Class 12 Biology - CBSE
Molecular Basis of Inheritance
The chapter 'Molecular Basis of Inheritance' explores DNA and RNA as the genetic material responsible for storing and transferring hereditary information. You will learn about the structure of DNA, the famous Watson and Crick model, DNA replication, transcription, translation, and the monumental Human Genome Project. This chapter forms the core of modern genetics and is heavily weighted in the CBSE Class 12 Biology board exam. Questions often test your conceptual clarity on replication forks, the central dogma, lac operon regulation, and experimental proofs like Hershey-Chase and Meselson-Stahl, making it crucial for scoring high.
Start Learning FreeKey Concepts
Central Dogma of Molecular Biology
Proposed by Francis Crick, it dictates the unidirectional flow of genetic information from DNA to RNA via transcription, and from RNA to protein via translation.
DNA Replication
The semi-conservative process where DNA makes a copy of itself using DNA polymerase enzyme, moving in the 5' to 3' direction with leading and lagging strands.
Transcription
The process of copying genetic information from one strand of DNA into RNA by RNA polymerase, involving promoter, structural gene, and terminator regions.
Genetic Code
The dictionary of nucleotide triplets (codons) that dictates amino acid sequences in proteins, characterized by being degenerate, universal, and non-overlapping.
Lac Operon
An inducible gene regulation system in bacteria like E. coli consisting of a regulatory gene, operator, and structural genes that metabolize lactose when present.
DNA Fingerprinting
A technique identifying individuals based on VNTR (Variable Number of Tandem Repeats) polymorphism, widely used in forensic science and paternity testing.
Important Formulas
Board Exam Info
In the CBSE Class 12 Biology board examination, this chapter typically carries around 6 to 8 marks. Common question types include 2-mark reasoning questions on DNA replication enzymes, 3-mark diagram-based questions on transcription units or lac operon, and 5-mark long-answer questions explaining experiments like Hershey-Chase or the mechanism of translation.
Frequently Asked Questions
Why is DNA replication semi-conservative?
During replication, each of the two resulting DNA molecules receives one strand from the parental duplex and one newly synthesized strand, conserving half of the original DNA.
What is the difference between the leading strand and lagging strand?
The leading strand is synthesized continuously in the 5' to 3' direction towards the replication fork, while the lagging strand is synthesized discontinuously in short segments called Okazaki fragments.
What is the role of histones in DNA packaging?
Histones are positively charged proteins rich in basic amino acids that bind to negatively charged DNA to form repeating units called nucleosomes, allowing long DNA molecules to fit inside the nucleus.
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