Question

In 1983, Dr. Barbara McClintock was awarded the Nobel Prize in Medicine for her research on corn genetics. Kernels of Indian corn come in different colors, such as purple, yellow and white. Sometimes the individual grains are purple with white streaks. This streaked effect defies principles of genetics because individual grains may be multicolored rather than a single color. The movement of transposons on chromosomes may result in colored, non-colored and variegated grains that do not fit traditional genetic ratios based solely on chromosome assortment during meiosis and random combination of gametes. The explanation for this phenomenon involves jumping genes or what we now refer to as transposons. McClintock's work with transposons calls into question the model of inheritance patterns we have learned in the past that is the basis of Mendelian genetics. Which model would be MOST weakened by McClintock's discovery? A) A B) B C) C D) D

Answer 1

Answer

A) Segregation

Explanation:

In Mendel's law of Segregation, each allele is inherited separately from each other within gametes- each gamete can only carry one gene.

Transposons refute this; here, variegation (regions of multiple colors) may occur due to "jumping genes" leading to multiple phenotypic variants like a multicolored seed,instead of a seed retaining one solid color. Mendelian ratios, thus, are not observed.

This is seen in instances such as Indian corn- these seeds may be purple, red, green and yellow. Variegation of seed color can occur to produce multicolored grains of purple and white.