Are we descendents of Neandertal women?
Neandertals had coexisted with modern Homo sapiens in Europe for
some thousands of years. Some palentologists claim that Neandertals
are among the direct ancestors of modern Europeans, (despite Neandertals
had much larger brains than Europeans...). Others suggest, that
modern Homo sapiens had not interbred with Neandertals.
As mitochondrial DNA was successfuly isolated from Neandertal specimen,
it is now possible to make some genetic comparison between Neandertals
and H. sapiens. We would use this problem to practice searching
for literature and DNA sequences, using ENTREZ. First we look for
some publications in the subject.
Go to NCBI by clicking here,
and remember to set SEARCH window to PubMed.
Type or paste in "Neandertal". You should get quite a
number of hits. Actually, too many. There are several options to
narrow down your search to works dealing with DNA.
Cange the SEARCH window to "Nucleotides". Now, Neandertal
will retreive sequence items only. However, I do not recommend you
jumping into sequences right away. It is always a good idea to have
a look at methods and result sections of the published paper first.
Set the SEARCH window to PubMed. Narrow your search by simply adding
"DNA" to "Neandertal". ("Neandertal, DNA"
- or you can type Neandertal AND DNA" AND should be typed in
capitals). Now you get some abstracts (actually 7 when I am writing
this). It is easy to find out, which articles contain information
on DNA sequences: in such case there is link to Nucleotides on the
right.
Please, appreciate, that there are more and more full papers available
on the Internet through PubMed. For example, the article by Krings
et al published in PNAS can be retreived freely. Get the abstracts
of the most relevant articles by clicking at the name of the authors.
Read some of the abstracts. What is the latest (not necessarily
correct) view on interbreeding of H. sapiens and Neandertals? Was
that possible? Was that probable?
Get sequences! There are several ways to do that. Please, do them
all, to familiarise yourself with the data base.
- Some abstracts have links to "Nucleotides". For
example, the paper by Krings et. al. has links to nucleotides.
Click at the link. Read the header, identify what all the information
there is all about.
- As I am not sure where you are now at NCBI, open the NCBI
homepage again. Search with "Neandertal AND DNA"
again in PubMed. Now, set the DISPLAY window to "Nucleotide
links", and hit DISPLAY. You should get the Summary (Accession
Number and short description) for all DNA sequences related
to Neandertals. Conveniently, the full description of scuh items
can be retreived by setting the DISPLAY window to "GenBank",
or, the sequences themselves, by setting the DISPLAY window
to "Fasta format".
Get and copy one Neandertal sequence, and paste it to a text editor.
We will use this sequence later for a BLAST search.
Go to:
chapter on BLAST
