This biology question covers important biological concepts and processes. The step-by-step explanation below helps you understand the underlying mechanisms and reasoning.
ScanSolve AI Answer
Let's break down this Dihybrid cross. First, we define the alleles for the two traits: For seed shape: R* = Round (dominant allele) r* = wrinkled (recessive allele) For seed color: Y* = Yellow (dominant allele) y* = green (recessive allele) We are crossing a plant with round and yellow seeds with a plant with wrinkled and green seeds. Assuming these are pure-breeding (homozygous) parents, their genotypes will be: Round and Yellow parent: RRYY* wrinkled and green parent: rryy* Step 1: Parental (P) Generation Parent 1 (P1): RRYY* (Phenotype: Round, Yellow) Parent 2 (P2): rryy* (Phenotype: wrinkled, green) Step 2: Gametes from P Generation P1 (RRYY) can only produce one type of gamete: RY* P2 (rryy) can only produce one type of gamete: ry* Step 3: First Filial (F1) Generation When the gametes from the P generation combine, all offspring in the F1 generation will have the same genotype and phenotype: Cross: RY × ry* F1 Genotype: RrYy* F1 Phenotype: All offspring will be Round, Yellow*. Step 4: Gametes from F1 Generation The F1 individuals (RrYy) are dihybrids. According to Mendel's Law of Independent Assortment, they will produce four types of gametes in equal proportions: RY* Ry* rY* ry* Step 5: Second Filial (F2) Generation To find the F2 generation, we cross two F1 individuals (or self-pollinate an F1 individual). We use a Punnett square to show the possible combinations of gametes: | Gametes | RY | Ry | rY | ry | | :------ | :--- | :--- | :--- | :--- | | RY | RRYY | RRYy | RrYY | RrYy | | Ry | RRYy | RRyy | RrYy | Rryy | | rY | RrYY | RrYy | rrYY | rrYy | | ry | RrYy | Rryy | rrYy | rryy | Step 6: F2 Genotypic and Phenotypic Ratios F2 Genotypic Ratio: 1 RRYY 2 RRYy 2 RrYY 4 RrYy 1 RRyy 2 Rryy 1 rrYY 2 rrYy 1 rryy This can be summarized as: 1:2:2:4:1:2:1:2:1 F2 Phenotypic Ratio: By grouping the genotypes by their phenotypes: Round, Yellow* (R_Y_): RRYY, RRYy, RrYY, RrYy = 9 Round, green* (R_yy): RRyy, Rryy = 3 wrinkled, Yellow* (rrY_): rrYY, rrYy = 3 wrinkled, green* (rryy): rryy = 1 The classic Mendelian dihybrid phenotypic ratio is: 9 Round, Yellow : 3 Round, green : 3 wrinkled, Yellow : 1 wrinkled, green