NCERTier-Key Points

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  • Novological Mendel

    During Mendel’s investigations into inheritance patterns it was for the first time that statistical analysis and mathematical logic were applied to problems in biology.

  • Credible Mendel

    His experiments had a large sampling size, which gave greater credibility to the data that he collected. More in Our App. Download Now.

  • Consistent Mendel

    The confirmation of his inferences from experiments on successive generations of his test plants, proved that his results pointed to general Rules of inheritance rather than being unsubstantiated ideas.

Key Point - 2

  • Mendel's Factor

    Mendel proposed that something was being stably passed down, unchanged, from parent to offspring through the gametes, over successive generations. He called these things as ‘factors’..

  • Gene now a days..

    Genes are the units of inheritance. They contain the information that is required to express a particular trait in an organism. Genes which code for a pair of contrasting traits are known as alleles, i.e., they are slightly different forms of the same gene.. More in Our App. Download Now.

  • Mendel's Law of Dominance

    (i) Characters are controlled by discrete units called factors. (ii) Factors occur in pairs. (iii) In a dissimilar pair of factors one member of the pair dominates (dominant) the other (recessive)..

Law of Segregation

This law is based on the fact that the alleles do not show any blending and that both the Traits are recovered as such in the F2 generation though one of these is not seen at the F1 stage. Though the parents contain two alleles during gamete formation, the factors or alleles of a pair segregate from each other such that a gamete receives only one of the two factors.

Of course, a homozygous parent produces all gametes that are similar while a heterozygous one produces two kinds of gametes each having one allele with equal proportion..

Based on his observations on monohybrid crosses Mendel proposed two general rules to consolidate his understanding of inheritance in monohybrid crosses. Today these rules are called the Principles or Laws of Inheritance: the First Law or Law of Dominance and the Second Law or Law of Segregation.


  • Seven years (1856-1863).

    Gregor Mendel, conducted hybridisation experiments on garden peas.
  • 14 contrasting traits

    of True-breeding pea selected by Mendel.
  • On Chromosome 7

    Seed shape - Round/wrinkled
  • On Chromosome 5

    Pod colour- Green/yellow
  • On Chromosome 1

    Seed colour and Flower Colour.
  • On Chromosome 4

    All Remaining Characters
  • 50% Chance of a gamete containing..

    either allele T or t
  • Test cross.

    between F1 or F2 tall plant and dwarf plant.
  • 3:1 Phenotypic & 1:2:1 Genotypic Ratio

    of Monohybrid Cross.

Key Words

Inheritance is the process by which characters are passed on from parent to progeny; it is the basis of heredity. Variation is the degree by which progeny differ from their parents.



A Truebreeding line is one that, having undergone continuous self-pollination, shows the stable trait inheritance and expression for several generations.

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