Class 12 Biology - BIHAR
Molecular Basis of Inheritance
The chapter 'Molecular Basis of Inheritance' in Class 12 Biology explores the chemical nature of genetic material and how traits are passed from parents to offspring. It covers the structure and properties of DNA and RNA, the central dogma of molecular biology, DNA replication, transcription, and translation. You will also study gene expression and regulation, the landmark Hershey-Chase and Meselson-Stahl experiments, and the basics of the Human Genome Project and DNA fingerprinting. This is one of the highest-weightage chapters in the Bihar Board (BSEB) examination, frequently featuring long-answer questions and numerical problems related to genetic codes and DNA structure.
Start Learning FreeKey Concepts
DNA Structure
DNA is a double helix composed of two polynucleotide chains running antiparallel, held together by hydrogen bonds between complementary nitrogenous bases (A-T and G-C).
Central Dogma
The unidirectional flow of genetic information states that genetic information flows from DNA to mRNA via transcription, and from mRNA to proteins via translation.
DNA Replication
The semi-conservative process by which a DNA molecule makes an exact copy of itself, assisted by enzymes like DNA polymerase.
Transcription
The synthesis of a complementary RNA strand from a DNA template strand, catalyzed by the enzyme RNA polymerase.
Genetic Code
The set of rules by which information encoded in genetic material is translated into proteins by living cells, consisting of 64 triplet codons.
Lac Operon
An inducible operon in bacteria like E. coli that controls the breakdown of lactose, serving as a classic model for gene regulation.
Important Formulas
Board Exam Info
In the Bihar Board (BSEB) Class 12 Biology exam, this chapter typically carries around 8 to 12 marks. Questions frequently include 5-mark long-answer questions (such as describing the Hershey-Chase experiment, DNA replication, or Lac Operon), multiple-choice questions (MCQs) on the genetic code and enzymes, and 2-mark short notes on transcription or translation.
Frequently Asked Questions
Why is DNA considered a better genetic material than RNA?
DNA is chemically more stable due to the absence of the 2'-OH group on its sugar and the presence of thymine instead of uracil, making it less prone to mutations and degradation compared to RNA.
What is the difference between leading and lagging strands in DNA replication?
The leading strand is synthesized continuously in the 5' to 3' direction, while the lagging strand is synthesized discontinuously in short segments called Okazaki fragments, which are later joined by DNA ligase.
What are the salient features of the genetic code?
The genetic code is triplet, unambiguous, degenerate, universal, comma-less, and non-overlapping, with AUG acting as the start codon and UAA, UAG, UGA as stop codons.
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