08 September 2009

Questions/Clarification From This Week's Readings

So I was a little unclear about a couple of the learning objectives from this week's reading

Unit 5 Question 7 sks us to "Calculate the minimal number of genes required to code for a million different antibody molecules based on the outdated concept of 'ong gene one H or L chain.'"

In the text, to make a hundred trillion antibodies it takes 10^14 genes. So I'm going to go ahead and assume that this is the correct formula to follow to calculate the number of genes required to make a million antibodies. So could the answer be 2*10^3?

Unit 6 Question 12 on the asks us to "discuss how complement is important in immunity to bacteria even if the bacteria are resistant to lysis by C9."

To my understanding, both C9 AND C8 form lesions on the target cell membrane, which causes the target cell to lyse. Is the answer to this question just that it's not that big of a deal if the bacteria is resistant to lysis by C9 because C8 can also cause the target bacteria to lyse? (I am a little suspicious because that seems a bit too obvious/simple...)

Thanks for the help whoever responds to this post!!!
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2 comments:

  1. JJ CohenSeptember 9, 2009 at 5:34 PM

    I think you are right; if it takes one gene to make one L chain, and one to make one H chain, it would take 2000 genes (1000H, 1000L) to make a million Abs. But as we saw in class, it's even cleverer, because we use minigene segments and N-region randomization.

    I was thinking that if you don't have C9 you don't get lysis; C8 doesn't make holes, it helps C9 assemble into holes. But without C9, you would still have chemotaxis, opsonization and anaphylatoxins to release histamine, and those 3 mechanisms could get rid of a lot of bugs!

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  2. AmyR7630September 12, 2009 at 2:54 PM

    I concur with the above post. :) Also, here is a video which may help visualize the classical complement pathway from the initial activation of complement to the death of a bacteria. Bacterial lysis is due to the formation of a pore made up of C9 molecules. The C5b678 complex catalyzes the assembly of C9 molecules.

    http://www.youtube.com/watch?v=vbWYz9XDtLw

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