Two Trait Crosses The Dihybrid Cross What is

Two Trait Crosses: The Dihybrid Cross

What is a Dihybrid Cross? Determines the probability of genetic outcomes for TWO traits instead of ONE.

How are Dihybrid Crosses Possible? Law of Independent Assortment, different traits are not linked and have equal probability of showing up in offspring. Example: Tall Purple plants, Tall White plant, short purple plants and short white plants.

Mendel’s Laws of Heredity Law of independent assortment: each pair of alleles segregates into gametes independently 4 sets of gametes are produced in equal probability YR, Yr, y. R, yr

How to’s of Dihybrid Crosses • 1. Figure out the alleles: • 2. Draw your box (16 squares for dihybrids!) • 3. Determine the Possible gametes (sex cells) that could be made from the parents. • 4. Label each side of Box, • 5. Determine your possible Genotypes! • 6. Determine your possible Phenotypes!

Practice • What are the chances of getting a Tall Green Plant when a Tall Green and a Tall Yellow Pea pant are crossed. • (Tt. GG x Ttgg)

Dihybrid cross P true-breeding yellow, round peas Y = yellow R = round generation (hybrids) F 2 generation YYRR yyrr yellow, round peas F 1 self-pollinate x true-breeding green, wrinkled peas y = green r = wrinkled All HYBRIDS! 100% Yy. Rr Dominant/ Dominant 9/16 yellow round peas Recessive /Dominant/ Recessive/ Recessive 3/16 green round peas 3/16 yellow wrinkled peas 1/16 green wrinkled peas Mendel’s Magic Ratio of Hybrids! 9: 3: 3: 1

Your Turn! Dihybrid cross of color and seed shape Yy. Rr x Yy. Rr YR Yr y. R yr YR YYRr Yy. RR Yy. Rr Yr YYRr YYrr Yy. Rr Yyrr y. R Yy. Rr yy. RR yy. Rr yr Yy. Rr Yyrr yy. Rr yyrr 9/16 yellow round 3/16 green round 3/16 yellow wrinkled 1/16 green wrinkled