Heredity – Very Short Answer Type Questions
Class: CBSE Class 10
Subject: Science — Biology
Chapter: Chapter 8 — Heredity
CBSE Board Examinations
Systematic order:
Syllabus → Learning objectives → Key concepts → Quick practice (Very Short Questions)
Syllabus → Learning objectives → Key concepts → Quick practice (Very Short Questions)
These 60 very short answer questions and answers are prepared strictly as per the NCERT syllabus for Class 10 Biology — Chapter 8: Heredity. Use them for quick revision and rapid recall for CBSE board exams.
Contents: 60 Very Short Questions with Answers — Definitions, Mendel’s work, terms, crosses, sex determination, human heredity, examples, quick practice.
1. What is heredity?
Heredity is the passing of traits from parents to offspring through genes.
2. What is variation?
Variation refers to differences among individuals of the same species.
3. Define gene.
A gene is a unit of heredity that determines a specific trait.
4. What is an allele?
An allele is an alternative form of a gene for the same trait.
5. What is genotype?
Genotype is the genetic makeup (allele combination) of an organism.
6. What is phenotype?
Phenotype is the observable physical appearance or trait of an organism.
7. Define homozygous.
Homozygous means having two identical alleles for a trait (e.g., RR or rr).
8. Define heterozygous.
Heterozygous means having two different alleles for a trait (e.g., Rr).
9. What is a dominant allele?
A dominant allele expresses its trait in the presence of another allele.
10. What is a recessive allele?
A recessive allele expresses only when two copies are present (homozygous recessive).
11. Who is Gregor Mendel?
Gregor Mendel was a scientist who discovered basic laws of inheritance using pea plants.
12. Why did Mendel use pea plants?
He used them because they had distinct traits, short generation time and could be easily cross-pollinated.
13. What is a monohybrid cross?
A monohybrid cross studies inheritance of a single trait between two parents.
14. State Mendel’s law of segregation (brief).
Each organism has two alleles that segregate during gamete formation so each gamete gets one allele.
15. State Mendel’s law of independent assortment (brief).
Alleles of different genes segregate independently during gamete formation (for genes on different chromosomes).
16. What ratio did Mendel observe in F2 of a monohybrid cross?
He observed a phenotypic ratio of 3:1 (dominant:recessive) in F2.
17. Give an example of a dominant trait in pea plants.
Round seeds (R) are dominant over wrinkled seeds (r).
18. Give an example of a recessive trait in pea plants.
White flower colour (when purple is dominant) or wrinkled seeds (r) are recessive traits.
19. What is a Punnett square?
A Punnett square is a diagram used to predict genotypic and phenotypic ratios of offspring.
20. What is co-dominance? Give one example.
Co-dominance is when both alleles express equally in heterozygote; example: blood group AB.
21. What is incomplete dominance?
Incomplete dominance is when heterozygote shows intermediate phenotype (e.g., red × white → pink).
22. Define multiple alleles.
Multiple alleles are more than two alternative forms of a gene in a population (e.g., ABO blood group).
23. What are sex chromosomes?
Sex chromosomes are chromosome pair that determines sex (X and Y in humans).
24. State the human sex chromosome combinations for male and female.
Female: XX; Male: XY.
25. Which parent determines the sex of the child?
The father determines sex because his sperm carries either X or Y chromosome.
26. What is a phenotype ratio?
Phenotype ratio is the proportion of different observable traits among offspring (e.g., 3:1).
27. What is a genotype ratio?
Genotype ratio is the proportion of different genetic combinations among offspring (e.g., 1:2:1).
28. What is meant by pure-breeding (true-breeding)?
Pure-breeding organisms produce offspring with same trait for many generations (homozygous).
29. What are gametes?
Gametes are sex cells (sperm and egg) that carry one allele for each gene.
30. What is fertilisation?
Fertilisation is the fusion of male and female gametes to form a zygote.
31. Define mutation (brief).
A mutation is a change in DNA sequence that may cause variation.
32. What is genetic variation?
Genetic variation is differences in DNA among individuals of a species.
33. Give one environmental example that causes variation.
Nutrition affecting height or flower colour variation due to soil acidity.
34. What is polygenic inheritance?
Polygenic inheritance is when many genes contribute to a single trait (e.g., human height).
35. Name a sex-linked trait in humans.
Red-green colour blindness is a common sex-linked trait.
36. What is haemophilia (brief)?
Haemophilia is a sex-linked bleeding disorder usually caused by a recessive allele on X chromosome.
37. What are autosomes?
Autosomes are non-sex chromosomes present in pairs in both sexes.
38. What is an inherited disorder?
An inherited disorder is a disease transmitted from parents to offspring via genes.
39. Give one example of a single-gene human trait.
Widow’s peak (hairline) or earlobe attachment (free or attached) are single-gene traits.
40. What is chromosomal basis of sex determination?
Sex is determined by presence/absence of particular sex chromosomes (XX or XY in humans).
41. What does 1:2:1 genotypic ratio indicate in monohybrid F2?
It indicates genotypes TT : Tt : tt in ratio 1 : 2 : 1 among F2 offspring.
42. What is a test cross (brief)?
A test cross is breeding an individual with unknown genotype with a homozygous recessive to find its genotype.
43. What is back cross?
Back cross is crossing offspring back with one of its parents or genetically similar organism.
44. What is hybrid vigour (heterosis) (brief)?
Hybrid vigour is improved or increased function shown by hybrid offspring compared to parents.
45. Why are Mendel’s results quantitative?
Because he counted large numbers of offspring and reported ratios, giving numerical evidence for inheritance.
46. What does 'expressed' mean in genetics?
Expressed means the trait is visible in the phenotype due to action of an allele.
47. What is an example of discrete variation?
Pea seeds being either round or wrinkled (no intermediate) is discrete variation.
48. What is continuous variation?
Continuous variation shows a range of differences, e.g., human height or skin colour.
49. Give one agricultural importance of heredity.
Heredity allows selective breeding to improve crop yield and disease resistance.
50. What is a trait?
A trait is any observable characteristic of an organism (e.g., eye colour).
51. Give one example of non-Mendelian inheritance taught in Class 10.
Co-dominance in blood groups (AB) is an example discussed at basic level.
52. What is 'pure line' in Mendel’s experiments?
A pure line is a true-breeding strain showing same trait for many generations (homozygous).
53. What does 'segregate' mean?
To segregate means alleles separate into different gametes during meiosis.
54. Why is father called the heterogametic sex in humans?
Because males produce two types of gametes (X-bearing and Y-bearing sperm), determining sex.
55. What is a zygote?
A zygote is the fertilised egg formed by fusion of sperm and egg, containing full set of chromosomes.
56. What is the role of chromosomes in heredity?
Chromosomes carry genes; they ensure transmission of genetic information from parents to offspring.
57. What is the basic cause of inherited variation?
Changes or differences in genes (mutations and recombination) are basic causes of inherited variation.
58. What is the significance of Mendel’s experimental method?
His controlled crosses and quantitative analysis established predictable patterns in inheritance.
59. Mention one limitation of Mendel’s laws.
They do not apply when genes are linked on same chromosome or when multiple alleles/incomplete dominance occur.
60. Give one quick revision tip for this chapter.
Practice Punnett squares for monohybrid crosses and memorise key definitions and Mendel’s laws.
Note: Keep answers concise in the exam for very short answer questions. Use simple examples (pea plant traits, human traits) and neat Punnett squares where required.