Pandemic disease is
Answer: C
Correct answer: spreads through many areas of the world involving many persons within a short period
A pandemic is an epidemic that has crossed countries or continents, affecting very large numbers in a short time - influenza in 1918 and COVID-19 are the standard examples. The difference from an epidemic is one of geographical extent, not of severity.
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Reinfection is
Answer: B
Correct answer: subsequent infection by the same organism
Reinfection is a later infection by the same organism, after the first has resolved. It is distinct from a relapse, in which the original infection was never cleared and flares up again.
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Reduction of virulence is known as
Answer: A
Correct answer: attenuation
Attenuation is the reduction of virulence while the organism is kept alive - achieved by repeated subculture, growth under unfavourable conditions, or passage through an unnatural host. It is the basis of live vaccines such as BCG. The opposite, enhancing virulence by passage through a susceptible host, is called exaltation.
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Transcription is the process by which
Answer: B
Correct answer: genetic information carried in the bacterial DNA is transferred to m-RNA
Transcription is DNA to RNA: RNA polymerase reads one strand of the gene and builds a complementary messenger RNA. Making protein from that message is translation; copying DNA to DNA is replication; and RNA to DNA is reverse transcription.
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A gene is a
Answer: A
Correct answer: segment of DNA carrying codons specifying for a particular polypeptide
A gene is a stretch of DNA whose sequence of codons specifies one polypeptide (or one functional RNA). A single triplet is a codon, not a gene, and it specifies one amino acid.
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Transformation is
Answer: A
Correct answer: the transfer of genetic information through the agency of free DNA
Transformation is the uptake of naked DNA from the surroundings by a competent cell - the phenomenon Griffith observed in 1928 and Avery explained in 1944, and the one that identified DNA as the genetic material. The alternatives describe the other two mechanisms of bacterial gene transfer: transduction, by a bacteriophage, and conjugation, by cell-to-cell contact.
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