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Which of the following is the basic unit of inheritance in living organisms which controls the transfer of hereditary characteristics from parents to offspring?
1. Gene
2. Chromosome
3. DNA
4. Cell

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Correct Answer - Option 1 : Gene

The correct answer is Gene.

  • Genes are hereditary markers from which derive various characteristics like skin color, height, etc.
  • Each DNA molecule consists of sequences of Genes.
  • Each gene is a particular set of instructions for specific functions.
  • Each gene naturally consists of a sequence of nucleotides and base pairs.

Chromosome
  • Chromosomes are thread-like structures present in the nucleus.
  • These are DNA tightly coiled around a protein called histone. (just like a thread wound around a cardboard tube).
  • Chromosomes exist in pairs. Human cells contain 23 such pairs or 46 chromosomes.
  • Each chromosome is comprised of one super-long DNA molecule.
  • The DNA is coiled around histones and then many such histones are packed together to form a chromosome.
DNA
  • DNA is called the blueprint of life because it contains the genetic code which are instructions needed for an organism to grow, develop, survive, and reproduce.
  • The famous Double Helix model exists in the structure of DNA.
  • It is a twisting structure made up of 2 polymer chains. The ‘backbone’ of each chain is constituted by sugar-phosphate and connecting ladders of nitrogenous bases project inside.
    • Backbone marked with ‘S’ and ‘P’ indicating alternating sugar and phosphates.
  • The polymer chain comprises smaller monomers called nucleotides.
    • Each nucleotide has 3 parts – a sugar(ribose), a phosphate molecule, and a nitrogenous base.
  • There are 4 kinds of Nitrogenous Bases – Adenine(A), Thymine(T), Guanine(G), and Cytosine(C).
    • These bases are complementary. A attaches with T and C attaches with G to form complementary pairs that make up the connecting attachments of the double helix model.
Cell
  • Cells are the basic building blocks of all living organisms. Cells make up tissues that make up organs and then organ systems further on.
  • There are 2 kinds of cells – Prokaryotic and Eukaryotic.
    • Prokaryotic Cells – These are simpler more archaic cells lacking the most basic cell organelle including nuclei. DNA is present in the cytoplasm. Eg. Bacteria.
    • Eukaryotic Cells – These cells are well differentiated and contain many cell organelle. The genetic material is sequestered inside the nucleus. Eg. All plant and animal cells.

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