Question

1. What prediction does the neutral theory make that is not true and what modification was made to its assumptions to produce a new theory created by Ohta that better fit the data?

A) genetic change should be constant/most mutations are under very weak selection

B) evolutionary rate should be a function of mutation rate per generation/most mutations are under very weak selection

C) evolutionary rate should be a function of mutation rate per generation/drift is not acting

D) evolutionary rate should be a function of mutation rate per generation/most mutations are under very strong selection

E) genetic change should be constant/most mutations are under very strong selection

2. In a hypothetical situation a flu pandemic is spreading across the world (in humans). The virus is sequenced and is found to be an H1N3 virus. A phylogeny of viruses find that this virus is most closely related H1N1 viruses but that the gene for N3 is most closely related to the 'N' gene in pigs. What is the most likely evolutionary scenario for this situation?

A) The pig virus has switched hosts to attack humans

B) Human and pig viruses recombined in a host cell

C) Human and pig viruses mated and recombined

D) The viral gene for 'N' underwent extensive parallel evolution

E) N1 mutated to N3

Answer 1

1.A) genetic change should be constant/most mutations are under very weak selection

The main difference between Ohta’s nearly neutral theory and Kimura’s neutral theory is while Kimura put his focus on so-called “strictly neutral mutations” (this phrase is specified by Ohta), Ohta was more interested in the evolutionary mechanisms of the “border line mutations” or the “nearly neutral mutations,” (i.e. mutations which are not strictly neutral nor are strongly selected).

The most notable yet overlooked difference between these two theories is the effect of population sizes. Simply, population size does not effect on neutral mutations. For nearly neutral mutations in small populations, the effects of selection are also extremely limited and the fate of them is also determined by random genetic drift just like neutral mutations. However, the effects of selection are not ignorable in a large population for nearly neutral mutations.

2.D) The viral gene for 'N' underwent extensive parallel evolution

.Here this is the possibility.Parallel evolution refers to the evolutionary process wherein two or more species in the same environment develop similar adaptation or characteristics.

Considering opton A, The pig virus has switched hosts to attack humans ,it needs a special mechanism which is not mentioned in question.

Considering opton B & C, Intragenic recmbination is extremely rare.

Considering option E, N1 mutated to N3 the statement says that they are closely related, when mutated does not relates that closely and also the new strain become recessive and on a long course ,it can be removed from population

so the possibility is option D