Question

A pure-breeding short strain of pea produces plants that are 20-26 cm in height. A pure-breeding tall strain of pea produces plants that are 46-55 cm in height. When these pure-breeding strains are crossed, the F1 plants range in height from 32 to 48 cm. Which of the following statements about phenotypic variance in height is true?A) The F1 variance is due only to genetic factors.B) The F1 variance is due only to environmental factors.C) The F1 variance is due to a combination of genetic and environmental factors.D) The variance in the tall parental strain is due to a combination of genetic and environmental factors.

Answer 1

The correct answer is: B) The F1 variance is due only to environmental factors.

According to Mendelian genetics: he crossed two purebred parents with differing traits to be sure that there were no other factors contributing to the outcome of the cross. When two purebred parents are crossed, all of the offspring should be genetically the same (heterozygous).

In the example above, we can see that there is phenotypic variance among the offspring, so we can conclude that it must be due only to environmental factors.