If an offspring has the genotype a) Aa or b) AaBB whatpossible combinations of p
ID: 2515 • Letter: I
Question
If an offspring has the genotype a) Aa or b) AaBB whatpossible combinations of parental genotypes can exist for eachoffspring? I know how to do Punnett squares, but I'm not sure I amworking backwards well enough to determine all of the variouspossibilities. For Aa, I have the possibilities of AA and aa, but will AA andAa as well as Aa and Aa work too? I know these will also produceother offspring genotypes, but they do include Aa. Should all ofthese be included? Am I missing any. For AaBB, I have the possibilities of AB and aB, but I'm surethat I am missing some for this. Is there a way to determine thisother than doing trial-and-error? If an offspring has the genotype a) Aa or b) AaBB whatpossible combinations of parental genotypes can exist for eachoffspring? I know how to do Punnett squares, but I'm not sure I amworking backwards well enough to determine all of the variouspossibilities. For Aa, I have the possibilities of AA and aa, but will AA andAa as well as Aa and Aa work too? I know these will also produceother offspring genotypes, but they do include Aa. Should all ofthese be included? Am I missing any. For AaBB, I have the possibilities of AB and aB, but I'm surethat I am missing some for this. Is there a way to determine thisother than doing trial-and-error?Explanation / Answer
A. This is a one gene cross Basically the only thing you can infer from the given phenotypes ofthe perogeny (offspring) is that it received an A allele from oneparent and an a allele from the other parent so all punnet squarecombinations with a parent with large A and the other with a smalla will work the parents could be ( AA x aa or Aa x Aa or AA x Aa orAa x aa) all of these combinations will yield at least oneoffspring with the Aa genotype. B. This is a two gene cross so things get a little more complex thepunnet square should have 16 blocks if you did not already knowthat. You can again have all of the same A allelecombinations but to that you can also have any of the the three Ballele combinations for the parents (BB x Bb or Bb x Bb or BB x BB)each can yield the BB ofspring combinations so there are a total of24 parental combinations for part B. the 4 A allele combinationstimes the 3 B allele combinations and then once more by 2 becausetheir are 2 genes so they can be switched within eachparental. I hope this helps and I will gladly clarify further if need be.just message me