A student in your lab isolates six mutant strains of yeast that produce pink col
ID: 186719 • Letter: A
Question
A student in your lab isolates six mutant strains of yeast that produce pink colonies (a recessive mutation), wildtype colonies are white. The student performs a complementation test t determine if any of the six strains contain allelic mutations. Below is the table of the results. 1. 1 pink White White pink White White 2 white | pink | White | White | white | white 3 White White pink White pink White 4 pink White White pink White White 5 White White pink White pink White 6 White White White White White pink How many mutant genes are represented in this collection of strains? Support your answer by putting the strains into complementation groups. (3) a. Provide a genetic explanation (allelic and non-allelic) for why diploids made from strains 5 and 3 produce pink colonies. (1) b. You are provided with 5 mutant strains of yeast that produce tiny colonies (known as petite). They belong to the following complementation groups: (1,5) (2) (3,5) (4). 2. Explain why strain 5 belongs to more than one complementation group. (1) a.Explanation / Answer
a)
Wild type colonies are white. The mutant colonies are pink.
Mutant 1 and 4 show pink color; this means that they complement each other. This means that 1 and 4 are separate genes. Similarly mutant 3 and 5 also complement each other. So, these are separate genes/mutants. There are 2 complementation groups.
2 and 6 do not complement any strain. They are white in all cases. This means that 2 and 6 are same.
So, there are a total number of four mutants involved; 1, 3, 4, and 5. Note that 2 and 6 are wild type.
b) Wild type 3 is white. Similarly, wild type 5 is also white. A cross between wild type 3 and wild type 5 will be white.
Now, in this case, a cross between 3 and mutant 5 is giving pink colonies and not white. This means that a mutation has occurred in the two wild type strains; now 3 and 5 are not same. They have become different genes. In other words, they both are complementing each other to produce a different color, i.e. pink.
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