Summary

  • Nucleic acids are long polymers of nucleotides.
  • While DNA stores genetic information, RNA mostly helps in transfer and expression of information.
  • Though DNA and RNA both function as genetic material, but DNA being chemically and structurally more stable is a better genetic material.
  • However, RNA is the first to evolve and DNA was derived from RNA.
  • The hallmark of the double stranded helical structure of DNA is the hydrogen bonding between the bases from opposite strands.
  • The rule is that Adenine pairs with Thymine through two H-bonds, and Guanine with Cytosine through three H-bonds. This makes one strand complementary to the other.
  • The DNA replicates semiconservatively, the process is guided by the complementary H-bonding.
  • A segment of DNA that codes for RNA may in a simplistic term can be referred as gene.
  • During transcription also, one of the strands of DNA acts a template to direct the synthesis of complementary RNA.
  • In bacteria, the transcribed mRNA is functional, hence can directly be translated. In eukaryotes, the gene is split.
  • The coding sequences, exons, are interrupted by non-coding sequences, introns. Introns are removed and exons are joined to produce functional RNA by splicing.
  • The messenger RNA contains the base sequences that are read in a combination of three (to make triplet genetic code) to code for an amino acid.
  • The genetic code is read again on the principle of complementarity by tRNA that acts as an adapter molecule.
  • There are specific tRNAs for every amino acid. The tRNA binds to specific amino acid at one end and pairs through H-bonding with codes on mRNA through its anticodons.
  • The site of translation (protein synthesis) is ribosomes, which bind to mRNA and provide platform for joining of amino acids.
  • One of the rRNA acts as a catalyst for peptide bond formation, which is an example of RNA enzyme (ribozyme).
  • Translation is a process that has evolved around RNA, indicating that life began around RNA.
  • Since, transcription and translation are energetically very expensive processes, these have to be tightly regulated. Regulation of transcription is the primary step for regulation of gene expression.
  • In bacteria, more than one gene is arranged together and regulated in units called as operons.
  • Lac operon is the prototype operon in bacteria, which codes for genes responsible for metabolism of lactose.
  • The operon is regulated by the amount of lactose in the medium where the bacteria are grown.
  • Therefore, this regulation can also be viewed as regulation of enzyme synthesis by its substrate.
  • Human genome project was a mega project that aimed to sequence every base in human genome.
  • This project has yielded much new information. Many new areas and avenues have opened up as a consequence of the project.
  • DNA Fingerprinting is a technique to find out variations in individuals of a population at DNA level.
  • It works on the principle of polymorphism in DNA sequences. It has immense applications in the field of forensic science, genetic biodiversity and evolutionary biology.

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