1. Transcription:
* DNA serves as a template for the synthesis of mRNA.
* The enzyme RNA polymerase binds to the DNA and reads the genetic code.
* RNA polymerase creates a complementary copy of the DNA sequence, replacing thymine (T) with uracil (U).
2. mRNA Processing:
* The newly synthesized mRNA undergoes processing:
* Capping: A modified guanine nucleotide is added to the 5' end.
* Splicing: Non-coding sequences (introns) are removed, and the remaining coding sequences (exons) are joined together.
* Polyadenylation: A tail of adenine nucleotides is added to the 3' end.
3. Export:
* The processed mRNA is transported out of the nucleus through nuclear pores. These are channels in the nuclear membrane that allow specific molecules to pass through.
4. Translation:
* Once in the cytoplasm, the mRNA interacts with ribosomes.
* Ribosomes read the mRNA sequence and translate it into a chain of amino acids, forming a protein.
In summary:
DNA's information is not transported directly out of the nucleus. Instead, it is copied into mRNA, which is then processed and exported. mRNA carries the genetic code to the ribosomes where it is translated into a protein. This process ensures that the DNA, the cell's blueprint, remains safe and protected within the nucleus, while copies of its information can be used to build the proteins necessary for cellular function.
