The way Kyte-Doolittle plots work, if the graph shows a peak that reaches about 2 or higher, then there is the potential for a transmembrane domain.
1) Go to this page <bio.davidson.edu/courses/genomics/chime/leptinseq.html> and copy and paste the sequences for leptin or its receptor. You can compare the predictions with reality.
Leptin is secreted and has no transmembrane domains while its receptor has one transmembrane domain. Because leptin is secreted, it does contain a signal sequence at its very beginning and this sometimes produces a peak near 2 by this method. Does it for leptin?
2) Go to this web page <http://occawlonline.pearsoned.com/bookbind/pubbooks/bc_mcampbell_genomics_1/medialib/activities/kd/kyte-doolittle.htm> to generate a Kyte-Doolittle plot.
3) Paste in your sequence and hit "Plot" You will get a graphic output of the Kyte-Doolittle hydropathy plot to predict if your sequence can span a membrane or not. Did the prediction match what is known about leptin and its receptor?
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