Which of the following are usually identical between a lung cell and a brain cell, from the same person, assuming that they are normal (non-cancerous) cells? Circle your choice(s).

a.  Size
b.  Shape
c.  Specific proteins found in the cell
d.  Specific genes in the cell’s genome
e.  Which genes are expressed
f.  Which parts of the DNA are methylated
g.  The specific DNA sequence of chromosome 12
h.  All of the above
i.  None of the above

I said only D and G because all cells have the full genome. The difference between cells is how the these genes are expressed. All of the other options are results of different amound of gene expression. Is this the correct thinking?

  • $\begingroup$ Seems right. I would choose those answers as well. $\endgroup$ Oct 3, 2012 at 16:49

1 Answer 1


I would also go for d and g. All the others may vary. Strictly speaking, you may even have random, point mutations that have changed the genomic sequence between two given cells so even d and g might not be true in some cases.

I would also like to point out that recent evidence implies that differential expression of non coding, regulatory RNA molecules may play as, or even more, important a role as differential expression of proteins. See the ENCODE papers or here for a recent review.


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