In tomatoes, regular leaves (L) are multilobed and serrated and potato leaves (l) are broad, smooth, and single (Image 1). Red fruit (F) is dominant to yellow fruit (f). A cross is carried out between two pure lines of tomato plants, one having regular leaves and red fruit and the other having potato leaves and yellow fruit. The F1 generation all have regular leaves and red fruit. The F1individuals are
In tomatoes, regular leaves (L) are multilobed and serrated and potato leaves (l) are broad, smooth, and single (Image 1). Red fruit (F) is dominant to yellow fruit (f).
A cross is carried out between two pure lines of tomato plants, one having regular leaves and red fruit and the other having potato leaves and yellow fruit. The F1 generation all have regular leaves and red fruit. The F1individuals are then crossed with one another.
Complete a Punnett square to determine the expected F2 progeny on the basis of Mendel’s Law of Independent Assortment, which states that the alleles for one gene segregate independently of the alleles for other genes during gamete formation.
The information below represents two sets of data collected from the above cross.
| Data Set 1 | Data Set 2 | |
|---|---|---|
| Regular Red |
26 | 846 |
| Regular Yellow |
15 | 273 |
| Potato Red |
6 | 287 |
| Potato Yellow |
12 | 94 |
| Total |
59 | 1 500 |
- Convert the expected phenotype ratio into the expected probability for each of the four phenotypes and record them in the table below. (Record your answers as a value between 0 and 1 rounded to two decimal places.)
Example of calculating expected probability:
To convert from the expected phenotypic ratio to the expected probability convert the ratio to a fraction and then the fraction to a decimal
If expected phenotype ratio is 9:3:3:1, this means that
9/16 regular red (both dominant L_F_)
3/16 regular yellow (dominant recessive L_ff )
3/16 potato red (recessive dominant llF_ )
1/16 potato yellow (both recessive llff)
Expected probability of regular red: 9/16 = 0.56
1. Data set 1 and 2 are the actual data observed from the cross. Calculate the observed probability of the four possible phenotypes for each data set by dividing the number of progeny in each class by the total number of progeny and record these in the table below. (Record your answers as a value between 0 and 1 rounded to two decimal places.)
| Observed Probabilities | |||
|---|---|---|---|
| Phenotypes | Expected Probabilities | Data Set 1 |
Data Set 2 |
| Regular Red | |||
| Regular Yellow | |||
| Potato Red | |||
| Potato Yellow |
2. Data set 1 is a from a small sample size and data set 2 is from a large sample size. Compare each data set to the expected probabilities. Explain any differences that you see in how different the observed results are from the expected results between the two data sets.
3. Compare the expected probabilities of each phenotypic class to the observed probabilities for data set 2 (large sample size) to determine if the genes for leaf shape and fruit colour assort independently.
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