Genetics | Lucent for GK - UPSC PDF Download

Introduction

• Genetics is the branch of biology that deals with the study of heredity, variation, and the characteristics of organisms.
• Gregor Mendel is considered the father of genetics for his pioneering work on pea plants in the mid-19th century.
• Genes are the basic units of heredity, composed of DNA, which carries the instructions for building and maintaining an organism.
• Chromosomes are thread-like structures found in the nucleus of cells that contain the genetic information.
• Genotype refers to the genetic makeup of an individual, while phenotype refers to the physical expression of the genotype.

Monohybrid Cross

• A monohybrid cross is a breeding experiment that involves the study of one trait or characteristic.
• Mendel's experiments with pea plants focused on monohybrid crosses, where he studied traits such as seed color (yellow or green) and flower color (purple or white).
• Mendel formulated the law of segregation, which states that each individual possesses two alleles for a trait, and these alleles segregate during gamete formation, with only one allele passing to each offspring.

Dihybrid Cross

• A dihybrid cross is a breeding experiment that involves the study of two traits simultaneously.
• Mendel's experiments also included dihybrid crosses, where he studied traits such as seed color and seed shape.
• Mendel formulated the law of independent assortment, which states that during gamete formation, the segregation of alleles for one trait is independent of the segregation of alleles for another trait.

Laws of Genetics

• Law of Segregation: Each individual possesses two alleles for a trait, which segregate during gamete formation, with only one allele passing to each offspring.
• Law of Independent Assortment: The segregation of alleles for one trait is independent of the segregation of alleles for another trait during gamete formation.

Terms Related to Genetics

• Allele: Different forms or variants of a gene.
• Homozygous: When an individual carries two identical alleles for a particular trait (e.g., AA or aa).
• Heterozygous: When an individual carries two different alleles for a particular trait (e.g., Aa).
• Dominant: An allele that is expressed phenotypically and masks the effect of the recessive allele.
• Recessive: An allele that is expressed phenotypically only in the absence of a dominant allele.
• Punnett Square: A diagrammatic representation used to predict the possible genotypes and phenotypes of offspring in a genetic cross.
• Genetic Mutation: A permanent alteration in the DNA sequence of a gene, which can result in a change in the phenotype.
• Genetically Modified Organisms (GMOs): Organisms whose genetic material has been altered through genetic engineering techniques.