Which of the following accounts for allelic exclusion in rearrangement within the IgH locus?
A. Rearrangement only occurs on one homolog at a time, and once one homolog has successfully rearranged, the other is methylated to produce heterochromatin.
B. Rearrangement is regulated by VpreB and ?5, which are themselves only expressed at specific times during IgH rearrangement.
C. Both homologs rearrange simultaneously, undergoing multiple V-J rearrangements until a productive one occurs.
D. All of the above promote allelic exclusion in IgH.
E. Allelic exclusion does not occur in IgH.
Answer: A
Biology
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- Achaeans can tolerate which of the following extreme habitats?
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- ____ were the dominant vertebrate life form during the Mesozoic era.
- Most modern animal phyla evolved during the _____ era.
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