If one part of the DNA molecule looked like ATGGCT, what would the protein look like?
The DNA sequence ATGGCT must first be transcribed into messenger RNA (mRNA). This occurs during a process called transcription.
Transcription occurs in the nucleus of the cell. The strands of the DNA molecule are separated by an enzyme called helicase. Another enzyme called RNA polymerase reads the sequence of the DNA strand and creates a single stranded RNA molecule containing bases that are complementary to the bases in the DNA strand. The nucleotide bases that are found in RNA are: adenine, uracil, cytosine, and guanine.
- Adenine is complementary to thymine.
- Uracil is complementary to adenine.
- Cytosine is complementary to guanine.
- Guanine is complementary to cytosine.
Therefore, the mRNA sequence that is complementary to the DNA sequence ATGGCT would be UACCGA.
The mRNA strand is then transported into the cytoplasm where it undergoes a process called translation. A protein structure called a ribosome uses transfer RNA strands to attach together amino acids that are coded for by the mRNA sequence. Amino acids are the building blocks of proteins.
Within the mRNA sequence, every three bases codes for a particular amino acid. Each three base sequence in the mRNA is called a codon. You can find a chart that shows the codon code for each amino acid online or in your textbook.
The codon sequence UAC, is the code for the amino acid tyrosine. The codon sequence CGA, is the code for the amino acid arginine. Therefore, a protein that resulted from the DNA sequence ATGGCT be composed of the amino acid tyrosine joined with the amino acid arginine.