Genetic Crosses

Genotype/Phenotype Genotype Phenotype Genetic make-up of an organism Example= TT, Tt, tt Phenotype Appearance of an organism Example= Tall or short, Red hair or black hair

Probability Probability Likelihood that a specific event will occur May be expressed as a decimal, fraction, or percentage Example: Dice probability lab

Alleles For each trait, there is a dominant and a recessive allele. The dominant trait is represented by a capital letter and recessive by a lower case letter Alleles can be represented by any letter. Capitalization is all that matters. Three possible genotypes in organisms: AA=homozygous dominant Aa=heterozygous aa=homozygous recessive

Allelic Frequencies Homozygous Heterozygous Describes an individual that has identical alleles for a trait on both homologous chromosomes Homozygous dominant=TT Homozygous recessive=tt Heterozygous Describes an individual that has two different alleles for a trait Example= Tt

Monohybrid Crosses Monohybrid Cross Punnett Square Test Cross Cross between individuals that involves one pair of contrasting traits Punnett Square Technique that can be used to predict the outcome of genetic crosses Test Cross An individual with an unknown genotype is crossed with a homozygous recessive individual

Punnett Square Crosses

Dominance Complete Dominance Incomplete Dominance Codominance Occurs when heterozygous individuals and dominant homozygous individuals are impossible to tell apart in phenotype Incomplete Dominance Occurs when two or more alleles influence the phenotype and results in a phenotype intermediate between the dominant trait and the recessive trait Codominance Occurs when both alleles for a gene are expressed in a heterozygous offspring

Dihybrid Cross Dihybrid Cross Cross in which two characteristic traits are tracked