Question about DNA/heredity info

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aqua_eyes23
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Question about DNA/heredity info

Post by aqua_eyes23 » Fri Jan 21, 2005 2:51 am

How can you account for 95 % of the human DNA carrying no apparent functional heredity information? There are about 25,000 genes which dictate proteins structure in the remaining 5%. How can you account for the fact there are roughly 100,000 genetically specified proteins but only 25,000 genes?

Thanks so much for the help

Sara

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biostudent84
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Post by biostudent84 » Fri Jan 21, 2005 6:28 am

I think you heard a very liberal estimate. It's more like 10% of the DNA we have is used. The rest is termed "junk DNA." The majority of the hypotheses include DNA left over from evolution, and useless genetic material placed into the sequence by viruses. Don't forget that DNA when stretched out is almost 24 miles long. 2.4 miles of DNA can still carry a heck of a lot of information.

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Post by RobJim » Thu Feb 10, 2005 1:09 am

Aqua_eyes23 -

How can you account for 95 % of the human DNA carrying no apparent functional heredity information?

I'm not sure how you want me to "account" for this. Why does this bother you? What needs explaining?

How can you account for the fact there are roughly 100,000 genetically specified proteins but only 25,000 genes?

Some genes make polypeptides which are then cut into multiple proteins by enzymes. This results in several small proteins coming from one long gene.

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canalon
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Post by canalon » Sun Feb 13, 2005 5:52 pm

The rest is termed "junk DNA." The majority of the hypotheses include DNA left over from evolution, and useless genetic material placed into the sequence by viruses. Don't forget that DNA when stretched out is almost 24 miles long. 2.4 miles of DNA can still carry a heck of a lot of information.


Be carefull! The so called "junk DNA" may not be just leftovers and useless as it has been thought. It's just we don't know what it's used for.
Some explanation are suggested, as just being used as spacer between genes, that could be important to explain different transcription level (moving a gene out of a coiled DNA region, or farther from a strong promoter...).
So all this DNA DNA is probably not just junk. Otherwise evolution would have strongly selected against such a heavy load of junks in our genomes.

Patrick

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meenkashi
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Post by meenkashi » Tue Sep 02, 2008 3:13 pm

junk dna is nthng but strands formed by d non-sense codons........
its knwn dat same amino acids and odr substances r producd by evryone in an equal qty. but still der r differncs..........dats coz o da prescence of junk dna.......in short.....it differentiates person to person by d amt of it presnt in dem.....

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jonmoulton
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Re: Question about DNA/heredity info

Post by jonmoulton » Thu Sep 04, 2008 3:11 pm

How can you account for 95 % of the human DNA carrying no apparent functional heredity information? There are about 25,000 genes which dictate proteins structure in the remaining 5%.


There are RNAs transcribed from some of the regions that do not code for protein structure. Some of these have regulatory roles, for instance, natural antisense transcripts or, for another example, miRNAs. The intergene regions are also the scratchpad for evolution, where inactivated genes can be recombined and mutated then reactivated.

How can you account for the fact there are roughly 100,000 genetically specified proteins but only 25,000 genes?


I'm surprised no one mentioned alternative splicing of pre-mRNA. This is a very common method for eukaryotic cells to generate groups of distinct proteins from single genes.

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