A cross between true breeding tall red flowered plants and true breeding short white flowered plants. Tall and red are dominant traits. What would be the expected ratios of phenotypes in the f1 and f2 generations? what is the exoected ohenityouc ratui if F2 ganeration if red and white are codominant?
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To determine the expected ratios of phenotypes in the F1 and F2 generations when crossing true breeding tall red flowered plants (TT RR) with true breeding short white flowered plants (tt rr), we can use Punnett squares.
In this case, since tall and red are dominant traits, we represent them as "T" and "R," respectively, and represent short and white as "t" and "r," respectively.
The cross between the true breeding parents would result in the following Punnett square for the F1 generation:
R R
T TR TR
t TtRr TtRr
Therefore, in the F1 generation, all offspring will exhibit the tall red phenotype, as the dominant traits (T and R) mask the recessive alleles (t and r). Hence, the expected ratio of phenotypes in the F1 generation would be 100% tall and red (TtRr).
To determine the expected ratios in the F2 generation, we need to consider the possible combinations resulting from the F1 generation.
The F1 generation (TtRr) can produce four types of gametes: TR, Tr, tR, and tr.
When we pair these gametes together, we obtain the following Punnett square for the F2 generation:
R r
T TR Tr
t TtRr Ttrr
R r
T TR Tr
t TtRr Ttrr
From this Punnett square, we can determine the expected phenotypic ratios in the F2 generation:
- Tall and red (TTRR) = 9/16 or 56.25%
- Tall and white (TtRr) = 3/16 or 18.75%
- Short and red (TtRr) = 3/16 or 18.75%
- Short and white (ttrr) = 1/16 or 6.25%
Therefore, the expected ratios of phenotypes in the F2 generation from the cross between true breeding tall red flowered plants and true breeding short white flowered plants (when tall and red are dominant) would be approximately 9:3:3:1.
Now, if the F2 generation exhibits codominance between red and white alleles (meaning neither allele is dominant over the other), the expected phenotypic ratio would be different.
In this case, from the F1 generation (TtRr), we would have the following possible genotypes in the F2 generation:
- Tall and red (TTRR) = 1/16 or 6.25%
- Tall and white (TTRr or TTrr) = 2/16 or 12.5%
- Short and red (TtRR or ttRR) = 2/16 or 12.5%
- Short and white (TtRr) = 9/16 or 56.25%
- Red and white (TTRr, TtRR, TtRr) = 2/16 or 12.5%
Thus, the expected phenotypic ratio in the F2 generation, if red and white are codominant, would be approximately 1:2:2:9:2.