How can two parents with only one round allele between them (1 out of 4 alleles) produce an F1 generation in which 50% of individuals have round seeds? What appears to be the inheritance pattern for seed shape?
To understand how two parents with one round allele between them can produce an F1 generation with 50% of individuals having round seeds, we need to first understand the inheritance pattern for seed shape.
Seed shape inheritance is typically determined by a single gene with two different alleles. In this case, let's consider the alleles for seed shape as "R" for round and "r" for wrinkled. Each parent contributes one allele to their offspring, resulting in two possible combinations: RR, Rr, rR, and rr.
Based on the given information that both parents have only one round allele between them, we can deduce that one parent has the genotype Rr, and the other parent has the genotype rR. As the alleles R and r are considered to be functionally equal, they produce an identical phenotype, which is round seeds.
Now, let's examine the possible genotypes of the F1 generation resulting from this cross. When the Rr parent and the rR parent produce offspring, the following genotypes can occur: RR, Rr, rR, and rr.
Out of these four possible combinations, two have at least one round allele (RR and Rr). This means that 50% of the individuals in the F1 generation will have round seeds.
From this observation, we can conclude that the inheritance pattern for seed shape is likely to be following an incomplete dominance pattern. In incomplete dominance, neither allele is dominant over the other, and heterozygous individuals (Rr) show an intermediate phenotype compared to homozygous dominant (RR) or homozygous recessive (rr) individuals.
Therefore, in this case, having one round allele (R) is enough to produce round seeds, showing an incomplete dominance inheritance pattern.