Answer:
The correct answer is ii and iii: ii. The Shine-Delgarno site in the mRNA must be accessible iii. The start codon in the mRNA must be accessible
Explanation:
In protein synthesis, the first step is to synthesize messenger RNA, mRNA. The coping process of the DNA section for the desired protein is called transcription, and it happens in the nucleus. After that, it occurs translation, when the formed mRNA moves to the cytoplasm through the nucleus membrane pores. Protein synthesis is initiated in the cytoplasm when mRNA meets a free ribosome, the primary structure for protein synthesis.
During translation, mRNAs are read in the 5´ to 3´ direction, and tRNA transfer the correct amino acids to build the polypeptide chain. The protein is then synthesized from the amino terminus to the carboxy terminus. Each amino acid is specified by a codon formed by three bases in the mRNA. mARNs have a start and end codon that tells the ribosome where to start and stop adding amino acids. When the ribosome reaches the end codon, it means that protein synthesis is finished.
There are different phases in the translation process. The initiation, the elongation, and termination. During the initiation phase, in prokaryotes, an initiation site is needed to start the translation. This site is known as the Shine-Delgarno site, and it is needed to place the ribosome over the codon. These initiation codons are preceded by the Shine-Delgarno.
In eukaryote cells, the ribosome recognizes the codon with the help of initiation factors. There is no sequence such as Shine-Delgarno in Eukaryotic cells.
