For the cross Aabb × aaBb, what is the expected genotype ratio...

Question

For the cross Aabb × aaBb, what is the expected genotype ratio? What is the expected phenotype ratio?

Accepted Answer

Hi, everyone. Let's take a look at this practice problem together. A cross is performed between individuals with the big A little A big B, little B and big, a little A big B big B Gina types. What is the phenotype pick ratio expected for this cross? Our answer options are a 9 to 3 to 3 to 1 B 12- C 12 to 2 to 1 to 1 or D 9 to 7. So this question is asking us to solve for the phenotype pick ratio for a di hybrid cross, which is a cross between two individuals with two traits to determine the phenotype ratio. We need to know the jena types for the offspring. So what are those Gina types will solve this by doing a punnett square for the two individuals. Before we do that pertinent square, we need to determine the possible gammas each parent can pass on. We'll begin with individual big a little A big B little B to determine this individual's possible gametes. Let's do a punnett square on the screen. The punnett square shows the first trait A lil's big, a little A in the first rail and in the first column is the second traits, a little's big B, little B. This cross results in four different possible gammy combinations. Big A big be big. A little B, little A big B and little A little B. Now we will repeat that process for the second individual with genotype big a little A big B big B. The results of that punnett square are on the screen. The first treat the lil's again are in the top row, big a little A and the second traits alleles big B, big B are in the first column. The four possible gammy combinations for this individual are big. A big be big. A big B little A big B and little A big B. Now we know all possible gametes and can fill in a punnett square for the cross between two individuals and solve for the offspring gina types. The results of that pun it's square are on the screen. The possible gametes from the first individual big a little A big b, little B are on the top row. The possible gametes for the second individual big a little A big B big B are in the first column. Analyzing the punnett square. There are two different types, the first phenotype. So that first phenotype, there are 12 offspring that are dominant for both traits and I am highlighting those individuals in orange. So 12 offspring dominant for both traits. The second phenotype is four offspring are recessive for the first trait and dominant for the second trait. And I am highlighting, highlighting those individuals in a light purple. Therefore, the phenotype pick ratio is 12 - four. That means the correct answer is option B- 12-4. Alright, everyone. I hope you found this helpful and I'll see you soon for the next practice problem.

For the cross Aabb × aaBb, what is the expected genotype ratio? What is the expected phenotype ratio?

Key Concepts

Dihybrid Cross and Genotype Combinations

Mendelian Inheritance and Independent Assortment

Phenotype Determination from Genotype

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