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Molecular Genetics

Tamil Nadu Board · Class 12 · Zoology

Quick revision notes for Molecular Genetics — Tamil Nadu Board Class 12 Zoology. Key concepts, formulas, and definitions for last-minute revision.

45 questions25 flashcards5 concepts

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An infographic summarizing the key characteristics of the genetic code: triplet, degenerate, unambiguous, universal, non-overlapping, and commaless, with brief explanations or examples for each proper
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Key Topics to Revise

1

5.1 Gene as the Functional Unit of Inheritance

  • A gene is the basic physical and functional unit of heredity carrying discrete hereditary information
  • Gregor Mendel (1860s) discovered genes but called them 'factors'; Wilhelm Johannsen coined the term 'gene' in 1909
  • Genes occupy specific positions (loci) on chromosomes and exist in alternate forms called alleles
2

5.2-5.3 Search for Genetic Material and DNA as Genetic Material

  • Friedrich Miescher (1869) isolated 'nuclein' from cell nuclei; renamed as nucleic acid by Altman (1889), now known as DNA
  • Griffith's transformation experiment (mentioned in class XI) showed unknown substance could transform bacteria
  • Avery, Macleod, and McCarty (1944) identified DNA as the transforming principle using in vitro experiments
3

5.4 Chemistry of Nucleic Acids

  • Nucleic acids are polymers of nucleotides, each composed of pentose sugar + nitrogenous base + phosphate group
  • DNA contains deoxyribose sugar; RNA contains ribose sugar - difference is one less oxygen in deoxyribose
  • Purines (A, G): double-ring structures; Pyrimidines (C, T, U): single-ring structures
4

5.5 RNA World

  • A typical cell contains about 10 times as much RNA as DNA
  • Fraenkel-Conrat and Singer (1957) demonstrated RNA as genetic material in TMV and other RNA viruses
  • 'RNA world' hypothesis proposed by Orgel, Crick, and Woese (early 1980s) suggests RNA was first genetic material on Earth

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Full Notes

Key Concepts

A gene is a discrete segmentMultiple experiments established DNA asDNA and RNA are polymers madeWatson and Crick (1953) proposedThe RNA world hypothesis proposes

Frequently Asked Questions

What are the important topics in Molecular Genetics for Tamil Nadu Board Class 12 Zoology?
Key topics in Molecular Genetics include Molecular Genetics - Complete Concept Overview, Mind map showing the gene concept, its properties, and related hypotheses, Flowchart showing progression of key experiments that identified DNA as genetic material. These are the concepts Tamil Nadu Board Class 12 examiners draw on most — study them first, then practise related questions.
How to score full marks in Molecular Genetics — Tamil Nadu Board Class 12 Zoology?
Understand the core concepts first, then work through the 45 practice questions available for this chapter. Revise formulas and definitions regularly, and use flashcards for quick recall before the exam.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

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