<span> purines: adenine, guanine
pyrimidines: thymine, cytosine, uracil </span>
Answer:
F-: StrR, his+ and met+
Explanation:
the strain Hfr is a high-frequency strain of recombination that includes the F plasmid (fertility factor). Therefore, the whole genome sequence is able to be passed via Hfr to its receiver, but it needs a long duration of physical contact with the recipient because the recipient gets a gene (long time physical contact is seldom attained) and retains the F strain. Also, genomes from the F-cells are not passed backwards to the HF cells. Therefore, only F strain with tolerance to Streptomycin and capable of synthesizing its amino acids on limited media can thrive in this situation. Which is F-: StrR, his+ and met+ recombining.
Pasteur reasoned the factor that made the bacteria less deadly was exposure to oxygen. The discovery of the chicken cholera vaccine by Louis Pasteur revolutionized work in infectious diseases and can be considered the birth of immunology.
