Question

Two pure lines of corn have a mean cob length of 10 and 8 inches respectively. The polygenes involved in this exhibit an additive gene action. Crossing these two pure lines are most likely expected to produce a progeny with a mean cob length of?

• A. 10 inches
• B. 8 inches
• C. 18 inches
• D. 9 inches

Answer 1

The correct option is D 9 inches

Polygenic inheritance is also known as quantitative inheritance, where cumulative effects of multiple genes add up and express a phenotype, all the genes involved exert a small additive effect that reflects in the phenotype of the polygenic trait. A polygenic trait is characterised by the occurrence of intermediate phenotypes between the parental type, unlike Mendelian phenotypes. A cross between two pure line parents does not produce the dominant trait of one parent but instead, an intermediate trait is exhibited.
Mathematical representation of mean = sum of the terms/number of terms
$=(10+8)/2$
$=9$
The progeny of the corn will have a cob length of approximately 9 inches.