Introduction to Inheritance

Introduction to InheritanceBiologyEssential QuestionHow are the traits of one generation passed on to the next?

Objective: We will predict possible outcomes of monohybrid crosses.How Genetics BeganThe passing of traits to the next generation is called inheritance, or heredity.Gregor Mendel is known as the father of genetics.Mendel performed cross-pollination in pea plants.Mendel followed various traits in the pea plants he bred.Seed or pea colorFlower colorSeed pod colorSeed shape or textureSeed pod shapeStem lengthFlower positionParents and OffspringThe parent generation is also known as the P generationThe offspring of this P cross are called the first filial (F1) generation.The second filial (F2) generation is the offspring from the F1 cross.

Genes in PairsAn alternative form of a single gene passed from generation to generation is an allele.Mendel called the form of the trait that appeared in the F1 generation dominant.Mendel called the form of the trait that was masked in the F1 generation recessive.

DominanceAn organism with two of the same alleles for a particular trait is homozygous. Example: GG or ggAn organism with two different alleles for a particular trait is heterozygous. Example: Gg

Genotype and PhenotypeAn organisms allele pairs are called its genotype.Remember: Genes are in the genotype!The observable characteristic or outward expression of an allele pair is called the phenotype. Remember: Phenotype is what you see!

Mendels Law of SegregationTwo alleles for each trait separate during meiosisDuring fertilization, two alleles for that trait unite.Heterozygous organisms are called hybrids.Homozygous organims are called purebreds.

Law of Independent AssortmentRandom distribution of alleles occurs during gamete formationGenes on separate chromosomes sort independentlyHappens during Anaphase II in meiosisEach allele combination is equally likely to occur.

Monohybrid Crosses and Punnett SquaresA cross that involves hybrids for a single trait is called a monohybrid cross.Punnett Squares are used to predict the possible offspring of a cross between two known genotypes.

Crosses

Father- Brown EyesBBMother- Blue EyesbbGenotypic ratio0:1:0Phenotypic ratio1:0Father- Brown (BB)Mother- Blue (bb)BBbbBbBbBbBbBrownBrownBrownBrownCrosses

Father- Brown EyesBbMother- Blue EyesbbGenotypic ratio0:1:1Phenotypic ratio1:1Father- Brown (Bb)Mother- Blue (bb)bBbbBbbbBbbbBlueBrownBlueBrownCrosses

Father- Brown EyesBbMother- Brown EyesBbGenotypic ratio1:2:1Phenotypic ratio3:1Father- Brown (Bb)Mother- Brown (Bb)bBBbBBBbBbbbBlueBrownBrownBrownRememberThese are Cornell notes, so3 questions in the left hand columnHonors- 2 must be Costas level 2 or 3Regulars- 1 must be Costas level 2 or 3Summary at the bottom of the pageBaby Traits