A botanist studying water lilies in an isolated pond observed three leaf shapes in the population: round, arrowhead, and scalloped. Marker analysis of DNA from 125 individuals showed the round-leaf plants to be homozygous for allele r1, while the plants with arrowhead leaves were homozygous for a different allele at the same locus, r2. Plants with scalloped leaves showed DNA profiles with both the r1 and r2 alleles. Frequency of the r1 allele was estimated at 0.81. If the botanist counted 20 plants with scalloped leaves in the pond, what is the inbreeding coefficient F for this population?

Key Concepts

Alleles and Genotypes

Alleles are different versions of a gene that can exist at a specific locus on a chromosome. In this case, the botanist identified two alleles, r1 and r2, which determine the leaf shapes of the water lilies. The genotype of an individual, which is the combination of alleles it possesses, influences its phenotype, or observable traits. Understanding how these alleles interact is crucial for analyzing genetic variation in the population.

Homozygosity and Heterozygosity

Homozygosity occurs when an individual has two identical alleles at a locus, while heterozygosity refers to having two different alleles. In the observed population, round-leaf plants are homozygous for allele r1, and arrowhead plants are homozygous for allele r2. Scalloped-leaf plants are heterozygous, possessing both alleles. This distinction is important for calculating genetic diversity and understanding the inbreeding coefficient.

Inbreeding Coefficient (F)

The inbreeding coefficient (F) quantifies the likelihood that two alleles at a locus in an individual are identical by descent, indicating the level of inbreeding in a population. A higher F value suggests increased homozygosity and reduced genetic diversity, which can affect the population's adaptability. To calculate F, one must consider allele frequencies and the observed genotypes, particularly in the context of the scalloped-leaf plants in this study.