2 Making Genetic Predictions Mendel found that you could predict thetraits of a percentage of the offspring.He invented and used the tool of a Punnettsquare to illustrate these percentages.
3 Punnett Squares The Law of Dominance Traits are shown with a Capital letter fordominant and a lower case for recessive– Brown Eyes (B) Blue Eyes (b)
4 Punnett Squares Eye Color – Brown eyes B – Blue eyes b Purebred individual with brown eyes (BB)– HomozygousPurebred individual with blue eyes (bb)Hybrid individual with brown eyes (Bb)– Heterozygous
5 Punnett Squares Eye Color – Father is (BB) – Mother is (bb) Their Genes Are Crossed– BB x bb– Since we are looking at only 1 gene, it is called a monohybrid cross.
6 Law Of Segregation Law of Segregation – Alleles for the same trait must be in separate sex cells.– Father is (BB) as his diploid genotype– Mother is (bb) as her diploid genotypeSomatic Cells BB bbSex cells B B b b
7 Monohybrid Crosses Monohybrid cross deals with one gene – We are working with only eye colorSetting up a punnet squareThe sex cells go on theoutside of the square
8 Punnett Squares b B B Bb = Brown All of the offspring will have brown eyes,but they will beheterozygousindividuals.b
9 Punnett Squares Eye Color – Father has Brown eyes and is heterozygous (Bb).– Mother has Brown eyes and is heterozygous (Bb).
14 Ratios Genotype Ratio – 0 BB to 2 Bb to 2 bb (reduce) Phenotype Ratio– 2 Brown eyes to 2 blue eyes (reduce)– 1 Brown eye to 1 blue eyeWhat is the chance of this couple having a child with blue eyes?– ½ or 50%
15 Mendel’s WorkPea Color:Yellow: YGreen: yP GenerationYY x yy
16 Mendel’s Work Crossed two of the F1 to see what the F2 would look like.
17 Multiple Characteristics Punnett Squares work with multiple characteristics.Crosses can be done with an assortment of genes.
18 Dihybrid CrossesThe Parents are heterozygous for both hair and eye color (BbEe: Brown hair and Brown Eyes).– B: Brown hair - E: Brown eyes– b: Blonde hair - e : Blue eyesCross = BbEe x BbEe
19 Mendel’s Laws The law of segregation – You can’t have the same letters in a Sex cellThe law of independent assortment– The two genes will have their alleles placed into the same sex cells randomly.Work with one parent at a time– BbEe (B b) (E e)– Possible sex cells– (BE) (Be) (bE) (be)