a)You produce a strain of knockout mice in which you have deleted the A gene to

Question

a)You produce a strain of knockout mice in which you have deleted the A gene to be Ako. You don’t know whether a functioning A gene is essential for the animals to survive, ie you wish to know whether Ako Ako homozygotes are lethal. Examining the progeny of Ako A X Ako A mating what results would you expect if Ako is a lethal gene or not. Assume you can directly identify only the presence Ako alleles and not A by molecular techniques. Thus you can distinguish AA from Ako—individuals only.

b)If the AkoAko are viable then the progeny of the Ako A X Ako A mating would include both Ako A and AkoAko offspring. How would you distinguish the two by test mating.

Explanation / Answer

After examining the Punnett square, it is revealed that 50%of offsprings will be Ako A and 25%offspring will be AkoAko.

Performing the test mating, because there is no available test for identifying 'A'.

Step 1: A test individual is taken. Hypothesis is assumed that it is a carrier (Ako A)

Step 2: This test individual is crossed with homozygous recessive partner. 'Let's say cross is with Ako Ako.

Step 3: If any affected individuals are found, this means that tested animal is carrier and hypothesis is correct. In this case, If the entire progeny survives, means Ako Ako is not lethal; If 50% progeny survives, it means that Ako Ako is lethal. The rest 50% progeny is Ako A. 50% progeny will have the affect of knockout gene; the rest 50% will not have.

Thus, mating between parent and its heterozygous offspring is a test for any recessive gene.

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