Molecular Basis of Inheritance - Lecture Notes

Introduction

• "Molecular Basis of Inheritance" (Foundation of Molecular Signs)
• A short lecture, useful for school exams and NEET
• Listen and understand carefully; all important parts will be covered

Strategy

• Nucleic Acid Structure (DNA and RNA)
• Topic: Information about DNA and RNA
• Essential DNA Structure: Double-stranded and negatively charged
• RNA: Generally single-stranded, double-stranded under some conditions
• Sugar: Deoxyribose in DNA, ribose in RNA
• Nitrogenous Bases: ATGC (DNA), AUGC (RNA)

Genetic Material

• DNA as genetic material in all living cells
• RNA as genetic material in some viruses (e.g., TMV)
• Location of DNA: Nucleus, Mitochondria, Chloroplast
• Location of RNA: Nucleus and Cytoplasm

DNA versus RNA

• DNA: Double-stranded, robust, negatively charged, stable structure
• RNA: Single-stranded, diverse, catalytic role

DNA Structure and Bonding

• Nucleotide: Sugar + Nitrogenous Base + Phosphate Group
• Nucleotides joined by phosphodiester link
• Sugar-Phosphate Backbone, Nitrogenous Bases inward
• Hydrogen Bonding: A = T (two bonds), G ≡ C (three bonds)
• DNA structure formed by complementary strands
• DNA Specification: A right-handed helix, 10 base pairs per turn

Transcription and Translation

• Central Dogma: DNA -> RNA -> Protein
• Transcription: Process of copying DNA, occurs in the nucleus (in eukaryotes)
• Translation: Making protein from RNA, occurs in the cytoplasm
• Transcription Unit: Promoter, Structural Gene, Terminator
• Translation Unit: Three main steps: Initiation, Elongation, Termination
• Mutation: Point Mutation, Substitution Mutation, Deletion Mutation

Genetic Code

• Triplet Code: Three nucleotides code for one amino acid (64 codons, 20 amino acids)
• Properties of the Genetic Code: Universality, Degeneration, No Overlapping
• Start Codon: AUG (Methionine), Stop Codons: UAA, UAG, UGA

Regulation of Gene Expression

• Need for Gene Expression: Development, Metabolic Needs, Environmental Conditions
• Levels of Regulation: Transcription, Modification, Transport, Translation
• Control of Gene Expression: Positive and Negative Regulatory Systems
• Operon Model (Lac Operon): Gene expression by observing lactose in the medium

Human Genome Project

• Start: 1990, Completion: 2003
• Objective: Sequencing and modification of the human genome
• Funding: Nine Billion USD
• Main Agencies: NIH (US), Wellcome Trust (UK), France, Germany
• Methodology: Whole Genome Sequencing, Expressed Sequence Tags (ESTs), Bioinformatics
• Findings: 20,000-25,000 genes, 3 billion base pairs, 1.4 million SNPs

DNA Fingerprinting

• Developed by Alec Jeffreys
• Use: Crime solving, parentage disputes, genetic disorders
• Method: Extraction, Cutting, Electrophoresis, Hybridization, Autoradiography
• Basis: Satellite DNA (Mini and Microsatellites), VNTRs, Method Polymorphism

Summary

• Transcription and translation are important processes
• Operon model explains gene regulation
• Human Genome Project: A major achievement in human genetic mapping
• Importance of DNA Fingerprinting: Crime solving and parentage disputes