To Whom It May Concern,

How do the BLAT and Self-Chain algorithms differ? The reason I ask is shown 
below.
In trying to look at differences among the MHC haplotypes, I did a BLAT search 
on the following sequence:

>seq1
ACAGACCCCAGCTTTACAAGGACCCCAGCTCCTTAACACAGATCCCAGCTCCGAGGAAACTCGTCCCCCCCACGTTAATCCTGACCGACTTTGCCACATG
BLAT Search Results

   ACTIONS      QUERY           SCORE START  END QSIZE IDENTITY CHRO STRAND  
START    END      SPAN
---------------------------------------------------------------------------------------------------
browser<http://genome.ucsc.edu/cgi-bin/hgTracks?position=chr6_mann_hap4:2454805-2454904&db=hg19&ss=../trash/hgSs/hgSs_genome_a22_b1d170.pslx+../trash/hgSs/hgSs_genome_a22_b1d170.fa&hgsid=185182739>
 
details<http://genome.ucsc.edu/cgi-bin/hgc?o=2454804&g=htcUserAli&i=../trash/hgSs/hgSs_genome_a22_b1d170.pslx+..%2Ftrash%2FhgSs%2FhgSs_genome_a22_b1d170.fa+YourSeq&c=chr6_mann_hap4&l=2454804&r=2454904&db=hg19&hgsid=185182739>
 YourSeq          100     1   100   100 100.0%  6_mann_hap4   +    2454805   
2454904    100
browser<http://genome.ucsc.edu/cgi-bin/hgTracks?position=chr6_dbb_hap3:2403575-2403674&db=hg19&ss=../trash/hgSs/hgSs_genome_a22_b1d170.pslx+../trash/hgSs/hgSs_genome_a22_b1d170.fa&hgsid=185182739>
 
details<http://genome.ucsc.edu/cgi-bin/hgc?o=2403574&g=htcUserAli&i=../trash/hgSs/hgSs_genome_a22_b1d170.pslx+..%2Ftrash%2FhgSs%2FhgSs_genome_a22_b1d170.fa+YourSeq&c=chr6_dbb_hap3&l=2403574&r=2403674&db=hg19&hgsid=185182739>
 YourSeq          100     1   100   100 100.0%  6_dbb_hap3   +    2403575   
2403674    100
browser<http://genome.ucsc.edu/cgi-bin/hgTracks?position=chr6_cox_hap2:2621159-2621258&db=hg19&ss=../trash/hgSs/hgSs_genome_a22_b1d170.pslx+../trash/hgSs/hgSs_genome_a22_b1d170.fa&hgsid=185182739>
 
details<http://genome.ucsc.edu/cgi-bin/hgc?o=2621158&g=htcUserAli&i=../trash/hgSs/hgSs_genome_a22_b1d170.pslx+..%2Ftrash%2FhgSs%2FhgSs_genome_a22_b1d170.fa+YourSeq&c=chr6_cox_hap2&l=2621158&r=2621258&db=hg19&hgsid=185182739>
 YourSeq          100     1   100   100 100.0%  6_cox_hap2   +    2621159   
2621258    100
browser<http://genome.ucsc.edu/cgi-bin/hgTracks?position=chr6:31106437-31106536&db=hg19&ss=../trash/hgSs/hgSs_genome_a22_b1d170.pslx+../trash/hgSs/hgSs_genome_a22_b1d170.fa&hgsid=185182739>
 
details<http://genome.ucsc.edu/cgi-bin/hgc?o=31106436&g=htcUserAli&i=../trash/hgSs/hgSs_genome_a22_b1d170.pslx+..%2Ftrash%2FhgSs%2FhgSs_genome_a22_b1d170.fa+YourSeq&c=chr6&l=31106436&r=31106536&db=hg19&hgsid=185182739>
 YourSeq          100     1   100   100 100.0%     6   +   31106437  31106536   
 100
browser<http://genome.ucsc.edu/cgi-bin/hgTracks?position=chr6_mcf_hap5:2488382-2488481&db=hg19&ss=../trash/hgSs/hgSs_genome_a22_b1d170.pslx+../trash/hgSs/hgSs_genome_a22_b1d170.fa&hgsid=185182739>
 
details<http://genome.ucsc.edu/cgi-bin/hgc?o=2488381&g=htcUserAli&i=../trash/hgSs/hgSs_genome_a22_b1d170.pslx+..%2Ftrash%2FhgSs%2FhgSs_genome_a22_b1d170.fa+YourSeq&c=chr6_mcf_hap5&l=2488381&r=2488481&db=hg19&hgsid=185182739>
 YourSeq           98     1   100   100  99.0%  6_mcf_hap5   +    2488382   
2488481    100
browser<http://genome.ucsc.edu/cgi-bin/hgTracks?position=chr6_qbl_hap6:2402283-2402381&db=hg19&ss=../trash/hgSs/hgSs_genome_a22_b1d170.pslx+../trash/hgSs/hgSs_genome_a22_b1d170.fa&hgsid=185182739>
 
details<http://genome.ucsc.edu/cgi-bin/hgc?o=2402282&g=htcUserAli&i=../trash/hgSs/hgSs_genome_a22_b1d170.pslx+..%2Ftrash%2FhgSs%2FhgSs_genome_a22_b1d170.fa+YourSeq&c=chr6_qbl_hap6&l=2402282&r=2402381&db=hg19&hgsid=185182739>
 YourSeq           96     1   100   100  96.0%  6_qbl_hap6   +    2402283   
2402381     99
browser<http://genome.ucsc.edu/cgi-bin/hgTracks?position=chr17:8526697-8526717&db=hg19&ss=../trash/hgSs/hgSs_genome_a22_b1d170.pslx+../trash/hgSs/hgSs_genome_a22_b1d170.fa&hgsid=185182739>
 
details<http://genome.ucsc.edu/cgi-bin/hgc?o=8526696&g=htcUserAli&i=../trash/hgSs/hgSs_genome_a22_b1d170.pslx+..%2Ftrash%2FhgSs%2FhgSs_genome_a22_b1d170.fa+YourSeq&c=chr17&l=8526696&r=8526717&db=hg19&hgsid=185182739>
 YourSeq           21    22    42   100 100.0%    17   -    8526697   8526717   
  21




The MANN (6_mann_hap4) result shows a perfect alignment.
The QBL (6_qbl_hap6) result shows one polymorphism and one insertion.

Next, I did a BLAT on a subset of this sequence that includes the polymorphism 
and insertion sites:
>seq2
CCGAGGAAACTCGTCCCCCCCGTTAATCCTGACCGACTT

BLAT Search Results

   ACTIONS      QUERY           SCORE START  END QSIZE IDENTITY CHRO STRAND  
START    END      SPAN
---------------------------------------------------------------------------------------------------
browser<http://genome.ucsc.edu/cgi-bin/hgTracks?position=chr6_mann_hap4:2454855-2454895&db=hg19&ss=../trash/hgSs/hgSs_genome_1458_b24af0.pslx+../trash/hgSs/hgSs_genome_1458_b24af0.fa&hgsid=185185025>
 
details<http://genome.ucsc.edu/cgi-bin/hgc?o=2454854&g=htcUserAli&i=../trash/hgSs/hgSs_genome_1458_b24af0.pslx+..%2Ftrash%2FhgSs%2FhgSs_genome_1458_b24af0.fa+YourSeq&c=chr6_mann_hap4&l=2454854&r=2454895&db=hg19&hgsid=185185025>
 YourSeq           38     1    39    39 100.0%  6_mann_hap4   +    2454855   
2454895     41
browser<http://genome.ucsc.edu/cgi-bin/hgTracks?position=chr6_dbb_hap3:2403625-2403665&db=hg19&ss=../trash/hgSs/hgSs_genome_1458_b24af0.pslx+../trash/hgSs/hgSs_genome_1458_b24af0.fa&hgsid=185185025>
 
details<http://genome.ucsc.edu/cgi-bin/hgc?o=2403624&g=htcUserAli&i=../trash/hgSs/hgSs_genome_1458_b24af0.pslx+..%2Ftrash%2FhgSs%2FhgSs_genome_1458_b24af0.fa+YourSeq&c=chr6_dbb_hap3&l=2403624&r=2403665&db=hg19&hgsid=185185025>
 YourSeq           38     1    39    39 100.0%  6_dbb_hap3   +    2403625   
2403665     41
browser<http://genome.ucsc.edu/cgi-bin/hgTracks?position=chr6_cox_hap2:2621209-2621249&db=hg19&ss=../trash/hgSs/hgSs_genome_1458_b24af0.pslx+../trash/hgSs/hgSs_genome_1458_b24af0.fa&hgsid=185185025>
 
details<http://genome.ucsc.edu/cgi-bin/hgc?o=2621208&g=htcUserAli&i=../trash/hgSs/hgSs_genome_1458_b24af0.pslx+..%2Ftrash%2FhgSs%2FhgSs_genome_1458_b24af0.fa+YourSeq&c=chr6_cox_hap2&l=2621208&r=2621249&db=hg19&hgsid=185185025>
 YourSeq           38     1    39    39 100.0%  6_cox_hap2   +    2621209   
2621249     41
browser<http://genome.ucsc.edu/cgi-bin/hgTracks?position=chr6:31106487-31106527&db=hg19&ss=../trash/hgSs/hgSs_genome_1458_b24af0.pslx+../trash/hgSs/hgSs_genome_1458_b24af0.fa&hgsid=185185025>
 
details<http://genome.ucsc.edu/cgi-bin/hgc?o=31106486&g=htcUserAli&i=../trash/hgSs/hgSs_genome_1458_b24af0.pslx+..%2Ftrash%2FhgSs%2FhgSs_genome_1458_b24af0.fa+YourSeq&c=chr6&l=31106486&r=31106527&db=hg19&hgsid=185185025>
 YourSeq           38     1    39    39 100.0%     6   +   31106487  31106527   
  41
browser<http://genome.ucsc.edu/cgi-bin/hgTracks?position=chr6_qbl_hap6:2402333-2402372&db=hg19&ss=../trash/hgSs/hgSs_genome_1458_b24af0.pslx+../trash/hgSs/hgSs_genome_1458_b24af0.fa&hgsid=185185025>
 
details<http://genome.ucsc.edu/cgi-bin/hgc?o=2402332&g=htcUserAli&i=../trash/hgSs/hgSs_genome_1458_b24af0.pslx+..%2Ftrash%2FhgSs%2FhgSs_genome_1458_b24af0.fa+YourSeq&c=chr6_qbl_hap6&l=2402332&r=2402372&db=hg19&hgsid=185185025>
 YourSeq           36     1    39    39  97.5%  6_qbl_hap6   +    2402333   
2402372     40
browser<http://genome.ucsc.edu/cgi-bin/hgTracks?position=chr6_mcf_hap5:2488432-2488472&db=hg19&ss=../trash/hgSs/hgSs_genome_1458_b24af0.pslx+../trash/hgSs/hgSs_genome_1458_b24af0.fa&hgsid=185185025>
 
details<http://genome.ucsc.edu/cgi-bin/hgc?o=2488431&g=htcUserAli&i=../trash/hgSs/hgSs_genome_1458_b24af0.pslx+..%2Ftrash%2FhgSs%2FhgSs_genome_1458_b24af0.fa+YourSeq&c=chr6_mcf_hap5&l=2488431&r=2488472&db=hg19&hgsid=185185025>
 YourSeq           34     1    39    39  94.9%  6_mcf_hap5   +    2488432   
2488472     41


This time:

The MANN result shows me a deletion of AC.

The QBL result shows me that the polymorphism is present, but that there is a 
deletion rather than an insertion 8 bp away from the polymorphism site.

Furthermore, the Self-Chain alignment within the MANN result shows that the QBL 
has a different base deleted than the one shown in the QBL result.

Why the discrepancies?



Sincerely,

Hannah Cheung, PhD
Postdoctoral Associate
Plon Lab
1102 Bates Ave
Rm.1200.18
Texas Children's Hospital
Houston, TX 77030
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