10.2 Mendelian Genetics Genetics – The science of heredity. Mendel – Father of genetics

The Inheritance of Traits Cross green-seed plant with a yellow-seed plant – Parent (P) generation F1and F2 generations First Filial (F1) generation – All yellow Self fertilization Second Filial (F2) generation – 6022 yellow and 2001 green (a 3:1 ratio)

The Inheritance of Traits

Genes in Pairs Allele – Alternative form of a single gene passed from generation to generation. Represented by a single letter (Y) Dominant and recessive (3:1)

Dominance Dominant gene – the allele that overpowers other alleles Represented by a capital letter (Y) Recessive gene – the allele that is hidden by the dominant allele Represented by a lowercase letter (y)

Dominance Homozygous Heterozygous An organism with two of the same alleles for a particular trait. Example: YY (yellow) or yy (green) An organism with two different alleles for a particular trait Example: Yy (yellow)

Genotype and Phenotype The organism’s allele pairs. Example: Yy or YY or yy The observable characteristic or outward expression of an allele pair. Example: yellow or green

Mendel’s Law of Segregation States that the two alleles for each trait separate during meiosis. Hybrids – Genotype Yy and has yellow seeds.

Law of Independent Assortment States that a random distribution of alleles occurs during gamete formation.

Punnett Squares Developed by Dr. Punnett in the early 1900s to predict possible offspring between two known genotypes.

Punnett Squares Alleles for all possible male gametes go on the top two columns. Alleles for all possible female gametes go on the left rows. The boxes are filled in with the corresponding allele.

Monohybrid Cross A cross that involves hybrids for a single trait. Genotypic ratio is 1:2:1 Phenotypic ratio is 3:1

Monohybrid Cross

Dihybrid Cross A cross between two heterozygous organisms for two traits.

Dihybrid Cross (F2 Generation)