A dark-red strain and a white strain of wheat are crossed and produce an intermediate, medium-red F1. When the F1 plants are interbred, an F2 generation is produced in a ratio of 1 dark-red : 4 medium-dark-red : 6 medium-red : 4 light-red : 1 white Further crosses reveal that the dark-red and white F2 plants are true breeding.

a. Based on the ratios in the F2 population, how many genes are involved in the production of color?
b. How many additive alleles are needed to produce each possible phenotype?
c. Assign symbols to these alleles and list possible genotypes that give rise to the medium red and light red phenotypes.
d. Predict the outcome of the F1 and F2 generations in a cross between a true-breeding medium red plant and a white plant.

In 1959, doctors began using the powerful antibiotic methicillin to treat infections of staphylococcus aureus, but within two years, methicillin-resistant strains of s. aureus (mrsa) appeared. how did the resistant strains of s. aureus emerge? in 1959, doctors began using the powerful antibiotic methicillin to treat infections of staphylococcus aureus, but within two years, methicillin-resistant strains of s. aureus (mrsa) appeared. how did the resistant strains of s. aureus emerge? staphylococcus aureus bacteria that were able to synthesize cell walls using a protein that was not affected by methicillin survived the methicillin treatments and reproduced at higher rates than did other individuals. over time, these resistant individuals became increasingly common. in response to treatment of staphylococcus aureus infections with methicillin, some bacteria began to synthesize cell walls using a protein that was not affected by methicillin. these bacteria survived the methicillin treatments and reproduced at higher rates than did other individuals. over time, these resistant individuals became increasingly common. in response to treatment of staphylococcus aureus infections with methicillin, bacterial populations gradually began to synthesize cell walls using a protein that was not affected by methicillin.