Question

A plant called blue-eyed grass normally produces blue flowers. However, plants producing white flowers also occur, because an allele for the gene coding for the protein that produces the blue pigment is non-functional. This white-flowered allele (W) is dominant to the blue-flowered allele (w), but generally occurs at very low frequency in populations. Suppose you crossed a homozygous dominant plant with a homozygous recessive plant, and the result is 16 seeds. If you plant these, assuming simple Mendelian genetics, how many do you predict are blue-flowered?

= 0

Now suppose you take two of these offspring and cross them and obtain 20 seeds, how many of thier offspring do you predict are blue-flowered?

= 5

Blue-eyed grass is usually about 10 cm tall. However, there are individuals twice this size because of the presence of a mutation in a height gene. Tall individuals are homozygous recessive for this height gene (hh), while short individuals are either homozygous dominant (HH) or heterozygous (Hh). Suppose you crossed two heterozygous white-flowered and short plants (i.e. heterozygous for both traits) and the resulting offspring had genotypic ratios of 9:3:3:1. Based on this result, what can you say?

-the genes for these traits are on different chromosomes

Suppose you studied a population of blue-eyed grass, and found that there are 9025 blue-flowered plants out of a total population of 10,000. Assuming Hardy-Weinberg equilibrium, what is the frequency of the white allele (W) in the population?

= 0.05

Suppose you went back to this population after one year, and found that the frequency of the blue-allele was at 0.88. Assuming Hardy-Weinberg equilibrium, how many white flowered plants are there if there are 10000 in total?Based on this result, what should you conclude from this result?

= 2256

Based on this result, what should you conclude from this result?

-the population evolved via gene flow

-The population evolved via genetic drift

-the population evolved via sexual selection

-None of these answers are correct

-the population evolved via natural selection

Answer 1

Suppose you studied a population of blue-eyed grass, and found that there are 9025 blue-flowered plants out of a total population of 10,000. Assuming Hardy-Weinberg equilibrium, what is the frequency of the white allele (W) in the population?

In this population, the white flowered plants are 975. Blue flowered plants are 9025.

Suppose you went back to this population after one year, and found that the frequency of the blue-allele was at 0.88

In this population, white flowered plants are 2256.

So, after some time the population is having more white flowered plants. The blue flowered plants have reduced in number. This only shows that there is some selective pressure happening in the population.There is no indication of any new population entering in to the region. So it can't be gene flow. No indication of any chance selection happening, so no genetic drift. One particular sex is also not selected, so there is no sexual selection observed. But because the allele frequency is increasing, we consider that there is some selection and evolution happening in the population. So we can simply say that the population is evolving via natural selection.