The easiest way to answer this question, is to have remembered what type of cross will produce a 9:3:3:1 phenotypic ratio. However, if you don't remember that, then the only thing to do is to make repeated punnett square crosses until you find the one that results in the phenotypic ratio you are looking for. You can narrow down the possibilities by realizing that all of the phenotypes are present in the offspring so you can rule out right away crosses that only involve homozygous traits. For example crossing two individuals with a HHEE genotype will not result in any offspring that have the low oil / two seed phenotype (hhee). Below is a blank punnett square for you to perform crosses in.






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You have not been given enough information to answer this question. There are several combinations of the F1 generation that could result in the observed phenotypic ratio of the F2 generation. Below is a blank punnett square with which you can experiment on different crosses to see that this is true.




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What you want to do here is a test cross. You need to cross the high oil / four seed plants with another of known genotype . Because typing genes is expensive and slow, you will do best to choose a plant from which the genotype can be determined by what phenotype it has. Which of the following gene combinations fit this requirement?

You also want to choose a plant that if crossed with a heterozygous individual will result in offspring whose phenotypes reveal the presence of the recessive allele. Which of the following gene combinations fit this requirement?



With these requirements in mind, which genotype should the farmer use in her test cross?




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