Chapter 4, Problem 18P

Summary Introduction

To analyze:

In the given experiment, they have taken four petunias true breeding for flower color. When there is no pigment synthesis, white color flowers produced. When only blue or only red color pigments are synthesized, blue and red color flowers are produced respectively. When red and blue color pigments are synthesized, purple colored flowers are produced. There are two different biochemical pathways to synthesize flower color pigments. In pathway 1, gene A is responsible to produce the enzyme that catalyzes the conversion of colorless pigments into blue color. In pathway 2, gene B is responsible to yield the enzyme that catalyzes the translation of colorless pigments into red color. Both genes are separated independently.

Determination of possible genotypes for true breeding red petunias.

Determination of possible genotypes for true breeding blue petunias.

Determination of expected phenotypic distribution of F2 progeny.

Introduction:

Epistasis is the process where one gene influences the phenotypic effect of another gene. The gene which influences another gene is termed as the modifier gene. In many living organisms, most of the traits are influenced by association of various genes.

Mendel's second law is the law of independent assortment. According to this law, when cross is done for more than one trait (two or more), the traits organize independently (selection of one trait is not dependent on another), so different phenotypes occur with equal probability.