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1) A particular variety of corncan have short, medium, or tall stems, and it can

ID: 5122 • Letter: 1

Question

1)      A particular variety of corncan have short, medium, or tall stems, and it can have red, purple,or blue kernels. You cross a tall red variety with a short, blueone and obtain a medium, purple F1. You intercross theF1 to obtain an F2. The F2 showsnine phenotypic classes as follows:

Tall red

17

Tall purple

29

Tall blue

15

Medium red

34

Medium purple

63

Medium blue

31

Short red

16

Short purple

31

Short blue

15

Provide a simple genetic explanation of these results. Chooseyour own symbols and write the genotypes of the parental strains,the F1 and each F2 phenotypic class.

Tall red

17

Tall purple

29

Tall blue

15

Medium red

34

Medium purple

63

Medium blue

31

Short red

16

Short purple

31

Short blue

15

Explanation / Answer

TT, ===-tall

Tt----medium

tt- ==short


RR, =======red


Rr---purple


rr========-blue


                   tall red       x   shortblue


             TTRR        x           ttrr

                   TR             tr-gametes


                             TR tr          medium,purple F1


TRtr          medium,purple F1        x              TR tr          medium,purple F1


TR      Tr          Rt           tr                   TR      T r         Rt           tr----------- gametes


TR TR             Tallred


T r Tr           Tall blue


R t   TR          Mediumpurple


tr TR         Mediumpurple


TR T r       Tall purple



T r Tr     Tall blue


   R t T r       Medium blue


   tr T r       Medium blue


TR R t    Mediumred


T r R t Mediumpurple


R t R t   Short red


tr R t Short purple


TR tr Medium purple


T r tr Medium blue


R t tr Shortpurple


tr tr Short blue