Biology Class 12 NCERT Solutions: Chapter 6 Molecular Basis of Inheritance Part 4 (For CBSE, ICSE, IAS, NET, NRA 2023)

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Q. 13 What is DNA fingerprinting? Mention its application.

Answer:

  • DNA fingerprinting is a technique used to identify and analyses the variations in various individuals at the level of DNA.
  • It is based on variability and polymorphism in DNA sequences.

Application

  • It is used in forensic science to identify potential crime suspects.
  • It is used to establish paternity and family relationships.
  • It is used to identify and protect the commercial varieties of crops and livestock.
  • It is used to find out the evolutionary history of an organism and trace out the linkages between groups of various organisms.

Q. 14 Briefly describe the following:

(a) Transcription

(b) Polymorphism

(c) Translation

(d) Bioinformatics

Answer:

(a) Transcription

  • Transcription is the process of synthesis of RNA from DNA template. A segment of DNA gets copied into mRNA during the process.
  • The process of transcription starts at the promoter region of the template DNA and terminates at the terminator region.
  • The segment of DNA between these two regions is known as transcription unit. The transcription requires RNA polymerase enzyme, a DNA template, four types of ribonucleotides, and certain cofactors such as .
  • The three important events that occur during the process of transcription are as follows.
  • Initiation
  • Elongation
  • Termination
  • The DNA-dependent RNA polymerase and certain initiation factors bind at the double stranded DNA at the promoter region of the template strand and initiate the process of transcription.
  • RNA polymerase moves along the DNA and leads to the unwinding of DNA duplex into two separate strands. Then, one of the strands, called sense strand, acts as template for mRNA synthesis.
  • The enzyme, RNA polymerase, utilizes nucleoside triphosphates (dNTPs) as raw material and polymerizes them to form mRNA according to the complementary bases present on the template DNA.
  • This process of opening of helix and elongation of polynucleotide chain continues until the enzyme reaches the terminator region.
  • As RNA polymerase reaches the terminator region, the newly synthesized mRNA transcripted along with enzyme is released.
  • Another factor called terminator factor is required for the termination of the transcription.
Process of Transcription

(b) Polymorphism

  • Polymorphism is a form of genetic variation in which distinct nucleotide sequence can exist at a particular site in a DNA molecule.
  • This heritable mutation is observed at a high frequency in a population. It arises due to mutation either in somatic cell or in the germ cells.
  • The germ cell mutation can be transmitted from parents to their offsprings. This results in accumulation of various mutations in a population, leading to variation and polymorphism in the population.
  • This plays a very important role in the process of evolution and speciation.