This code system http://hl7.org/fhir/sequence-type defines the following codes:

CodeDisplayDefinition
aa AA SequenceAmino acid sequence.
dna DNA SequenceDNA Sequence.
rna RNA SequenceRNA Sequence.
<status value="active"/><experimental value="false"/><date value="2021-01-05T10:01:24+11:00"/><publisher value="HL7 (FHIR Project)"/><contact><telecom><system value="url"/><value value="http://hl7.org/fhir"/></telecom><telecom><system value="email"/><value value="fhir@lists.hl7.org"/></telecom></contact><description value="Type if a sequence -- DNA, RNA, or amino acid sequence."/><jurisdiction><coding><system value="http://unstats.un.org/unsd/methods/m49/m49.htm"/><code value="001"/><display value="World"/></coding></jurisdiction><caseSensitive value="true"/><valueSet value="http://hl7.org/fhir/ValueSet/sequence-type"/><content value="complete"/><concept><code value="aa"/><display value="AA Sequence"/><definition value="Amino acid sequence."/></concept><concept><code value="dna"/><display value="DNA Sequence"/><definition value="DNA Sequence."/></concept><concept><code value="rna"/><display value="RNA Sequence"/><definition value="RNA Sequence."/></concept></CodeSystem>