If an F1 plant is backcrossed with the sweet, unspotted parent, the phenotypic proportion that is expected in the offspring will be in the ratio of 1:1:1:1.
<h3>What is Backcross?</h3>Backcross may be defined as a type of cross where the F1 hybrid is crossed with either the recessive or dominant traits.
This question typically represents a dihybrid cross implicating two genes, one coding for fruit taste and the other for spot color. The allele for bitter taste (B) and yellow spot (S) is dominant over the allele for sweet taste (b) and no spot (s) respectively.
So, a heterozygous F1 resulting from a cross between a purebred dominant (bitter fruit, yellow spot) and purebred recessive (sweet fruit, no spot) will have a BbSs genotype.
When the F1 hybrid BbSs is backcrossed with the sweet, unspotted parent (bbss), the phenotypes with their proportions are given below:
- Bitter fruit, yellow spot (BbSs, 1)
- Bitter fruit, no spot (Bbss, 1)
- Sweet fruit, yellow spot (bbSs, 1)
- Sweet fruit, no spot (bbss, 1).
The Punnett square of this cross is described below:
Therefore, if an F1 plant is backcrossed with the sweet, unspotted parent, the phenotypic proportion that is expected in the offspring will be in the ratio of 1:1:1:1.
To learn more about Dihybrid cross, refer to the link:
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