuffles alleles and creates novel combinations. CBSE questions often ask why variation is important for a species' survival or which mode of reproduction generates more variation. Real-world examples include antibiotic resistance in bacteria (a survival advantage conferred by a mutation) and the diversity of dog breeds (artificial selection acting on genetic variation).

CBSE increasingly includes application-based and higher-order thinking questions that test your ability to interpret data, analyze crosses, or apply Mendelian principles to novel scenarios. These MCQs may present a pedigree chart, a Punnett square with missing data, or a case study involving inheritance patterns in humans or plants. They assess whether you can transfer knowledge rather than simply recall definitions. For instance, a question might describe a genetic disorder and ask you to predict the likelihood of it appearing in offspring, or it might give the phenotypic ratio of a cross and ask you to deduce the genotypes of the parents. Practicing such questions sharpens analytical skills and prepares you for the 3-mark and 5-mark descriptive questions that follow the MCQ section.

Students often lose marks in Heredity MCQs due to a handful of recurring errors. First, confusing phenotype (observable trait) with genotype (genetic makeup) leads to incorrect ratio interpretations. Always write out the Punnett square on scrap paper if you are unsure. Second, misidentifying the type of cross: a test cross is Tt × tt (to reveal an unknown genotype), while a monohybrid cross is Tt × Tt. Third, overlooking the phrase 'all offspring' versus 'probability' — the former may indicate a homozygous parent. Fourth, in assertion-reason MCQs, students sometimes mark (B) when the reason does explain the assertion; read carefully. Fifth, rushing through sex-determination questions and forgetting that the mother always contributes X. Practice timed MCQ sets, review your mistakes immediately, and maintain a one-page formula sheet with ratios (3:1, 1:2:1, 9:3:3:1) and key definitions.

Understanding Heredity requires visualizing crosses, interpreting Punnett squares, and connecting abstract genetic principles to real-world traits. CBSETUTOR.ai provides a 24×7 AI tutor that accepts photo uploads of any MCQ or diagram from your textbook or test paper. Snap a picture of a dihybrid cross you don't understand, and the AI walks you through allele segregation step by step. It explains why a 9:3:3:1 ratio emerges, which law applies, and how to quickly eliminate wrong options. For ₹999 per month — covering all subjects across Classes 6 to 12 — you get unlimited doubt solving, chapter-wise practice sets, and instant feedback. The platform recognizes NCERT terminology, so explanations match your syllabus exactly. A 3-day free trial lets you test the AI on Chapter 8 Heredity MCQs before committing. Thousands of CBSE students use CBSETUTOR.ai to convert confusion into confidence, especially in chapters heavy on diagrams and ratios.

The CBSE Class 10 Science paper typically includes 16 to 20 MCQs, worth 1 mark each, covering all units. Heredity MCQs appear in Section A and must be answered quickly to leave time for short and long answers. Start by reading the question stem carefully, underlining key terms such as 'homozygous', 'F₂ generation', or 'sex chromosomes'. Eliminate obviously incorrect options first. If two options seem plausible, sketch a mini Punnett square in the margin or apply the relevant Mendelian ratio. For assertion-reason MCQs, evaluate the assertion independently, then the reason, and finally check if the reason explains the assertion. Never leave an MCQ blank — there is no negative marking. If you are unsure, choose the option that aligns with NCERT language and avoid extremes like 'always' or 'never'. Budget roughly 30 seconds per MCQ, mark challenging ones for review, and return to them after completing easier questions. Time management and accuracy together determine your objective-section score.