Cross two plants that are both heterozygous for pod color. What fraction of the offspring will be dominant?
Use a Punnett Square.
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it would be Tt xx tt
To determine the fraction of offspring that will be dominant, we need to understand the principles of Mendelian inheritance.
First, let's define the key terms:
1. Dominant trait: A trait that is expressed over another form of the trait, known as the recessive trait. It is represented by an uppercase letter (e.g., 'B') in genetics.
2. Recessive trait: A trait that is only expressed when there are two copies of the recessive allele. It is represented by a lowercase letter (e.g., 'b') in genetics.
3. Heterozygous: Having different versions of a gene, known as alleles, for a specific trait. For pod color, heterozygous would mean having one dominant allele (B) and one recessive allele (b).
Now, let's proceed to determine the fraction of offspring that will be dominant when two plants that are heterozygous for pod color are crossed.
In this situation, we will use the Punnett square to visualize the different possible combinations of alleles in the offspring.
Here is the Punnett square for crossing two plants that are heterozygous for pod color:
| B | b |
-------------------
B | BB | Bb |
-------------------
b | Bb | bb |
In this Punnett square, the uppercase 'B' represents the dominant allele, while the lowercase 'b' represents the recessive allele for pod color.
From the Punnett square, we can see that there are four possible combinations of alleles in the offspring: BB, Bb, Bb, and bb. Among these, three combinations (BB, Bb, and Bb) have at least one dominant allele (B), while one combination (bb) has two recessive alleles (b).
Since the dominant trait is expressed whenever there is at least one dominant allele (B), and three out of the four offspring combinations have at least one dominant allele, we can conclude that the fraction of offspring that will be dominant is 3/4 or 0.75.
Therefore, 75% of the offspring are expected to exhibit the dominant pod color trait.