Mendelian Genetics Basics Fernando

Genetics basics Mendelian activity

Parent Generation Cross pollination

Parent Generation F1 Generation

Parent Generation F1 Generation Self pollination

Parent Generation F1 Generation ?

Parent Generation F1 Generation F2 Generation, 3:1 ratio

Parent Generation F1 Generation F2 Generation, 3:1 ratio Why?

Mendelian vocabulary Hereditary factors Hybrid Pure or purebreed

Dihybrid Cross Traits : Seed shape & Seed color Alleles : R round / r wrinkled Y yellow / y green RrYy x RrYy

RrYy x RrYy RY Ry rY ry RY Ry rY ry All possible gamete combinations

Genetic Terminology Trait - any characteristic that can be passed from parent to offspring Heredity - passing of traits from parent to offspring Genetics - study of heredity

Types of Genetic Crosses Monohybrid cross - cross involving a single trait e.g. flower color Dihybrid cross - cross involving two traits e.g. flower color & plant height

Alleles - two forms of a gene (dominant & recessive) Dominant - stronger of two genes expressed in the hybrid; represented by a capital letter (R) Recessive - gene that shows up less often in a cross; represented by a lowercase letter (r) Terminology

Genotype - gene combination for a trait (e.g. RR, Rr, rr) Phenotype - the physical feature resulting from a genotype (e.g. red, white) Terminology

Genotypes Homozygous genotype – When the two alleles are same (dominant or 2 recessive genes ) e.g. TT or tt; also called pure Heterozygous genotype – When the 2 alleles are different- one dominant & one recessive allele ( e.g. Tt); also called hybrid

Mendel’s Laws 1. Law of Dominance 2. Law of Segregation 3. Law of Independent assortment

Law of Dominance States that on crossing homozygous organisms for single pair of contrasting characters, only one characters make its appearance in F 1 generation and is name as Dominant character . 1

Law of Segregation During the formation of gametes (eggs or sperm), the two alleles responsible for a trait separate from each other. Alleles for a trait are then "recombined" at fertilization, producing the genotype for the traits of the offspring . 2

Law of Independent Assortment Alleles for different traits are distributed to sex cells (& offspring) independently of one another. This law can be illustrated using dihybrid crosses . 3

Mendel’s Experimental Methods Mendel hand-pollinated flowers using a paintbrush He could snip (cut) the stamens to prevent self-pollination He traced traits through the several generations

Why peas, Pisum sativum ? Can be grown in a small area Produce lots of offspring Produce pure plants when allowed to self-pollinate several generations Can be artificially cross-pollinated Bisexual. Many traits known . Above all, easy to grow

Some slides were taken from a previous work by Dr. R. Siva (VIT University, INDIA)

Mendelian Genetics Basics Fernando

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