[BioC] issue of genome build versions when using biomaRt

[Al Tango]

Hi all,  Although seems a frequently asked question, I didn't find it
in archives.

When specify chromosomal coordinates for a region in using biomaRt or
other BioC packages, how can I know the version of genome assembly
being retrieved, and is it possible to define a particular version to
use?

eg, I am searching for 5'UTR sequence of gene(s) within a region this way:

ensembl = useMart("ensembl", dataset = "hsapiens_gene_ensembl")
getSequence(chromosome=3, start=185514033, end=185535839,
type="entrezgene", seqType="5utr", mart=ensembl)

My questions: does it treat the start/end coordinates as in the latest
version of builld 36 (2006)? can I opt for build 35 or hg17 (2004)?

Thanks for your help in advance.