Video Transcript
The amino acid alanine can be coded
for by the codons GCU, GCC, GCA, or GCG. What feature of the genetic code is
this an example of? (A) It is universal. (B) It is nonoverlapping. (C) It is specific for each
organism. (D) It is degenerate. (E) It contains no repeated
codons.
In order for a gene in DNA to be
converted into a protein, it needs to go through two steps. First, the DNA sequence is
converted into mRNA during a process called transcription. Then the sequence in mRNA is
converted into a sequence of amino acids to form the protein. Let’s look at how a sequence of
mRNA can be translated into amino acids.
A group of three nucleotides in
mRNA is called a codon. In this nine-nucleotide sequence of
mRNA, there’s three codons. The specific sequence in a codon
corresponds to a specific amino acid. The sequence GCU corresponds to the
amino acid alanine. How these codons are converted into
amino acids is given by the genetic code. Here, we can see a codon wheel that
gives the different combinations of nucleotides in codons and the corresponding
amino acid.
The codon GCU corresponds to the
amino acid alanine. We can also see that the codons
GCC, GCA, and GCG also correspond to the amino acid alanine. Four different codons can all code
for the same amino acid. The genetic code is redundant, or
degenerate, meaning that more than one codon can code for a specific amino acid.
Therefore, the correct answer is
answer choice (D). It is degenerate.
