cDNA sequence differences

Nikolai Chitaev nikolaic at VISAR.WUSTL.EDU
Sun Jun 16 13:29:27 EST 1996


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Leo writes:
> My question may be a simple one but it is important
> to my research and I will be grateful if someone can
> provide me some information.
> 
> Recently we have isolated a cDNA clone from a Stratagene
> human liver cDNA library. The deduced amino acid sequence of
> the gene product matched very well with that of the enzyme
> we are interested in. Only two substitutions out of 400 or so
> amino acid residues were noted. The nucleotide sequence of
> the cDNA also matched several human EST files in GenBank.
> However, the homology between the cDNA sequence and those of the
> human EST files is only 93%.
> My questions are:
> 1. Is it possible that the Stratagene cDNA library is not human origin?
			I don`t belive it is possible.

> 2. Did anyone has a similar experience ?
			I did. I isolated dene of interest from cDNA and after sequencing found it has two
 nucletide missmatches. It the former case it was "silent mutation" in the later case
it leads to substitution of Arg to Cys. In both cases it was C to T substitution. I run my
sequence agains GenBank and found two matching sequences, however, while the gene`s name
was the same the % of similarity varied from 99% to 87%.

> 3. How reliable are the commercial cDNA libraries (in terms of
> their source) ? For an example, I have heard a laboratory has
> isolated a bacterial gene from a human cDNA library.
			I would belive, that that laboratiry contaminated their source of cDNA at a first place.

> 4. How different should I expect to see when comparing cDNA sequences
> of a housekeeping enzyme derived from two different individuals
> (of two different races) ?
	At least you should not be suprised, when found the differense.

-- 
Nikolai
http://128.252.119.253

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<h1>cDNA sequence differences</h1>
<b>Leo</b> (<a href="mailto:klebs.bbs at bbs.life.nthu.edu.tw"><i>klebs.bbs at bbs.life.nthu.edu.tw</i></a>)<br>
<i>16 Jun 1996 07:29:14 GMT</i>
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<pre>
To: <a href="mailto:methods at net.bio.net">methods at net.bio.net</a><br>
From: <a href="mailto:klebs.bbs at bbs.life.nthu.edu.tw">klebs.bbs at bbs.life.nthu.edu.tw</a> (Leo)<br>
Subject: cDNA sequence differences<br>
Date: 16 Jun 1996 07:29:14 GMT<br>
</pre>
<p>
<p>
<p>
  My question may be a simple one but it is important<br>
 to my research and I will be grateful if someone can<br>
 provide me some information.<br>
<p>
  Recently we have isolated a cDNA clone from a Stratagene<br>
  human liver cDNA library. The deduced amino acid sequence of<br>
  the gene product matched very well with that of the enzyme<br>
  we are interested in. Only two substitutions out of 400 or so<br>
  amino acid residues were noted.  The nucleotide sequence of<br>
  the cDNA also matched several human EST files in GenBank.<br>
  However, the homology between the cDNA sequence and those of the<br>
  human EST files is only 93%.<br>
 My questions are:<br>
  1. Is it possible that the Stratagene cDNA library is not human origin ?<br>
  2. Did anyone has a similar experience ?<br>
  3. How reliable are the commercial cDNA libraries (in terms of<br>
     their source) ? For an example, I have heard a laboratory has<br>
     isolated a bacterial gene from a human cDNA library.<br>
  4. How different should I expect to see when comparing cDNA sequences<br>
     of a housekeeping enzyme derived from two different individuals<br>
     (of two different races) ?<br>
<p>
  Thank a lot for your kind response.<br>
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