DNA

• DNA is a group of molecules that is responsible for carrying and transmitting the hereditary materials or the genetic instructions from parents to offsprings
• DNA was first recognized and identified by the Swiss biologist Johannes Friedrich Miescher in 1869 during his research on white blood cells
• The double helix structure of a DNA molecule was later discovered through the experimental data by James Watson and Francis Crick
• Finally, it was proved that DNA is responsible for storing genetic information in living organisms
• DNA Types

  • A-DNA
  • B-DNA
  • Z-DNA
• 1. DNA


  Right-handed double helix similar to B-DNA form, takes an A form under extreme conditions such as desiccation
• 1. DNA


  Most common DNA conformation, right-handed helix
• 1. DNA


  Left-handed DNA, double helix winds to the left in a zig-zag pattern, believed to play a role in gene regulation
• The basic building blocks of DNA are nucleotides, composed of a sugar group, a phosphate group, and a nitrogen base
• The DNA structure can be thought of as a twisted ladder, described as a double-helix
• All nucleic acids are made up of nucleotides, and each nucleotide is composed of sugar, phosphate groups, and nitrogen bases
• Adenine (A), Thymine (T), Guanine (G), and Cytosine (C) are four types of nitrogen bases in DNA
• A pairs with T, and C pairs with G, forming essential base pairs for the DNA's double helix structure
• Sugar forms the backbone of the DNA molecule, also called deoxyribose
• The DNA molecule consists of 4 nitrogen bases: adenine (A), thymine (T), cytosine (C), and guanine (G), forming nucleotides
• The two strands of DNA run in opposite directions and are held together by hydrogen bonds between complementary bases
• The strands are helically twisted, with each strand forming a right-handed coil, and ten nucleotides make up a single turn
• Nucleotide structure components

  • Cytosine (C)
  • Guanine (G)
  • Adenine (A)
  • Thymine (T)
• Purines

  A and G
• Pyrimidines


  C and T
• The two strands of DNA run in opposite directions
• The strands of DNA are held together by hydrogen bonds between complementary bases
• The DNA strands are helically twisted, with each strand forming a right-handed coil and ten nucleotides making up a single turn
• CHARGAFF'S RULE: The amount of A is equal to T, and the amount of C is equal to G
• Polypeptide chains are folded in secondary, tertiary, and quaternary structures to form different proteins
• DNA is the genetic material carrying all hereditary information
• Genes are small segments of DNA, mostly consisting of 250-2 million base pairs, and code for polypeptide molecules
• Replication process involves transferring genetic information between cells and generations, and equal distribution of DNA during cell division
• Mutations are changes that occur in DNA sequences
• Transcription, Cellular Metabolism, DNA Fingerprinting, and Gene Therapy are functions of DNA
• DNA replication

  1. Initiation

  2. Elongation

  3. Termination
• DNA replication is semi-conservative, where DNA makes a copy of itself
• Initiation of DNA replication

  Replication begins at the origin of replication, DNA helicase separates the two DNA strands forming the replication fork
• Elongation of DNA replication

  DNA polymerase III reads nucleotides on the template strand and adds complementary nucleotides to form a new strand. Okazaki fragments are formed on the lagging strand and sealed by ligase
• Termination of DNA replication

  Termination sequence opposite the origin terminates replication. TUS protein binds to terminator sequence halting DNA polymerase movement
• Types of RNA


  • Messenger RNA (mRNA)
  • Ribosomal RNA (rRNA)
  • Transfer RNA (tRNA)
  • Small nuclear RNA (snRNA)
  • MicroRNA (miRNA)
  • Small nucleolar RNA (snoRNA)
  • Long non-coding RNA (lncRNA)
  • Catalytic RNA (ribozymes)
• Messenger RNA (mRNA)


  It carries information from DNA to the ribosomes (site of protein synthesis) in the cell. The mRNA code sequences determine the amino acid sequence in the protein that is produced.
• Ribosomal RNA (rRNA)


  It incorporates into the ribosomes.
• Transfer RNA (tRNA)


  It is used to transfer specific amino acids to growing polypeptide chains at the ribosomal site of protein synthesis during translation.
• MicroRNA (miRNA)


  They are tiny (around 22 nucleotides) RNA molecules that regulate the expression of messenger RNA (mRNA).