Genetics-And-Evolution-Principles-Of-Inheritance-And-Variation-1

Mendel’s Pea Plant Experiments:

Gregor Mendel conducted experiments with pea plants in the 19^th century.

Chose pea plants due to distinct traits and easy cross-breeding.

Studied seven traits, each with two variants (e.g., flower color: purple and white).

Principles of Mendel’s Experiments:

Used controlled cross-fertilization.

Labeled generations as P (parental), F₁ (first filial), and F₂ (second filial).

Discovered Law of Segregation (allele separation) and Law of Independent Assortment (independent gene segregation).

Observed phenotypic ratios in F₂ generations (e.g., 3:1 for monohybrid cross).

Phenotype:

Observable traits in organisms.

Mendel studied traits like flower color, seed color, and more.

Identified dominant (expressed) and recessive (masked) traits.

Monohybrid Cross:

Cross involving one specific trait.

Starts with purebred parental plants.

Produces F₁ generation with all heterozygous individuals.

F₂ generation exhibits 3:1 phenotypic ratio (e.g., 3 purple: 1 white).

Self-Pollination in F1 Plants:

F₁ generation results from cross-breeding.

F₁ plants are heterozygous for the trait.

Self-pollination of F₁ plants results in F₂ generation.

F₂ generation exhibits phenotypic ratio based on dominant and recessive alleles.

Hybridization of Parents:

Hybridization involves breeding different individuals to create hybrids.

Examples in plants, animals (e.g., mule, liger), bacteria, and fish.

Used for desirable traits and improvements.

Phenotypic and Genotypic Ratio:

Phenotypic ratio is the proportion of observable traits.

Genotypic ratio is the proportion of genetic combinations.

Ratios depend on alleles and traits.

Monohybrid cross often results in 3:1 phenotypic ratio and 1:2:1 genotypic ratio.