Chemical and Molecular Basis of Heredity

• Chromosome is the physical basis of heredity.
• Chromosome is made up of long DNA packed with histones.
• Gene is the molecular basis of heredity.
• Genes are hereditary units.
• Viruses have RNA as their genetic material.
• Uncoiled human DNA has an average lenght of 5 cm.
• Nucleosome is the basic unit of chromatin.
• Nucleosome consists of a protein core of eight histone molecules.

  H2A, H2B, H3, H4
• H1 is associated with linker DNA. They are responsible for chromatin folding.
• DNA and RNA are polynucleotides, they are made up of repeating units of nucleotides.
• The three chemical components of DNA are phosphate group, pentose sugar, and nitrogen base.
• For DNA the sugar is 2-deoxy-D-ribose.
• For RNA the sugar is D-ribose.
• The nitrogen bases can either be purines or pyrimidines.
• Purines have presence of double ring structure.
• Purines are adenine and guanine.
• Pyrimidines are cytosine, thymine, and uracil.
• Pyrimidines are composed of single ring structure known as pyrimidine ring.
• Nitrogen base covalently binds with a sugar to form a nucleoside. The bond called is N-glycosidic bond.
• The nucleoside binds covalently to a phosphate group to form a nucleotide.
• nitrogen base bonds are hydrogen bonds.
• Phosphodiester bond is for sugar and phosphate group.
• DNA are double stranded and anti parallel.
• A pairs with T via two hydrogen bonds.
• G pairs with C via three hydrogen bonds.
• Chemical components of chromosome are nucleic acids, proteins, lipids.
• Nucleic acids are DNA and RNA.
• Friedrick Griffith conducted a study on bacterium D. pneumoniae to mice.
• James D. Watson and Francis Crick proposed the molecular structure of DNA.
• A DNA polymer is consists of nucleotides linked by 3'-5' phosphodiester bonds.
• Chargaff's rule: the ratio of the number of A's to the number of T's is equal to the ratio of the number of C's to the number of G's.
• Specificity of base pairing is one of the most important features as it provides the replicability of genetic material.
• Condensed state of DNA is nucleoid.
• Basic structural unit of eukaryotic chromosome is a nucleosome.
• Three modes of DNA replication: conservative, dispersie, semi-conservative.
• DNA replication is semi-conservative.
• Semi-conservative mode of replication is when each new strand is made from the original parent strand and a new synthesized complementary strand.
• DNA replication/synthesis requires the parental or template DNA as aster copy which the synthesis of daughter DNA molecules.
• Deoxyribonucleotide triphosphates function as substrates.