Question

1. Which of the following demonstrates disruptive selection?: *

(A) The size of black bears decreased during interglacial periods of the ice ages in Europe based on fossil evidence.

(B) Medium birth weight babies survive more frequently than either low or high birth weight babies.

(C) The increase in beak size in a population of finches due to the abundance of a certain type of seed used for food.

(D) The gene coding for rabbit fur color shows incomplete dominance, and rabbits with white fur or black fur show a survival advantage compared to rabbits with gray fur.

2.

What is the primary function of rRNA? : *

(A) rRNA encodes the messages for genes which are then translated by ribosomes in the cytoplasm.

(B) rRNA anticodons are paired with codons by ribosomes to assemble nascent peptides during translation.

(C) rRNA is the nucleic acid component of ribosomes and binds RNA messages during translation.

(D) rRNA encodes a gene in the nucleus of a cell prior to transcription by host polymerases.

Answer 1

1. D is the right answer. In disruptive selection, both the extremes of the trait are selected or favoured over the median trait. Likewise, in the rabbits there are 3 fur colors are produced due to incomplete dominance where the white or black fur rabbits are favoured and not the rabbits with grey fur. The grey fur here is the median trait (incompletely dominant trait) and white and black fur are the two extremes of the trait and thus disruptive selection is seen.