Describe the pathway from DNA nucleotides to proteins.
You have asked about the pathway from DNA to proteins. DNA stands for deoxyribonucleic acid and it is composed of long chains of nucleotides. These nucleotides are composed of a ribose sugar (minus one of the hydroxyl groups), a phosphate group, and one of four different nitrogen and carbon containing base groups. The sequences of these base groups are what give the genetic information to DNA.
The process of going from DNA to a complete protein is called protein biosynthesis and it is composed of two different stages. The first stage is called transcription. This is where a strand of double helix DNA (a gene) is unwound so that one side can be read by an enzyme called RNA polymerase. This enzyme builds a sequence of messenger RNA (mRNA) based on the sequence of nucleotides in the DNA. The mRNA sequence is said to be complementary since it contains the matching nucleotide bases to the DNA sequence.
The second part of the process is called translation. This is where the mRNA leaves the DNA in the nucleus and travels to a part of the cell called a ribosome. This is where the actual protein is built from individual amino acids. The nucleotides in the mRNA are read as groups of three called codons. Each codon corresponds to a particular amino acid. The ribosome reads the codons and builds the protein one amino acid at a time according to the nucleotide sequence in the mRNA. Once complete, the protein is allowed to fold to its natural shape, thus giving a completed protein which is then able to leave the ribosome and travel to wherever it is needed.