Biology Masterclass: The Logic of Life's Code

Phase 1: Molecular Genetics (The Hard Drive)

Genetics is the study of how information is stored, replicated, and expressed in living organisms.

1. The Central Dogma

Information flow in a cell: DNA $\xrightarrow{Transcription}$ RNA $\xrightarrow{Translation}$ Protein.

• Replication: DNA making a copy of itself (S-phase of cell cycle).
• Transcription: DNA rewritten as RNA (happens in Nucleus).
• Translation: RNA code used to build Proteins (happens in Ribosomes).

2. DNA vs RNA (Technical Differences)

Phase 2: Mendelian & Chromosomal Inheritance

1. Genetic Terms to Master

• Alleles: Alternative forms of a gene (e.g., T and t).
• Phenotype: Observable traits (e.g., Purple flowers).
• Genotype: Genetic makeup (e.g., Pp).
• Mutation: A sudden heritage change in DNA sequence. (Can be beneficial, neutral, or harmful).

2. Chromosomal Syndromes (Ranker's List)

Phase 3: Biotechnology & Modern Genetics

1. Advanced Tools

• PCR (Polymerase Chain Reaction): Used to make billions of copies of a small DNA sample. (The "Xerox machine" for DNA).
• CRISPR-Cas9: The "Molecular Scissors" used to edit DNA precisely.
• DNA Fingerprinting: Alec Jeffreys (World), Lalji Singh (India). Used for solving crimes/paternity.

Phase 4: The Exam Edge (High-Yield Facts)

• Autosomes: 22 pairs (same for M/F). Sex Chromosomes: 1 pair (Different).
• Hemophilia: "Royal Disease". X-linked recessive disorder where blood doesn't clot properly.
• Color Blindness: Red-Green deficiency. More common in males.
• Father of Indian Genetics: Dr. M. S. Swaminathan (Agricultural focus).

[!IMPORTANT]
The Gender Logic: $X$ Sperm + $X$ Egg = Girl ($XX$). $Y$ Sperm + $X$ Egg = Boy ($XY$). Sex of the baby is always determined by the father.