Watson & Crick's DNA Model

DNA Structure

• DNA is composed of two right-handed polynucleotide chains that coil around each other to form a helical structure with an axis of symmetry.
• The chains are antiparallel, meaning they run in opposite directions.
• Purine and pyrimidine bases are hydrophobic and occupy the interior space, while deoxyribose sugar and phosphate backbone are hydrophilic and external.
• Base pairs are planar and almost perpendicular to the axis of the helix.

Hydrogen Bonding

• Hydrogen bonding occurs between purine base on one chain and pyrimidine base on the other, or vice versa.
• This specific interaction stabilizes the structure.

Grooves and Regulatory Proteins

• Major and minor grooves are formed in the DNA structure.
• These grooves provide access for binding of regulatory proteins.
• Anticancer drugs like actinomycin D (dactinomycin) intercalate into the minor groove, inhibiting DNA and RNA synthesis.

Denaturation and Renaturation

• The DNA double-helix can be reversibly melted and re-formed.
• DNA denaturation is the process of separating the two strands, and renaturation is the process of re-forming the double-helix.
• The melting temperature (Tm) depends on the GC content of the DNA.

Mitochondrial DNA

• Mitochondrial DNA is not contained in the nucleus.
• It has a light strand and heavy strand.
• It is maternally inherited and encodes for 22 tRNAs, 2 rRNAs, and 13 proteins involved in the electron transport chain.

Sugar Components

• Ribose is a monosaccharide with 5 carbon atoms (1', 2', 3', 4', and 5').
• 2'-deoxyribose is a sugar component of DNA.
• Ribose is a component of RNA.

Purine and Pyrimidine Bases

• Adenine (A) and guanine (G) are purine bases.
• Cytosine (C) and thymine (T) are pyrimidine bases.

Nucleotides and Nucleosides

• A nucleotide consists of a sugar, phosphate, and nitrogenous base.
• A nucleoside consists of a sugar and a nitrogenous base.

Physiological Functions of Nucleotides

• Nucleotides have various physiological functions in the body.

DNA Polymerization

• A sugar-phosphate chain is stabilized by 3'-5' phosphodiester bonds between 2-deoxyribose residues.

Chargaff's Rule

• The total amount of pyrimidines (T+C) always equals the total amount of purines (A+G).
• The amount of T always equals the amount of A, and the amount of C always equals the amount of G.

Telomere Replication

• Telomerase is an enzyme that helps to maintain telomere length.
• Without telomerase, telomeres may get shorter after each cell division.
• Telomerase has a possible role in 'Aging' and cancer.

This quiz covers the characteristics of Watson and Crick's DNA model, including the structure of the helix, the arrangement of polynucleotide chains, and the properties of purine and pyrimidine bases.