Understanding Genetic Crosses: Genotypes, Phenotypes, and Gene Expression through Diagrams, Slides of Biology

Download Understanding Genetic Crosses: Genotypes, Phenotypes, and Gene Expression through Diagrams and more Slides Biology in PDF only on Docsity! Genetic Crosses Show possible outcomes of genes the new generation will have We use: Gene diagrams Punnett Squares Docsity.com Terminology Genotype Phenotype Parent Gamete Offspring dominant recessive allele Docsity.com Genotype and phenotype • Genotype is the letter or term used to describe the allele of an individual gene or pair of genes • Phenotype – is how the gene (or pair) shows itself, how it appears. Docsity.com Dominance and recessiveness • Some alleles for a feature are able to mask the influence of other (weaker) gene when they are paired • Stronger gene is DOMINANT and is represented by a capital letter e.g. H • The masked gene is RESSESIVE shown as lower case of the same letter e.g. h Docsity.com Gene diagram – Flower colour Genotype of alleles- R = red flower r = yellow flower All genes occur in pairs – so 2 alleles affect a characteristic – possible combinations are; genotype RR Rr rr Phenotype RED RED YELLOW Docsity.com Gene diagram – Flower colour Male female Rr rr parent gamete R r r r Offspring genotype Rr Rr rr rr Phenotype Red yellow yellow red Red 50% yellow 50% Docsity.com Punnett Square • Another method of showing crosses Docsity.com Gamete genotypes are inserted Parent genotypes are inserted B=black b=white Bb male black bb white female B b b b What are the crosses Bb bb Bb bb 2 white and 2 black offspring 50:50 chance with these parents Docsity.com