The GenBank record of the HBB gene also contains this inform

The GenBank record of the HBB gene also contains this information: mRNA join (1 ... 142, 273 .. 495, 1346 .. 1606)/gene = \"HBB\"/gene_synonym = \"beta-globin; CD113t-C\"/product = \"haemoglobin, beta\"/transcript_id = \"NM_000518.4\"/db_xref = \"GI: 282302128\"/db_xref = \"GeneID: 3043\"/db_xref = \"HGNC: 4827\"/db_xref = \"MIM: 141900\" This is the actual recipe for organizing the mature mRNA that will be translated into a protein In addition, there are other pieces of information in this field: the gene name (HBB), gene (\"beta globin, CD113t-C\"), the gene product (hemoglobin, beta), and ID links to The top line shows exactly which nucleotide segments need to be joined mature mRNA. According to the instructions, there are three exons in this mRNA.

Solution

There are two introns between the exons and their 143.....272 (exon finished at 142 then intron will start at 143) and 496......1345 exon finished at 495 then intron will start at 496).

exons are the coding sequence and introns (noncoding sequence) are removed by splicing.