Assignment 8 Review - genetics.wustl.edu

Copying and Pasting from Stack Overflow O'REILLY' Practical Developer . I Redraw; ICO Length. 66 aa Frame from to Length +1 +3 a .200 1 .200 3..200 20...

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Assignment 8 Review Bio5488 3/31/2017

Adapted from Mayank

Don’t hesitate and ask questions early!

Longest ORFs? (1)

(2)

(3)

ORFs CONTIG#1

| ATG

| Stop

|

|

|

ATG

ATG

ATG

| Stop

| ATG

| Stop

• ORFs are mutually exclusive -> 2 ORFs in a certain frame cannot share the same start or stop codon • One possible strategy: start searching for a new start codon (ATG) only after the position you encountered the last stop codon (start codons between a start and a stop are ignored).

Is my call_orfs.py working? Online tools that do similar work? • http://www.ncbi.nlm.nih.gov/orffinder/ <- a useful tool for checking ORFs Notes for this tool: 1: an ORF is allowed to run to the end of the contig (no STOP codon required) 2: it only reports the longest ORF

More tools? • See http://en.wikipedia.org/wiki/Open_reading_frame

Take home messages: • Small changes in prediction model input

-> large changes in output • Gene prediction -> identify new potential genes from unknown

• Many methods exist for annotation -> performance comparison + check for assumptions • Non-ATG start codons exist in prokaryotic genomes! They still code for a modified Met (fMet)