With very rare exceptions, the semibreve is now the longest note and the minim is thirty-two times the length of the shortest.
From the newscientist.com
The relation between the breve and the semibreve was called tempus, and the relation between the semibreve and the minim was called prolatio.
From the en.wikipedia.org
So if an amino acid is loaded by the most common codon, its corresponding chord would receive the longest possible time value, a semibreve lasting four beats.
From the newscientist.com
More examples
Whole note: a musical note having the longest time value (equal to four beats in common time)
Whole note
A type of note which lasts for four beats. They are also known as whole-notes.