Researchers studying a small milkweed population note that some plants produce a toxin and other plants do not. they identify the gene responsible for toxin production. the dominant allele (t) codes for an enzyme that makes the toxin, and the recessive allele (t) codes for a nonfunctional enzyme that cannot produce the toxin. heterozygotes produce an intermediate amount of toxin. the genotypes of all individuals in the population are determined (see chart) and used to determine the actual allele frequencies in the population.

Small milkweed toxin production is the result of incomplete dominance.

There two types of alleles:

T = Dominant allele.

t = Recessive allele.

And these two alleles will produce three types of genotypes:

Dominant homozygous= TT = The production of high amount of toxin.

Recessive homozygous = tt =The production of no toxin.

Dominant heterozygous = Tt = The production of intermediate amount of toxin.

Incomplete dominance is a genetic phenomenon in which dominant allele is not fully expressed in form of heterozygous genotype.

The dominant allele expression depends upon the frequency of allele in genotype.

rocks and weathering-matching

volcanoes (an event in the geosphere) release a large amount of particulate matter into the atmosphere. these particles serve as nuclei for the formation of water droplets (hydrosphere). rainfall (hydrosphere) often increases following an eruption, stimulating plant growth (biosphere).