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Science Class 12 - Genetics And-Evolution Notes

Comprehensive study notes for Class 12 - Genetics And-Evolution olympiad preparation

Genetics and Evolution

Welcome to the chapter on Genetics and Evolution for Class 12. In this chapter, you will learn about the principles of heredity, the structure and function of genes, the process of evolution, and how genetic variation leads to the diversity of life. By the end of this chapter, you will understand the molecular basis of inheritance and the mechanisms driving evolution.

Key Concepts

  • Genetics: The study of heredity and variation in living organisms.
  • Gene: A segment of DNA that codes for a specific protein.
  • Evolution: The process by which different kinds of living organisms develop and diversify from earlier forms.

Mendelian Genetics

Gregor Mendel discovered the basic laws of inheritance by studying pea plants. His laws include:

  • Law of Dominance
  • Law of Segregation
  • Law of Independent Assortment

Mendel's experiments showed that traits are inherited as discrete units called genes.

Molecular Basis of Inheritance

  • DNA: The molecule that carries genetic information.
  • RNA: Helps in protein synthesis.
  • Replication: The process by which DNA makes a copy of itself.
  • Transcription: The process of making RNA from DNA.
  • Translation: The process of making proteins from RNA.

Genetic Code and Mutations

  • Genetic Code: The set of rules by which information in DNA is translated into proteins.
  • Mutation: A change in the DNA sequence that can lead to variation.

Evolution and Natural Selection

Charles Darwin proposed the theory of natural selection, which explains how evolution occurs:

  • Variation exists within populations.
  • Some variations are favorable for survival.
  • Favorable traits are passed on to the next generation.

Over time, this leads to the evolution of new species.

Human Evolution

  • Humans share a common ancestor with other primates.
  • Fossil records and molecular evidence support human evolution.

Applications of Genetics

  • Genetic engineering and biotechnology
  • Gene therapy
  • DNA fingerprinting
  • Conservation of endangered species

Practice Questions

  1. State Mendel's Law of Segregation.
  2. What is the difference between DNA and RNA?
  3. Explain the process of natural selection.
  4. What is a mutation? Give an example.
  5. How does genetic engineering benefit agriculture?

Challenge Yourself

  • Draw a diagram of DNA structure and label its parts.
  • Research and write about one example of evolution in animals or plants.

Did You Know?

  • Humans and chimpanzees share about 98% of their DNA!
  • The fruit fly is often used in genetic experiments because it reproduces quickly.

Glossary

  • Gene: A unit of heredity that is transferred from parent to offspring.
  • Mutation: A change in the DNA sequence.
  • Natural Selection: The process by which organisms better adapted to their environment survive and reproduce.
  • Evolution: The gradual development of different kinds of living organisms from earlier forms.

Answers to Practice Questions

  1. Mendel's Law of Segregation states that allele pairs separate or segregate during gamete formation, and randomly unite at fertilization.
  2. DNA is double-stranded and stores genetic information; RNA is single-stranded and helps in protein synthesis.
  3. Natural selection is the process where organisms with favorable traits survive and reproduce, passing those traits to the next generation.
  4. A mutation is a change in the DNA sequence. Example: Sickle cell anemia is caused by a mutation in the hemoglobin gene.
  5. Genetic engineering can create crops that are resistant to pests, diseases, and harsh environmental conditions, improving yield and quality.

Genetics and evolution explain the diversity of life. Keep exploring to understand the secrets of inheritance and change!

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