Jennifer L. answered • 10/14/19
Expert Librarian Specializing in Biology, Medicine, Research & Writing
The nucleus of a eukaryotic cell, such as a human cell, contains the DNA which forms the genetic blueprint for life. DNA consists of long strings of matched pairs of four chemical building blocks called bases: thymine (T), cytosine (C), guanine (G) and adenine (A). In DNA, A always matches to T and C always matches to G. The sequence of these A,T, G, C bases in the DNA strands forms a complex code for the creation of RNA and protein molecules though the processes of transcription and translation. Transcription involves opening up the DNA and copying one strand of it into an RNA string, using the base matching rules, albeit with a substitution of a base called uracil (U) in RNA for the T in DNA. RNA strings can have multiple functions, but a very important one is to be 'messenger' for the creation of proteins; these are called mRNAs. Once the transcription process is done, the mRNA is processed and transferred from the nucleus to the cytoplasm of the cell. There is it used by large chemical machines called ribosomes along with another type of RNA, transfer RNA (tRNA), to create specific protein sequences in a process called translation. During translation, each tRNA matches a specific triplet of bases with its corresponding sequence in the mRNA, using the base-matching rules (A-U and C-G). Once matched to the mRNA, the tRNA releases the unique amino acid it is carrying and the ribosome adds it to the growing protein chain. Translation ends when the protein molecule is complete. Normally, this process works perfectly, but if there is accidental damage to the sequence of the DNA bases, even a single base-pair change, the mutation of the code can cause problems anywhere in the transcription and translation processes, resulting in the inability to make a protein or the creation of a dysfunctional one. Such mutations are often, although not always, associated with cell dysfunction and disease.
