Class 12 Biology - KARNATAKA
Molecular Basis of Inheritance
The chapter Molecular Basis of Inheritance in Class 12 Biology explores the chemical nature of genetic material and how it governs biological traits. Students will study the structure of DNA and RNA, DNA replication, transcription, translation, and gene expression regulation via the lac operon. This chapter also covers the historical milestones like the Hershey-Chase and Meselson-Stahl experiments, and provides an introduction to the Human Genome Project and DNA fingerprinting. It is a high-weightage chapter in Karnataka (KSEEB) board exams, frequently featuring direct theoretical questions, diagrams of transcription and translation units, and numerical problems based on Chargaff's rules.
Start Learning FreeKey Concepts
DNA Structure & Double Helix
DNA is a polynucleotide chain made of deoxyribonucleotides, arranged as a double helix with antiparallel strands held together by hydrogen bonds between complementary nitrogenous bases (A=T, C≡G).
Central Dogma of Molecular Biology
Proposed by Francis Crick, it states that genetic information flows in one direction: from DNA to mRNA via transcription, and from mRNA to proteins via translation.
DNA Replication
The semi-conservative process where DNA makes a copy of itself during the S-phase of the cell cycle, catalyzed primarily by DNA-dependent DNA polymerase in the 5' to 3' direction.
Transcription & Genetic Code
Transcription is the synthesis of RNA from a DNA template. The genetic code is triplet, degenerate, universal, and non-overlapping, translating nucleotide sequences into amino acid chains.
Lac Operon
A classic model of gene regulation in prokaryotes (E. coli) where a cluster of genes is coordinately regulated by a repressor protein and an inducer (lactose).
Important Formulas
Board Exam Info
In the Karnataka (KSEEB) Class 12 Biology board examination, this chapter typically carries around 8 to 12 marks. Questions usually include 1-mark or 2-mark direct definitions, 3-mark conceptual questions (such as differences between DNA and RNA, or steps in DNA fingerprinting), and 5-mark essay questions involving diagrams of the lac operon, Hershey-Chase experiment, or translation process.
Frequently Asked Questions
Why is DNA replication said to be semi-conservative?
Because in each newly formed DNA molecule, one strand is conserved from the parent DNA molecule while the other strand is newly synthesized.
What is the difference between the template strand and the coding strand during transcription?
The template strand runs in the 3' to 5' direction and acts as a template for RNA synthesis, while the coding strand runs in the 5' to 3' direction and has the same sequence as the newly formed mRNA (except Thymine is replaced by Uracil).
What are Okazaki fragments?
Short segments of DNA synthesized discontinuously on the lagging strand (5' to 3' direction) during DNA replication, which are later joined together by the enzyme DNA ligase.
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