During protein synthesis, the molecule that remains in the nucleus is DNA. DNA contains the genetic instructions used in the development and functioning of all known living organisms. Here’s a brief explanation of the process:
1. Transcription: The first step of protein synthesis occurs in the nucleus. During transcription, a specific segment of DNA is copied into messenger RNA (mRNA) by the enzyme RNA polymerase. This mRNA carries the genetic information from the DNA to the ribosomes, where protein synthesis occurs.
2. mRNA Processing: Before the mRNA leaves the nucleus, it undergoes processing. This includes the addition of a 5′ cap and a poly-A tail, as well as the removal of introns (non-coding regions) through splicing. The processed mRNA is then transported out of the nucleus to the cytoplasm.
3. Translation: In the cytoplasm, the mRNA is translated into a protein by ribosomes. Transfer RNA (tRNA) molecules bring amino acids to the ribosome, where they are added to the growing polypeptide chain according to the sequence of codons on the mRNA.
Throughout this entire process, the DNA remains in the nucleus. It serves as the permanent storage of genetic information and is not transported out of the nucleus. The mRNA, on the other hand, acts as a temporary copy of the genetic information and is the molecule that moves between the nucleus and the cytoplasm to facilitate protein synthesis.