In the first section of this course, we discussed an experiment performed by Fre

Question

In the first section of this course, we discussed an experiment performed by Frederick Griffiths in 1928 with two strains of Pneumococcus bacteria, called the Smooth strain and the Rough strain. The Smooth strain was the wild-type strain. It formed a smooth polysaccharide coat which enabled it to be infectious in mice. The Rough strain was a spontaneous mutant that arose when Griffith was growing the Smooth strain on agar plates. The Rough strain could not make the polysaccharide coat due to a mutation in the coat gene called C, and as a result, it was not infectious in mice. A mutant allele of C, called C^R, results in the Rough strain because it results in a failure of the bacteria to make a polysaccharide coat. As you may recall, Griffith's exciting observation was that he could convert the R strain to the S strain by mixing R strain bacteria with heat-killed S strain bacteria. in essence, Griffith had "transformed" the R strain with a wild-type copy of the C gene from the S strain, called C^s. Bacteria are normally haploid. However, in the transformation experiment, the R-strain bacteria ended up with a second copy of the C gene: they had both the C^R allele and the C^s allele. Which allele of C is dominant in regard to the ability of bacteria to make the polysaccharide coat? Circle: C^R or C%s Explain in one sentence the data (from the description above) that supports your answer. Is C^R likely to be a dominant-negative mutation? Circle Yes or No. Explain in one sentence the data (from the description above) that supports your answer.

Explanation / Answer

The Cs allele is dominant in its capacity to transform the live Cr strain into Cs strain that makes it virulent. B. Cr is not a dominant negative strain as this allele is expressed only in the absence of Cs i.e. smooth allele, i.e. in homozygous condition

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