Actinomycin D is an antibiotic drug that inhibits protien synthesis by blocking transcription. In some cells, the application of the drug does not affect the synthesis of certain protiens. Which of the following best explains such an occurrence?
a)Not al protiens need tRNA molecules for their syntehsis
b)The protiens that are made are using mRNA synthesized before application of the drug.
c)Nuclear protiens do not require the cytoplasmic machinery of ribosomes
d)DNA transcription is not necessary for protien synthesis.

B

Explanation:

B: Since the drug inhibits transcription, only the mRNA that have already been transcribed can go on to be translated into the protein.

A: All proteins need Transfer RNA in order to be made.

C: Nuclear proteins are first made in the cytoplasm by ribosomes and then transported back to the nucleus via the nuclear pore complex.

D: Transcription is necessary for protein synthesis. This step cannot be skipped. Otherwise, no mRNA is made and translation cannot  occur.

answer : haversian

[explanation: -(compact bone is organized as parallel columns, known as haversian systems, which run lengthwise down the axis of long bones. these columns are composed of lamellae, concentric rings of bone, surrounding a central channel, or haversian canal, that contains the nerves, blood vessels, and lymphatic system of the bone)]