two tall pea plants with yellow seeds and smooth pods are crossed. all of the offspring are tall. three offspring have smooth pods and one has wrinkled pods. the lake for wrinkled pods
a. must be dominant because the tree does not appear in the parent plants
b. must be recessive because the tree does not appear in the parent plant
c. must be dominant because the trait appears in the parent plants
d. must be recessive because the trait appears in the parent plants
must be recessive because the tree does not appear in the parent plant
To determine whether the trait for wrinkled pods is dominant or recessive, we need to understand the principles of genetics and how traits are passed from parents to offspring. In this scenario, we have two tall pea plants with yellow seeds and smooth pods that were crossed. All of their offspring are tall, but there is variation in the pod texture, with three offspring having smooth pods and one having wrinkled pods.
The first step is to assign symbols for the traits involved. Let's use the following:
- Tall plant (T) as the dominant trait.
- Short plant (t) as the recessive trait.
- Smooth pods (S) as the dominant trait.
- Wrinkled pods (s) as the recessive trait.
By crossing the two original plants, we can deduce their genetic makeup:
Parent 1: Tall, yellow seeds, smooth pods (TYS)
Parent 2: Tall, yellow seeds, smooth pods (TYS)
Based on the information provided, all of the offspring are tall. This indicates that the tall trait is dominant since it appears in every offspring. Therefore, we can conclude that both parent plants must be heterozygous (Tt) for height.
Now let's focus on the factor of pod texture. Three of the offspring have smooth pods, while only one has wrinkled pods. Based on our genetic symbols, the possible genotypes for the parent plants are:
TYS = Tall, yellow seeds, smooth pods (dominant for all traits)
TyS = Tall, yellow seeds, wrinkled pods (recessive for pod texture)
When two plants with the genotype TYS and TyS are crossed, the predicted offspring genotypes can be determined using a Punnett square:
TYS TyS
TYS | TYS TYS
TYS | TYS TYS
According to the Punnett square, all the possible offspring genotypes are TYS. None of them have the TyS genotype, which means that the wrinkled pod trait is not dominant and is only visible when both parents carry the recessive allele (tys).
In conclusion, based on the appearance of the trait in the parent plants and the observation of the offspring, the trait for wrinkled pods must be recessive (d), and the correct answer is option d.