Question

Question statement
A. Two pea plants with green pods, Gg X GG, were crossed. Complete the given Punnett square to show the result of this cross..
B. What percentage of the offspring produced by this cross will most likely have green pods?

| G| g
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G| |
G| |

Answer 1

The genotype is the genetic constitution of an organism while the observable characters of an organism constitute its phenotype. The phenotype is the result of how a genotype is expressed and both of these can be found out through Punnett square.

Complete answer: A visual diagram showing a monohybrid cross between two parents is called the Punnett square. The genotypes and the phenotypes which result from the various combinations of gametes can easily be determined by Punnett squares. It was devised by Reginald C. Punnett.
In this each of the possible gametes are placed in an individual column or a row. The gametes are then arranged in then all possible combinations and the resulting genotypes are entered in the boxes along with phenotypes.

| G| g
---|---|---
G| GG| Gg
G| GG| gg

Monohybrid cross is when only a single pair of contrasting or differentiating characters is considered in a cross. For example, the cross given in the question is a monohybrid cross as only one contrasting character i.e. the color of the pods is considered here in the question.
The genotypic ratio of the cross is – GG : Gg : gg - 2 : 1 : 2.
The phenotypic ratio of the cross is- Green : white – 3 : 1
The percentage of offspring from this cross that is most likely to have green pods is – 3/4 X 100= 75.
The two forms of the trait appear in the F2 generation in a ratio of three dominant to one recessive i.e. 3:1.

Note: A heterozygote possesses two contrasting characters or alleles but only one of the two is able to express itself, while the other remains hidden. The gene which gains expression in F1 is dominant while the allele that does not express itself in F1 is recessive allele.