14 lines (10 with data), 380 Bytes

>chrM
GATCACAGGTCTATCACCCTATTaaCCACTCACGGGAGCTCTCCATGCAT
TTGGTATTTTCGTCTGGGGGGTGTGCACGCGATAGCATTGCGAGACGCTG

>chr1 single_word_description
ACCACCATCCTCCGTGAAATCAATATCCCGCACAAGAGTGCTACTCTCCT
AAATCCCTTCTCGTCCCCATGGATGA


>chr2 multi-word description is here
CGCTNCGGGCCCATAACACTTGGGGGTAGCTAAAGTGAACTGTATCCGAC
ATCTGGTTCCTACTTCAGGGCCATAAAGCCTAAATAGCCCACACGTTCCC
CTTAAATAAGACATCACGATG