Final answer:
A cross between two heterozygous tall pea plants yields offspring with a genotypic ratio of 1 TT : 2 Tt : 1 tt, which is a 1:2:1 ratio. However, when considering the phenotypic results, the standard ratio is 3:1 for tall to dwarf plants.
Step-by-step explanation:
Predicting Offspring Genotype using a Punnett Square
To predict the offspring from a cross between two heterozygous tall pea plants, a Punnett square is utilized. In this scenario, tallness (T) is dominant over dwarf (t). Since both plants are heterozygous, their genotype is Tt. To set up the Punnett square, we list the possible gametes from each parent on the top and side of a grid. Then, we fill the grid with the possible genotypic outcomes for the offspring.
Parental Gametes: T and t (for both plants)
The genotypic ratio of the offspring is therefore 1 TT : 2 Tt : 1 tt, which simplifies to a 1:2:1 ratio. This means in a large number of offspring, one would expect approximately one-fourth to be homozygous dominant (TT), half to be heterozygous (Tt), and one-fourth to be homozygous recessive (tt).
The answer to the original question would be (d) 3:1, as this is the standard genotypic ratio for a monohybrid cross between two heterozygous individuals when we look at the phenotypic results.