Answer:
If crossing plants with hairy leaves and smooth leaves produces plants with smooth leaves in F1, the phenotypic ratio of plants with smooth leaves:hairy leaves in F2 will be 3:1.
Explanation:
It is assumed that, if the first descendants of this cross presented smooth leaves, this represents the dominant characteristic.
If in the crossing of two plants, the parental generation consists of two <u>pure plants for the characteristic aspect of the leaf</u>, one with hairy leaves (s) and another with smooth leaves (S), the first filial generation (F1) will be of hybrid plants with a phenotype of smooth leaves (Ss), which represents the dominant characteristic.
<u>Parental Generation</u>:
- Smooth leaves SS
- Hairy leaves ss
<u>Punnett Square F1</u>
<em>Alleles S S</em>
<em>s Ss Ss</em>
<em>s Ss Ss</em>
F1 : 100% plants with smooth leaves Ss
The second filial generation (F2) results from the crossing of F1 individuals, so:
<u>Punnett Square F2</u>
<em>Alleles S s</em>
<em>S SS Ss</em>
<em>s Ss ss</em>
The result of the offspring in F2 is:
<u>Genotype
</u>
- <em>Pure smooth leaves SS 25%</em>
- <em>Smooth hybrid leaves Ss (heterozygous)
: 50%</em>
- <em>Pure hairy leaves ss: 25%</em>
Genotipic ratio: pure smooth leaves:hybrid:pure hairy leaves 1:3:1
<u>Phenotype</u>
- <em>Smooth leaves SS + Ss: 75%</em>
- <em>Hairy leaves ss: 25%</em>
So the phenotypic ratio of smooth leaves: hairy leaves will be 3:1.