Nucleic Acids Lecture Notes
Introduction
- Nucleic acids are essential macromolecules in living systems.
- Include DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
- DNA carries genetic information; some viruses use RNA, but viruses aren't considered living organisms.
Structure of Nucleotides
- Nucleotide Components:
- Pentose sugar (Ribose in RNA, Deoxyribose in DNA)
- Phosphate group
- Nitrogen base
- Model Drawing:
- Sugar is represented by a pentagon.
- Phosphate by a circle.
- Nitrogen base by a rectangle.
DNA Structure
- Composed of nucleotides linked by sugar-phosphate backbone.
- Four nitrogen bases: Adenine (A), Thymine (T), Guanine (G), Cytosine (C).
- Genetic code is the sequence of these bases.
- DNA is double-stranded with strands running in opposite directions (antiparallel).
- Strands are connected by hydrogen bonds between bases:
- A pairs with T
- G pairs with C
RNA Structure
- Single-stranded nucleic acid.
- Uses Uracil (U) instead of Thymine (T).
- Contains ribose sugar.
Differences Between DNA and RNA
- Strands: DNA is double-stranded; RNA is single-stranded.
- Bases: DNA contains A, T, G, C; RNA contains A, U, G, C.
- Sugar: DNA has deoxyribose; RNA has ribose.
Nucleotide Polymerization
- RNA is formed by condensation reactions, similar to DNA.
- Backbone is created by linking nucleotides via phosphate-sugar bonds.
Complementary Base Pairing
- DNA Base Pairing:
- A pairs with T (2 hydrogen bonds)
- G pairs with C (3 hydrogen bonds)
- RNA Base Pairing:
The Significance of DNA
- Stores a large amount of genetic information.
- Base Combinations: Four bases allow for numerous combinations (e.g., 4 bases long can have 256 combinations).
- DNA is compact; fits within cell nuclei.
- The genetic code is universal across living organisms.
- Supports the theory of a universal common ancestor due to shared DNA structure among diverse life forms.
Remember to practice drawing and annotating nucleotide structures and differences between DNA and RNA for exams.