If you have a dominant phenotype (like purple flowers) how would you determine if it was homozygous (PP) or heterozygous (Pp)? What experiment would you design? Dominate alleles mask recessive ones Dominant phenotype, unknown genotype: PP or Pp? Recessive phenotype, known genotype: pp What would your hypothesis be if the genotype was PP? What would your hypothesis be if the genotype was Pp? If PP, then all offspring purple: If Pp, then ½ offspring purple and ½ offspring white: P p P p Pp Pp P p p p Pp Pp pp Pp Pp pp This is called a test cross Back to Mendel’s Conclusions

Review: Law of Segregation Two alleles for each trait segregate (______________) during gamete production separate In what way does crossing over segregate alleles? In what way does Meiosis I and Meiosis II segregate alleles?

Page 295 Discuss: Observe the images below. Explain to your group or seat partner the difference between linked genes and genes that are not linked. Use the image below to help you.

Law of Independent Assortment: Page 296 Law of Independent Assortment: Two different genes can separate independently from one another if they are on separate chromosomes and are not linked. The law of segregation followed one single trait at a time, such as seed color. What if two traits were followed, such as seed color and seed shape? Are the genes for seed color and seed shape always inherited together? In other words, are yellow seeds always round and green seeds always wrinkled? To help you find out, answer questions 1-4 on page 296.

Page 296 Alleles for Seed Color: Yellow (Y) or green (y) Alleles for Seed Texture: Round (R) or wrinkled (r)

Back to “Beyond Mendel” Linked Genes Genes that are linked, and found on the same chromosome will most likely be inherited together and will not undergo Mendel’s Law of unless cross over segregates the linked genes independent assortment g g G G W w W w Back to “Beyond Mendel”

Circle which stages of Meiosis Creates the Law of Independent Assortment

YyRr YyRr x YyRr Law of Independent Assortment What are the genotypes of the P Generation? YYRR yyrr Law of Independent Assortment What does the P Generation pass on to F1? YR yr Gametes F1 Phenotype? YyRr YyRr x YyRr F1 Genotype? What does the F1 Generation pass on to F2? Ova Sperm YR YR Yr Combine the sperm and ova to produce the offspring in F2 Yr YYRR yR yR YYRr YYRr yr yr What do you expect the phenotype will be when YR and YR are combined? YyRR YYrr YyRR Phenotypic Ratios YyRr YyRr YyRr YyRr 9/16 Yellow & Round What will the Genotype be when YR and YR are combined? Yyrr yyRR Yyrr 3/16 Green & Round yyRr yyRr 3/16 Yellow & Wrinkled yyrr 1/16 Green & Wrinkled

Page 298 How do I use statistics and probability to predict genotypic and phenotypic ratios?

White-board exercises Two-trait cross Following two traits: Kernel shape: Plump vs. withered (P and p) and Kernel color Red vs. yellow (R and r) Predict the cross between a homozygous recessive corn plant and a homozygous dominant corn plant.

Punnett Square Exercise Two-trait cross Now take the offspring from that cross, and self-pollinate that plant. What is the phenotypic ratio of this cross?

Punnett Square Exercise Two-trait cross My pet guinea pigs (Joni and Chachi) are going to have little guinea pigs. What is the possibility that their offspring will have long hair, if I know that Joni and Chachi are heterozygous for the following traits? Black fur (B) White fur (b) Long hair (L) Short hair (l)