How are traits expressed?



  • DNA in the cells provides information for the proteins to be made.
  • I nformation for each protein is given by sections of DNA called genes.
  • The section that provides information for one protein is called the gene for that protein.

Let us see how exactly this works:

Consider the trait, height of the plant ,

  • Certain hormones (chemicals) trigger plant growth
  • Thus the height of the plant depends on the amount of hormone produced
  • Now:


  • Thus genes control traits or characteristics.


According to Mendel’s experiment, 

  • We know that during sexual reproduction, both parents contribute equally to the DNA of the progeny /offspring.
  • Both parents contribute one copy of each gene and thus both parents determine the trait in the progeny.
  • So each progeny will have 2 gene sets ; one from each parent.


The germ cells (cells involved in sexual reproduction), should have only one copy of the genes.

This is achieved by each cell obtaining  two copies of each chromosome , one from the male and one from the female parent.


  • The germ cells take one chromosome from each pair .
  • When two germ cells combine during sexual reproduction, the chromosome number is restored in the progeny.


  • This ensures the stability of the DNA of the species.

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Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 13 years and a teacher from the past 17 years. He teaches Science, Economics, Accounting and English at Teachoo