| Characteristic | Dominant Allele | Recessive Allele |
| Plant Height | Tall | Dwarf |
| Flower Color | Purple | White |
| Seed Color | Yellow | Green |
| Pod Shape | Full | Constricted |
| Pod Color | Green | Yellow |
| Seed Shape | Round | Wrinkled |
| Step 1 | Given that Tall (T) is dominant and short (t) is recessive, draw a two by two Punnett Square to determine the results of a mono-hybrid (single factor) cross between two heterozygous organisms. |
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| |
| Step 2 | Place the alleles (T and t) from one parent above the squares. |
| T |
t |
| |
|
| |
| Step 3 | Place the alleles (T and t) from the other parent on the left side of the square. |
| T |
t |
|
| T | |
|
| t | |
| Step 4 | Systematically, place the red capital T in the each of the squares below it. Then, place the red small t to the right side in the squares below it. |
| T |
t |
|
| T |
T |
t |
| t |
T |
t |
| Step 5 | Next, place the purple capital T in the each of the squares to the right of it and do the same with the small purple t . |
| T |
t |
|
| T | T T |
T t |
| t |
T t |
t t |
| Step 6 | Determining the genotypes that result from a mono-hybrid cross: |
| A | Count the number of homozygous dominant alleles (T T) and shade the square yellow. |
| B | Count the number of heterozygous alleles (T t and T t) and shade the squares gold. |
| C | Count the number of homozygous recessives ( t t ) and shade the square yellow-green. |
| Your result should be: 1 homozygous dominant, 2 heterozygous, and 1 homozygous recessive (1:2:1 ratio). |
|
| T |
t |
|
| T | T T |
T t |
| t |
T t |
t t |
| Step 7 | Determining the Phenotypes in the preceding problem: |
| A | Locate the squares that contain at least one homozygous dominant allele, (T OR T.) |
| B | Locate the square that contain two homozygous recessive alleles, (t AND t.) |
| Your results should be 3 Tall pea plants (T T , T t , T t) and 1 Dwarf pea plant (t t) | |
