Bb B b 1. Using the picture above, explain Mendel’s Law of Segregation. 2. Why is this Punnett square set up incorrectly? Ts t S 3. Why is this Punnett square set up incorrectly? TT Tt

Section 10.1 Summary – pages Remember, Mendel performed experiments on pea plants that only differed in one trait: HEIGHT Di-hybrid crosses Mendel then decided to perform another set of crosses in which he used peas that differed from each other only in TWO traits rather than one.

Di-hybrid crosses These experiments were called Di-hybrid crosses: Di means “two” - because there were only two differences Hybrid because the parents were different from each other (in two ways) Cross because he chose the parents to breed with each other The pea plants were the same in every way, EXCEPT PEA SHAPE (round, wrinkled) and PEA COLOR (yellow, green)

Section 10.1 Summary – pages Mendel took pure-bred plants with round yellow peas and crossed them with pure-bred plants with wrinkled green seeds. In pea plants: Round is Dominant “R” and Wrinkled is Recessive “r” Yellow is Dominant “Y” and Green is Recessive “y” THE TWO DIFFERENCES RR YYrr yy

Section 10.1 Summary – pages What happened with the first generation of offspring? What happened with the second generation of offspring? P1- Parents F1- first generation of offspring F2- 2 nd generation of offspring

Section 10.1 Summary – pages The Law of Independent Assortment states: genes for different traits—(for example, eye shape and eye color)— are inherited independently of each other. The Law of Independent Assortment Bb bb rrRR Bb Rr

Section 10.1 Summary – pages A Punnett square for a dihybrid cross will need to be four boxes on each side for a total of 16 boxes. Dihybrid crosses Punnett Square of Dihybrid Cross Gametes from RrYy parent RYRyrYry Gametes from RrYy parent RY Ry rY ry RRYY RRYy RrYYRrYy RRYy RrYy Rryy RrYYRrYyrrYY rrYy RrYy Rryy rrYy rryy

Section 10.1 Summary – pages Remember with the Law of Segregation in a mono-hybrid cross, you had to separate the alleles because you can only pass ONE ALLELE FOR EACH TRAIT on to your offspring. TTTt tt Tt T t In a di-hybrid, you still only pass one allele PER trait to your offspring…. RR YY But remember: in a di-hybrid you have two traits…. R Y

Let’s practice one together, then you will do one on your own. Male parent is Heterozygous for Brown eyes and Homozygous recessive for almond eyes: Female parent is Homozygous recessive for Blue eyes and Heterozygous for Round eyes: Bb rr bb Rr B r b r b R b r Bb Rrbb RrBb Rrbb Rr Bb rrbb rrBb rrbb rr Bb Rrbb RrBb Rrbb Rr Bb rr bb rr Bb rr

Head, C-curly, c-straight Eyes, S-slanted, s-straight Father, CcSs (Curly hair, Slanted eyes) Mother, CcSs (Curly hair, Slanted eyes) CSCscScs CS Cs cS cs CCSSCCSs CcSSCcSs CCSsCCssCcSs Ccss CcSS CcSs ccSSccSs CcSsCcssccSsccss