What is the phenotype frequency of the population with white tooth enamel?
A population of lemmings has a dominant gene for white tooth enamel, while the recessive trait was yellow tooth enamel. 23 lemmings in a population of the 325 have the recessive trait.
The specific frequency may be found by dividing the number of lemmings with yellow tooth enamel (23) by the total number of lemmings (325). This will give .0707692, multiplied by 100 percent, which will give 7.07692. What this means is 7 percent of this type of genetic cross of lemmings will produce the recessive trait, which will express itself as yellow tooth enamel. Out of every 100 lemmings born, 93 will have white tooth enamel, the dominant trait, while the remaining 7 percent will have yellow tooth enamel, the recessive trait. If you divide the 93 by the 7, you will 13.28. This essentially means that for every 14 lemmings born, 13 will have white tooth enamel, while 1 will have yellow tooth enamel. In terms of ratio expression, you could say 93:7, white enamel to yellow enamel, or reduce it to 13:1.