Question

a. In a pea plant, leaf color is controlled by a gene with two alleles: a dominant allele G for green leaves, and a recessive allele g for yellow leaves. A researcher crossed a plant with green leaves with a plant with yellow leaves. All the resulting offspring had green leaves. What were the genotypes of the two parental plants? (5 points)

b.  Explain briefly what is a bottleneck effect and give two examples (the examples can be imaginary). (5 points)

Answer 1

Ans

a. G - givesgreen , dominant

g - gives yellow, recessive.

If all the offsprings have green color, then the parents genotypes will be

GG - plant with Green leaves

gg - plant with yellow leaves

	G	G
g	Gg	Gg
g	Gg	Gg

All the offsprings have green leaves with this cross

So, the parents genotypes are GG and gg

2.

The bottleneck effect (also called as population bottleneck)is when the population of a species is suddenly reduced which is because of an environmental change.

The bottleneck effect is a example of genetic drift when the size of a population is severely reduced.

Natural disasters like earthquakes, floods etc can reduce a population size , killing most indviduals and leaving behind a small, random assortment of survivors.

Such events can reduce the variation in the gene pool of a population, then only a smaller population, with a smaller genetic diversity, remains to pass on genes to future generations.

Examples

1. An example of a population bottleneck is that happened in the Black Robin of New Zealand, which shows every specimen is a descendant of a single female, called Old Blue, happened due to bottleneck effect.

2. The golden snub-nosed monkey suffered low genetic diversity due to bottleneck effect . it is suspected that an environmental event has caused the bottleneck effect.