Human Chromosome 22 Mapped

tuck was the first of many to submit this important milestone in arguably the world's most important scientific endeavor. The Human Genome Project has completed mapping its first entire chromosome, number 22. Second-smallest of our 23 chromosomes, some of 22's genes can cause "heart defects, immune system disorders, cancers, schizophrenia and mental retardation." Portion of its DNA which is "junk" (encodes no protein): 42%. Read it at your favorite source: CNN, MSNBC, the Boston Globe, the Christian Science Monitor, the AP, or Reuters.

Comments

The HGP is like the Periodic Table

[wowbagger]

The analogy I like to use for the Human Genome Project is the development of the Periodic Table of elements.

Of itself, the periodic table didn't make any new chemicals. What it did was provide a framework to identify patterns that could be used to predict areas of research. For example, the discovery of helium: the table predicted the existance of the element, and allowed calculation of the spectral lines. The element was then identified in the sun, hence the name (helium, from helios, the sun).

Similiarly, the HGP of itself won't cure any diseases; rather it will allow the mapping of patterns. We'll be able to say, "This gene, which we know does this in wheat, is present in humans. Perhaps it does the same thing?".

Once we get one copy of the human genome sequenced, we'll still need to sequence many others, from [tall|short|skinny|fat|bald|hairy...] people, and start cross-referencing the results.

Think of it as a massive reverse engineering project on a program we only have uncommented object code for.

Unless the "junk" DNA are comments...

I Decoded the Junk DNA...OH NO

[MagusOceanus]

I extracted the Junk DNA and respliced it so that it would stand without the DNA that is neccessary to humans, inserted it in a cell and watched it grow. 5 hours later to my horror it took a flat retangular shape, black lines appeared on a white surface. They connected to form letters in clear English which read...

"Mr _________ , You have been selected as a final entry for the Publisher's Clearinghouse largest drawing, enclosed is a Check worth $30,000,000 if you have the winning number!!! Please open and send your entry form within the next 24 hours, and get a GUARANTEED prize."

I tried the Junk DNA of other chromosomes and got ads for term life insurance, timeshares, and then the Junk DNA materialized in front of me into a pushy Amway distributer!!!! The horror!!! Cellular SPAM!!! AGHHHHHHHH

What does that mean?

[jw3]

In a recent /. discussion we argued about the Human Genome Project v. TIGR. As you see, the HUGEP is doing quite well. The raw data from the sequencing project should be available next year.

Will this finish a task? No, it is just a beginning - having the sequence, the real work starts: searching ORFs (Open Reading Frames - sequences which could possibly be genes), running database searches, and slowly passing to the most exciting fields of modern molecular biology - from genomics to transcriptomics and proteomics. Transcriptomics is looking for genes, which actually got expressed, and proteomics - similarly, looking for expressed proteins. Making transcription / translation (translation is the process in which proteins get synthetized) profiles can lead us to 1) function of proteins (e.g. protein X. is expressed under this and this conditions, so it must take part in this and this metabolic response) 2) regulation - DNA is a single strand, but various enzymes are present in various copy numbers under various conditions.

Those are enormous projects. A lot of work has to be done before the raw sequence will actually be of any use; nethertheless, it is a milestone of molecular biology and will be a fine achievement for the end of our century.

Another project will be to determine the variability of human genome: screening for different gene allels, mutations etc. This will be one of the most important goals in human genomics in the next few years.

Whats on the catch... erm, chromosome 22? 22 is 33,400,000 bases long (Mycoplasma pneumoniae, one of the smallest bacteriums, has about 816,394 bases). It contains several already known genes responsible for various genetic disorders, and possibly a gene responsible for certain types of schizophrenia.

By the way, a much better source of information is the Nature science update page - the original scientific publication has been published today in Nature.

Regards,

January

To understand "junk" DNA, look at the big picture

[whuppy]

First of all, "junk" is a loaded term, which is certainly evidenced by all the nonsense it has spawned in this discussion. So let's do this by enumerating the different types of DNA a typical eukaryotic genome contains:
1. Coding Regions. DNA that gets transcribed to RNA. RNA transcripts in turn have exons, which get translated into proteins, and introns, which get spliced out before translation. Why this added level of complexity? Many reasons. In sexual reproduction, new chromosomes are produced by mixing and matching old chromosomes at random. It's more likely for the new chromosome to be functional if the crossover point is in an intron because crossovers can introduce mutations, especially a nasty sort of mutation called a frameshift which would render everything downstream unintelligible. Exons also allow for a certain modularity of function, evolutionary mutations can involve entire exons being combined instead of having to try changes on a base-by-base level.
2. Regulatory regions. DNA that turns other bits of DNA up or down. Mainly used to control transcription, but also used to control DNA replication.
3. Structural regions. Eukaryotic DNA is a huge, long, string requiring a certain amount of overhead to prevent it from becoming an unmanagable tangle. Lots of the chromosome is dedicated to binding to structural proteins, generally known as histones, around which the DNA is wound. Also centromeric and telomeric proteins.
4. Repeats, cryptic genes, etc: In order to avoid overloading the term "junk," let's call this category "cruft." Cruft arises for lots of reasons. For example, sexual reproduction produces gametes, and it's far from perfect: Regions get repeated, regions get dropped. So called cryptic genes are probably the result of a spliced RNA being reverse-transcribed back into DNA and reinserted into the genome without introns or regulatory elements. What's useful about the cruft is that it provides fodder for further evolution.
In summary: Eukaryotes are big and complex, which means that you have to allow for a certain amount of overhead and slop.
I hope this has helped.