Bellwork: 4/9 Put your phone up  Week 4/8 - 4/12 Create your own punnett square problem & solve it

Today: Bellwork Part 3 Notes Dihybrid Practice

Materials Unit Book Dihybrid Practice Worksheet

This Week: Monday: PS Quiz & Assign Project Tues/Wed: Pt. 3 Notes & Practice Thursday: Dihybrid Practice & Pt. 4 Notes Friday: Blood Type Practice & Pt. 5 Notes

Homework Dihybrid Practice Genetic Illness Sign-Up Genetics Project Due Thursday Genetic Illness Sign-Up Due Friday 4/12 Genetics Project Due 4/24 at 11:59pm

Unit VI: Mendelian Genetics

Part III: Dihybrid Crosses

Review ?s What was Mendel’s first law of inheritance? How is his first law related to meiosis?

Monohybrid Crosses Involves the transmission of a single trait

Next ? Mendel Asked Would the possession of one particular trait (e.g. seed shape) influence the segregation of another trait (e.g. seed color) or would they segregate independently?

Dihybrid Crosses Mendel examined simultaneous inheritance of two traits The 2 traits he examined… Seed Shape – Round (R, dominant) versus wrinkled (r, recessive) Seed Color – Yellow (Y, dominant) versus green (y, recessive)

THINK! What distinguishes a monohybrid cross from a dihybrid cross?

Developed 2 Hypotheses Hypothesis 1: Two traits segregate together Hypothesis 2: Two traits segregate independently

Hypothesis 1 Round (R) always goes with yellow (Y) Wrinkled (r) always goes with green (y) Predicted results from Punnett Square 3 round yellow:1 wrinkled green

Hypothesis 1I Based on this hypothesis there are 4 possible gamete combinations RY, Ry, rY, ry Cross RrYy X RrYy Predicted Results: 9 Round, Yellow: 3 wrinkled, Yellow: 3 Round, green: 1 wrinkled, green

Punnett Square

2nd Law of Inheritance Law of Independent Assortment Why Each allele pair on non-homologous chromosomes segregates independently of other gene pairs during gamete formation Why Because non-homologous chromosomes line up randomly in the center of the cell & are pulled to different poles How they assort determines the homologous chromosomes (maternal vs paternal) the gamete possesses.

THINK! Explain the difference between homologous & non-homologous chromosomes.

Solving Dihybrid PS Dihybrid Crosses Determine genotype of parents Determine possible gamete combinations for each parent determined by the equation 2n where n = number of heterozygotes If n = 0, RRyy, then 2o = 1, only one possible gamete combination Ry If n=1, Rryy, then 21 = 2, two possible gamete combination Ry, ry If n=2, RrYy then 22= 4, four possible gamete combinations RY, Ry, rY, ry Set up Punnett square Fill in squares by combining allele from sperm and egg Answer the question

Sample Problem! In tomatoes, red fruit (R) is dominant over yellow fruit (r) and tallness (T) is dominant over shortness (t). A plant that is RrTT is crossed with a plant that is rrTt. What are the chances of an offspring being heterozygous for both traits?