Hello Everyone. I am working with the sra data for whole exome sequence analysis. I am facing a problem regarding the sam file that I created after alignment. I am adding all the steps.

fastq-dump --split-files SRR1178899.sra

*fastqc *.fq*

bwa mem -t 12 -Y -L 0 -M -R "@RG\tID:sample\tSM:sample\tPL:Illumina" /mnt/nas/reference_genome/BWA/mammals/hg38/genome.fa R1_step1.fq R2_step1.fq > aligned_reads.sam

after this, when I check,

samtools quickcheck aligned_reads.sam

aligned_reads.sam was not identified as sequence data.

samtools view -H aligned_reads.sam

[main_samview] fail to read the header from "aligned_reads.sam".

less aligned_reads.sam

    @SQ     SN:chrUn_KI270363v1     LN:1803
    @SQ     SN:chrUn_KI270364v1     LN:2855
    @SQ     SN:chrUn_KI270362v1     LN:3530
    @SQ     SN:chrUn_KI270366v1     LN:8320
    @SQ     SN:chrUn_KI270378v1     LN:1048
    @SQ     SN:chrUn_KI270379v1     LN:1045
    @SQ     SN:chrUn_KI270389v1     LN:1298
    @SQ     SN:chrUn_KI270390v1     LN:2387
    @SQ     SN:chrUn_KI270387v1     LN:1537
    @SQ     SN:chrUn_KI270395v1     LN:1143
    @SQ     SN:chrUn_KI270396v1     LN:1880
    @SQ     SN:chrUn_KI270388v1     LN:1216
    @SQ     SN:chrUn_KI270394v1     LN:970
    @SQ     SN:chrUn_KI270386v1     LN:1788
    @SQ     SN:chrUn_KI270391v1     LN:1484
    @SQ     SN:chrUn_KI270383v1     LN:1750
    @SQ     SN:chrUn_KI270393v1     LN:1308
    @SQ     SN:chrUn_KI270384v1     LN:1658
    @SQ     SN:chrUn_KI270392v1     LN:971
    @SQ     SN:chrUn_KI270381v1     LN:1930
    @SQ     SN:chrUn_KI270385v1     LN:990
    @SQ     SN:chrUn_KI270382v1     LN:4215
    @SQ     SN:chrUn_KI270376v1     LN:1136
    @SQ     SN:chrUn_KI270374v1     LN:2656
    @SQ     SN:chrUn_KI270372v1     LN:1650
    @SQ     SN:chrUn_KI270373v1     LN:1451
    @SQ     SN:chrUn_KI270375v1     LN:2378
    @SQ     SN:chrUn_KI270371v1     LN:2805
    @SQ     SN:chrUn_KI270448v1     LN:7992
    @SQ     SN:chrUn_KI270521v1     LN:7642
    @SQ     SN:chrUn_GL000195v1     LN:182896
    @SQ     SN:chrUn_GL000219v1     LN:179198
    @SQ     SN:chrUn_GL000220v1     LN:161802
    @SQ     SN:chrUn_GL000224v1     LN:179693
    @SQ     SN:chrUn_KI270741v1     LN:157432
    @SQ     SN:chrUn_GL000226v1     LN:15008
    @SQ     SN:chrUn_GL000213v1     LN:164239
    @SQ     SN:chrUn_KI270743v1     LN:210658
    @SQ     SN:chrUn_KI270744v1     LN:168472
    @SQ     SN:chrUn_KI270745v1     LN:41891
    @SQ     SN:chrUn_KI270746v1     LN:66486
    @SQ     SN:chrUn_KI270747v1     LN:198735
    @SQ     SN:chrUn_KI270748v1     LN:93321
    @SQ     SN:chrUn_KI270749v1     LN:158759
    @SQ     SN:chrUn_KI270750v1     LN:148850
    @SQ     SN:chrUn_KI270751v1     LN:150742
    @SQ     SN:chrUn_KI270752v1     LN:27745
    @SQ     SN:chrUn_KI270753v1     LN:62944
    @SQ     SN:chrUn_KI270754v1     LN:40191
    @SQ     SN:chrUn_KI270755v1     LN:36723
    @SQ     SN:chrUn_KI270756v1     LN:79590
    @SQ     SN:chrUn_KI270757v1     LN:71251
    @SQ     SN:chrUn_GL000214v1     LN:137718
    @SQ     SN:chrUn_KI270742v1     LN:186739
    @SQ     SN:chrUn_GL000216v2     LN:176608
    @SQ     SN:chrUn_GL000218v1     LN:161147
    @SQ     SN:chrEBV       LN:171823
    @PG     ID:bwa  PN:bwa  VN:0.7.17-r1188 CL:bwa mem -t 12 -M /mnt/nas/reference_genome/BWA/mammals/hg38/genome.fa R1_step1.fq R2_step1.fq
    SRR1178899.1    77      *       0       0       *       *       0       0       TNGTTCCAGCGACAGCCCATCCTATAGCACTCTCCAGGAGAGAAATCCAGCACACAAAAAAGATTCTACATCTATTAAGTAAGTGAGGTCTGAGTTGGAT    =#14:ADD=D@FFGCGHIIAHHGGGDC@DHC?::BGFHG;?(?FH>4.8))7=8(5-=?AB#######################################    AS:i:0  XS:i:0
    SRR1178899.1    141     *       0       0       *       *       0       0       ACATATATTGGAAACTACAACACTATGGGGAAGAGAACCAATTCAGAACTCAATAACTTAATAGAAGGAGAAGCTTTTTGATGTACTATATTTCTCTCCA    ####################################################################################################    AS:i:0  XS:i:0
    SRR1178899.2    77      *       0       0       *       *       0       0       TNTTTCCAGCGACAGCCCATCCTATAGCACTCTCCAGGAGAGAAATTTAGTACACAATAAGGAGACCCCTCGTCTTAAGTGCGGTCGGTAAGAGTCGGAT    <#144ADDDDDDDIIIIIIIIIIIIIIIIIIIIIIIIIDIDIDIIIICIICEEICC############################################    AS:i:0  XS:i:0
    SRR1178899.2    141     *       0       0       *       *       0       0       AGGATTTAAATAGGCGCTCGGGGTCTGCAATAGCCCCCAGCTGCGTGGTAAATCTGCCTCACGGAGTGTCCTGTAGGATTGGCTACTACGGGGAACGCAG    ####################################################################################################    AS:i:0  XS:i:0
    SRR1178899.3    83      chr12   94582927        60      45M55S  =       94582829        -143    ATCCAACTCAGAACTCACTCACTTAATAGAAGGAGAATCTTTTTTGTGTACTAAATTTCTCTCCTGGAGAGTGCTATAGGATGGGCTGTCGCTGGATGNA    ###DDDCCA@:;5@A:ACCC;:B>-C>33CCECC>C@EDFGIGGGIHHEDJIIGHJHGGD=FEGFGIFIIJHEDCGFJJIHGHFE@GHFCFAFFDDA1#@    NM:i:0  MD:Z:45 MC:Z:100M       AS:i:45 XS:i:0
    SRR1178899.3    163     chr12   94582829        60      100M    =       94582927        143     ATGAGGTCACCAGTCAGTCCCGGTCTCCCAAAGTGCCCAGGTAACTGGAATGCCTGCCATGCCACATTCACTGGGAACTTCACCACTATGGGGAACGCAT    @@BFFFFFFHHBCAFE@EICFFG@GFCHGHGID?BFGGIJIFDFGEHEFFGHEHIJJJIJJIIEHHHHHHHF>B?BEDDECECDDBCDDD>ABDBDBB@B    NM:i:1  MD:Z:60A39      MC:Z:45M55S     AS:i:95 XS:i:20
    SRR1178899.4    83      chr1    121509428       60      46M54S  =       121509376       -98     ATGCCCAACAATGACAGACTGAATAAAGAAATTGTGCTACATATATGTGTACTAAGTTTCTCTCCTGGAGAGTGCTATAGGAGGGCTGTCGCTGGAGCNC    9528?<CA:(55(A@;(>>;@@A;.;7););6..7A?==HDC;@=)..///8.=B8>EGEHHBFD?*FGFB9B<F>HAHGHFE;BG@AFFAA:DBA41#?    NM:i:0  MD:Z:46 MC:Z:98M2S      AS:i:46 XS:i:30
    SRR1178899.4    163     chr1    121509376       60      98M2S   =       121509428       98      AAATGTTTACTGCAACATTATTCATGATAGCAAAGATATGAAATCAACCTAAATGCCCAACAATGACAGACTGAATAAAGAAATTGTGCTACATATATGT    @@@DFDDFFFHHHC@<:CC?IHCBHHIICH???DFCGGIIIGIIDAC??D:BAFH@?F?DDBEHGGF

So, I create a header.txt file for hg38 genome which is my reference genome.

@HD VN:1.6  SO:coordinate
@SQ SN:chr1 LN:248956422
@SQ SN:chr2 LN:242193529
@SQ SN:chr3 LN:198295559
@SQ SN:chr4 LN:190214555
@SQ SN:chr5 LN:181538259
@SQ SN:chr6 LN:170805979
@SQ SN:chr7 LN:159345973
@SQ SN:chr8 LN:145138636
@SQ SN:chr9 LN:138394717
@SQ SN:chr10    LN:133797422
@SQ SN:chr11    LN:135086622
@SQ SN:chr12    LN:133275309
@SQ SN:chr13    LN:114364328
@SQ SN:chr14    LN:107043718
@SQ SN:chr15    LN:101991189
@SQ SN:chr16    LN:90338345
@SQ SN:chr17    LN:83257441
@SQ SN:chr18    LN:80373285
@SQ SN:chr19    LN:58617616
@SQ SN:chr20    LN:64444167
@SQ SN:chr21    LN:46709983
@SQ SN:chr22    LN:50818468
@SQ SN:chrX LN:156040895
@SQ SN:chrY LN:57227415
@SQ SN:chrM LN:16569

cat header.txt aligned_reads.sam > aligned_header.sam
samtools quickcheck aligned_header.sam
align_header.sam was not identified as sequence data.

Can you please help in this case? It is very urgent. Thank you in advance.

I can provide more information if you need.