**30**wrote:

I am running the following command:

bwa mem -t 4 /users/person/resources/reference/hg19/genome/ucsc.hg19.fasta 160095-T_S2_L003_R1_001.fastq.gz 160095-t_s2_l003_r2_001.fastq.gz > 160095-T_S2_L003_R1_001.fastq.gz.bwa.sam

With the following bwa messages where all four orientations are being skipped:-

```
[M::bwa_idx_load_from_disk] read 0 ALT contigs
[M::process] read 546760 sequences (40000002 bp)...
[M::process] read 546534 sequences (40000140 bp)...
[M::mem_pestat] # candidate unique pairs for (FF, FR, RF, RR): (1, 1, 0, 0)
[M::mem_pestat] skip orientation FF as there are not enough pairs
[M::mem_pestat] skip orientation FR as there are not enough pairs
[M::mem_pestat] skip orientation RF as there are not enough pairs
[M::mem_pestat] skip orientation RR as there are not enough pairs
[mem_sam_pe] paired reads have different names: "NS500784:187:HHYNGAFXX:4:11401:17815:1049", "NS500784:187:HHYNGAFXX:1:11101:13503:1043"
[mem_sam_pe] paired reads have different names: "NS500784:187:HHYNGAFXX:4:11401:8106:1064", "NS500784:187:HHYNGAFXX:1:11101:4077:1043"
```

When I open the sam file it looks like this:

```
@SQ SN:chrM LN:16571
@SQ SN:chr1 LN:249250621
@SQ SN:chr2 LN:243199373
@SQ SN:chr3 LN:198022430
@SQ SN:chr4 LN:191154276
@SQ SN:chr5 LN:180915260
@SQ SN:chr6 LN:171115067
@SQ SN:chr7 LN:159138663
@SQ SN:chr8 LN:146364022
@SQ SN:chr9 LN:141213431
@SQ SN:chr10 LN:135534747
@SQ SN:chr11 LN:135006516
@SQ SN:chr12 LN:133851895
@SQ SN:chr13 LN:115169878
@SQ SN:chr14 LN:107349540
@SQ SN:chr15 LN:102531392
@SQ SN:chr16 LN:90354753
@SQ SN:chr17 LN:81195210
@SQ SN:chr18 LN:78077248
@SQ SN:chr19 LN:59128983
@SQ SN:chr20 LN:63025520
@SQ SN:chr21 LN:48129895
@SQ SN:chr22 LN:51304566
@SQ SN:chrX LN:155270560
@SQ SN:chrY LN:59373566
@SQ SN:chr1_gl000191_random LN:106433
@SQ SN:chr1_gl000192_random LN:547496
@SQ SN:chr4_ctg9_hap1 LN:590426
@SQ SN:chr4_gl000193_random LN:189789
@SQ SN:chr4_gl000194_random LN:191469
@SQ SN:chr6_apd_hap1 LN:4622290
@SQ SN:chr6_cox_hap2 LN:4795371
@SQ SN:chr6_dbb_hap3 LN:4610396
@SQ SN:chr6_mann_hap4 LN:4683263
@SQ SN:chr6_mcf_hap5 LN:4833398
@SQ SN:chr6_qbl_hap6 LN:4611984
@SQ SN:chr6_ssto_hap7 LN:4928567
@SQ SN:chr7_gl000195_random LN:182896
@SQ SN:chr8_gl000196_random LN:38914
@SQ SN:chr8_gl000197_random LN:37175
@SQ SN:chr9_gl000198_random LN:90085
@SQ SN:chr9_gl000199_random LN:169874
@SQ SN:chr9_gl000200_random LN:187035
@SQ SN:chr9_gl000201_random LN:36148
@SQ SN:chr11_gl000202_random LN:40103
@SQ SN:chr17_ctg5_hap1 LN:1680828
@SQ SN:chr17_gl000203_random LN:37498
@SQ SN:chr17_gl000204_random LN:81310
@SQ SN:chr17_gl000205_random LN:174588
@SQ SN:chr17_gl000206_random LN:41001
@SQ SN:chr18_gl000207_random LN:4262
@SQ SN:chr19_gl000208_random LN:92689
@SQ SN:chr19_gl000209_random LN:159169
@SQ SN:chr21_gl000210_random LN:27682
@SQ SN:chrUn_gl000211 LN:166566
@SQ SN:chrUn_gl000212 LN:186858
@SQ SN:chrUn_gl000213 LN:164239
@SQ SN:chrUn_gl000214 LN:137718
@SQ SN:chrUn_gl000215 LN:172545
@SQ SN:chrUn_gl000216 LN:172294
@SQ SN:chrUn_gl000217 LN:172149
@SQ SN:chrUn_gl000218 LN:161147
@SQ SN:chrUn_gl000219 LN:179198
@SQ SN:chrUn_gl000220 LN:161802
@SQ SN:chrUn_gl000221 LN:155397
@SQ SN:chrUn_gl000222 LN:186861
@SQ SN:chrUn_gl000223 LN:180455
@SQ SN:chrUn_gl000224 LN:179693
@SQ SN:chrUn_gl000225 LN:211173
@SQ SN:chrUn_gl000226 LN:15008
@SQ SN:chrUn_gl000227 LN:128374
@SQ SN:chrUn_gl000228 LN:129120
@SQ SN:chrUn_gl000229 LN:19913
@SQ SN:chrUn_gl000230 LN:43691
@SQ SN:chrUn_gl000231 LN:27386
@SQ SN:chrUn_gl000232 LN:40652
@SQ SN:chrUn_gl000233 LN:45941
@SQ SN:chrUn_gl000234 LN:40531
@SQ SN:chrUn_gl000235 LN:34474
@SQ SN:chrUn_gl000236 LN:41934
@SQ SN:chrUn_gl000237 LN:45867
@SQ SN:chrUn_gl000238 LN:39939
@SQ SN:chrUn_gl000239 LN:33824
@SQ SN:chrUn_gl000240 LN:41933
@SQ SN:chrUn_gl000241 LN:42152
@SQ SN:chrUn_gl000242 LN:43523
@SQ SN:chrUn_gl000243 LN:43341
@SQ SN:chrUn_gl000244 LN:39929
@SQ SN:chrUn_gl000245 LN:36651
@SQ SN:chrUn_gl000246 LN:38154
@SQ SN:chrUn_gl000247 LN:36422
@SQ SN:chrUn_gl000248 LN:39786
@SQ SN:chrUn_gl000249 LN:38502
@PG ID:bwa PN:bwa VN:0.7.15-r1140 CL:bwa/users/person/resources/reference/hg19/genome/ucsc.hg19.fasta 160095-T_S2_L004_R1_001.fastq.gz 160095-t_s2_l003_r2_001.fastq.gz
```

**BUT** when I use samtools to convert it to a bam file it's empty!

Can anyone advise?

My guess is that your paired files are not properly paired. The names of your reads don't seem to match between your pairs.

6.6kI get this error from read1 and 2 from lane 3 and 4 of this sample. all my other samples were fine. so I also thought something similar - so I tried all alignment combinations of read1 and 2 from the different lanes with the same problem - I also tried concatenation read1s from lane 3 and 4 and aligned this with read2s from lane 3 and 4.

is there a way to fix the different names of the reads?

30How to fix it? Find the right pairs.

6.6kWhat does fastqc / multiqc look like? Any major flags? Is it possible that your forward / reverse reads are randomly sorted?

5.6kfastqc was fine - no flags. this is a problem with read 1 and read 2 from lane 3 and 4 of this sample. I have 29, and this is the only one with this problem

30