DNA as Genetic Material:
Established through experiments by Griffith, Avery, MacLeod & McCarty, and Hershey & Chase.
DNA is a long polymer with a deoxyribose (pentose) sugar, phosphate group, and nitrogenous bases (Adenine, Thymine, Cytosine, Guanine).
Structure of DNA:
Double helix model proposed by Watson and Crick.
Antiparallel strands held together by hydrogen bonds between complementary base pairs (A-T and G-C).
Replication of DNA:
Semi-conservative replication model.
DNA helicase unwinds the helix, DNA polymerase facilitates the addition of new nucleotides.
RNA World:
RNA believed to be the first genetic material.
Types of RNA: mRNA (Messenger), tRNA (Transfer), rRNA (Ribosomal).
Transcription:
Process of synthesizing RNA from DNA template.
In eukaryotes, primary transcript (hnRNA) undergoes splicing, capping, and tailing to form mature mRNA.
Genetic Code:
Triplet code, codon specific to amino acids.
64 possible codons, 61 code for amino acids, and 3 are stop codons.
Universal in nature with few exceptions.
Translation:
Process of protein synthesis from mRNA template.
tRNA acts as an adapter, carrying specific amino acids to ribosomes where polypeptide synthesis occurs.
Regulation of Gene Expression:
Not all genes are active at all times.
In prokaryotes: Operon model (e.g., Lac operon).
In eukaryotes: Multiple levels of regulation (chromatin level, transcriptional, post-transcriptional, translational, and post-translational).
Human Genome Project:
Aims to sequence the entire human genome and identify all genes.
Outcomes: Identified ~20,500 protein-coding genes; understanding of molecular basis of diseases; drug design.
DNA Fingerprinting:
Technique to identify individuals based on DNA patterns.
Uses Short Tandem Repeats (STRs) for identification.
Applications: Forensics, paternity testing, biodiversity studies.