Question: Phasing without a reference panel
0
gravatar for chadapohn.chaosrikul
3.1 years ago by
chadapohn.chaosrikul0 wrote:

Hi all,

I'm trying to make my own cohort from genotypes like HapMap project. I would like to know if there are any phasing tools which contain options for phasing genotypes when there's no reference panel?

Thank you.

ADD COMMENTlink modified 3.1 years ago by Wietje220 • written 3.1 years ago by chadapohn.chaosrikul0
2
gravatar for Wietje
3.1 years ago by
Wietje220
Germany
Wietje220 wrote:

Beagle 4.0 offers the option to impute and phase without a reference panel

You should be able to run it with: java -jar ./beagle gt=[your.file.vcf] phase-its=5 nthreads=1 out=[your.output]

You can speed up the process with more threads and improve phasing accuracy by augmenting the phase-its number.

Documentation can be found here: https://faculty.washington.edu/browning/beagle/beagle.29Sep14.pdf

ADD COMMENTlink modified 3.1 years ago • written 3.1 years ago by Wietje220
1

And you might want to take a look at SHAPEIT as well (http://mathgen.stats.ox.ac.uk/genetics_software/shapeit/shapeit.html)...

ADD REPLYlink written 3.1 years ago by Wietje220

Thank you for your help! I'd like to know if I used SHAPEIT without a reference (by not specify --input-ref option) Does it use the default reference e.g 1000GP or use MCMC algorithm to estimate haplotypes instead?

ADD REPLYlink modified 3.0 years ago • written 3.0 years ago by chadapohn.chaosrikul0
1

As far as I know, you have to invoke the reference panel option with --input-ref to make use of such a panel - otherwise SHAPEIT will phase without this kind of background information. If you want to use the 1000GP data for your phasing step, you'd have to download it as described on the SHAPEIT page (also check these instructions for further parameters and input/output options:

https://mathgen.stats.ox.ac.uk/genetics_software/shapeit/shapeit.html#prephasing

ADD REPLYlink written 3.0 years ago by Wietje220

I've already tried both Beagle and SHAPEIT. Thank you for your suggestions.

ADD REPLYlink modified 3.0 years ago • written 3.0 years ago by chadapohn.chaosrikul0
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