Telomeres and Spock



"my what lovely telomeres you have" said the wolf-virus
to the little red-riding hood-cell

 


  Cells have their own version of Spock's famous missive "Live long and prosper."  Cells make this statement using repetitive DNA sequences found on end of chromosomes called "telomeres." Telomeres act as a cap on the end of chromosomes.  They are thought to be another "guardian of the genome" of sorts.  Some scientists believe that longevity is related to telomere length. In fact, telomeres have been shown to be longer in individuals who are healthy and exercising compared to individuals who are under stress.



What's even more interesting is that telomeres are thrown out or lost during cell division so they have to be "remade" using a specific polymerase.



How do telomeres protect DNA?

What is the significance of telomeres being made from repetitive DNA? (what is repetitive DNA and what is it good for?).

What determines how long telomeres are?

How are telomeres related to cell function?

Some bacteria have telomeres,  so from one perspective it looks like they were handed down via evolution.  Why use what appear to be accidental sequences to make the ends of chromosomes? Is there some advantage or design feature inherent in these chromosomal pieces?

inTRON Legacy... the problem of snRNPs (the smurfs of cell biology)

A recent study highlights the importance of spliceosome components by showing that a rare genetic disease is caused by a mutation in a

snRNP.  The spliceosome is a machine made of several snRNPs.  These molecular scissors cut precisely the right location on the DNA to remove an intron and promote the ligation of exons.  Prokaryotes appear to do just fine without introns. 

 So what is the purpose of introns?  What overall function do they provide for eukaryotes?  Why use such a complex splicing operation for a function which appears to do nothing more than rejoin exon regions?   How do evolutionary biologists propose that snRNPs and spliceosomes evolved? Is this good design or is this entire process wasteful and therefore not good evidence for design in nature?

location location location, position of chromosomes, gene expression, and bad design?

garage DNA ..what a mess?

The amazing organization of the eukaryotic nucleus was shown in a fascinating article in Scientific American.  It turns out that chromosomes occupy certain locations in the nucleus.  Some chromosomes reside at the periphery of the nucleus and others near the middle.  Some chromosomes also appear to favor being next to "buddy" chromosomes.  It is not yet totally understood why chromosome position is important, except that it is very crucial to cell function.  One nucleoskeletal protein lamin, helps tether the chromosomes in place.  Mutations in lamin are responsible for all sorts of disease conditions, including progeria, or premature aging.


Also it appears that the chromosomes near the nuclear periphery are more quiescent than chromosomes near the center.  The chromosomes in the center are more involved in gene expression.  No one knows how the chromosomes get directed toward a specific place in the nucleus.  I find it quite amazing that this overall structure can be maintained because there is so much DNA in the nucleus.  Remember in its stretched out form DNA is  hundreds of thousands of times longer than the nucleus diameter.   I have trouble just keeping a few power cords untangled in the garage.  Just imagine my garage packed full of tightly wound-up and partially wound-up power cords  and that I need to find one cord in particular to unwind and use and I must do this while literally swimming through a tangled maize of power cords.  I think you would suffer from "power cord" entrapment before you could even reach the power cord you need. 


1 Investigate progeria and hypothesize how nuclear organization could lead to this syndrome and other disease states.  Many diseases are related to chromosome structure and function including cancer, does this support the notion of bad design?....i.e., does the fact that some aspects of cell structure are more involved in promoting disease states show that a designer of the cell or life is unlikely ?




2 Describe how nuclear organization and chromosome location could evolve during the evolution of the nucleus from a prokaryote ancestor? What are some of hurdles that evolution would have to overcome?