Question

what are the roles of rna molecules during the step labeled with an x in the diagram?
a. mrna: contains a copy of the lactase gene; rrna: folds the amino - acid chain to produce the lactase molecule; trna: forms peptide bonds between amino acids needed in lactase
b. mrna: provides amino acids to make lactase; rrna: makes up the ribosome, which synthesizes lactase; trna: carries nucleotides to the mrna copy of the lactase gene
c. mrna: forms peptide bonds between amino acids; rrna: produces amino acids when an mrna transcript is read; trna: carries nucleotides needed to synthesize lactase
d. mrna: carries information of lactase; rrna: makes up part of the ribosome, which decodes mrna; trna: carries amino acids to the growing lactase molecule

Explanation:

mRNA (messenger RNA) carries the genetic information from DNA to the ribosome to make proteins. rRNA (ribosomal RNA) is a component of ribosomes, which are the sites of protein - synthesis. tRNA (transfer RNA) brings amino acids to the ribosome according to the codons on the mRNA. Option B correctly describes the roles of mRNA, rRNA, and tRNA. mRNA provides instructions for making proteins, rRNA makes up part of the ribosome which synthesizes proteins, and tRNA carries amino acids to the mRNA copy of the gene.

Answer:

B. mRNA: provides instructions to make proteins; rRNA: makes up part of ribosomes which synthesize proteins; tRNA: carries amino acids to the mRNA copy of the gene