Some viruses can be crystallized and their structures analyzed. One such virus i

Question

Some viruses can be crystallized and their structures analyzed. One such virus is Desmodium, or yellow mottle virus, which infects beans. This is a member of the tymovirus group and has a single-stranded RNA genome of ~6,300 nucleotides. Its virion is 25—30 nm in diameter, and is made up of 180 copies of a single capsid protein that self-associate to form each capsomere, which has icosahedral symmetry with 20 facets.

1) If this virus has capsomeres with 20 facets, how many proteins form each one?A) 1 B) 5 C) ~6 D) ~20 E) ~180

2) How many nucleotides of the genome would you expect to find in one capsid? A) 1 B) ~6 C) ~20 D) ~180 E) ~6,300

3) If this virus has a positive RNA strand as its genome, it begins the infection by using this strand as mRNA. Therefore, which of the following do you expect to be able to measure? A) replication rate B) transcription rate C) translation rate D) accumulation of new ribosomes E) formation of new transcription factors

4) In a cell-free system, what other components would you have to provide for this virus to express its genes? A) ribosomes, tRNAs and amino acids B) ribosomes, tRNAs, amino acids, and GTP C) RNA nucleotides and GTP D) RNA nucleotides, RNA polymerase, and GTP E) bean cell enzymes

Explanation / Answer

1) If this virus has capsomeres with 20 facets, then the number of protein form each capsomere is ~180.

2) ~6,300 nucleotides is found to be associated with one capsid.

3) Transcription would be able to measure the concerned.

4) In a cell-free system, components required by virus to express its genes include ribosomes, tRNAs, amino acids, and GTP.

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