Question

A garden pea plant produced axial white flowers. Another of the same species produced terminal violet flowers. Identify the dominant traits.

Answer 1

The principle of dominance states that, when two genes are found in an organism one of them masks the presence of another one, in other words one gene is dominant and stops the expression of the other gene.

Complete answer:
To solve this question, we have to know about the law of dominance. The law of dominance explains the expression of only one characteristic of the parents during monohybrid cross in F1 generation and expression of both the alleles in the F2 generation. During some crosses it has been observed that in the F1 generation the phenotypic characteristics of the offspring do not resemble in either of the parents, this is because of incomplete dominance and in some cases, both the alleles in a heterozygote express themselves at the same time, this phenomenon is termed as codominance.
So, Mendel worked on the inheritance of genes, to make this understanding he crossed pea plants with two different characters, that is seeds with yellow colour and round in shape cross with seed with green colour and wrinkled shaped. After the crossing he observed that in the F1 generation, yellow colour and round shapes seeds are produced, hence, it is concluded that yellow colour is dominant over green colour and round shape is dominant over wrinkled shape. Depending on this theory the axial white flower is crossed with terminal violet flowers.

Now, to determine the dominant traits between the axial white flower and terminal violet flower, we should carry out a cross between the parents axial white (AAww) and terminal violet (aaWW) exhibits the contrasting traits.
During crossing between the parents; AAww X aaWW
Gametes are; Aw X aW, when crosses
F1 generation shows, AawW (Axial violet)
Selfing;

Gametes	AW	aW	Aw	aw
AW	AAWW	AaWW	AAWW	AaWw
aW	AaWW	aaWW	AawW	aawW
Aw	AAwW	AaWw	AAww	aAww
aw	AaWw	aaWw	Aaww	aaww

In F2 generation; its gives the ratio of 9 axial violet : 3 axial white : 3 terminal violet : 1 terminal white.
Therefore, the axial violet is dominant.

Note: Co-dominance is the phenomenon in which both the alleles in a heterozygotes express themselves at the same time. Co-dominance is observed in blood grouping of humans. It is also an example of multiple alleles as more than two alternative forms of gene found on a particular locus are considered as the multiple alleles. It is formed as a result of repeated mutation of the same gene but in different directions.