What exactly is a gene?

[skyisblue]

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Is a gene a sequence of 3 nucleotides or is it a sequence of 3 nucleotide pairs?

 

[blasterx]

A segment of DNA that encodes for a protein.

 

[poc91nc]

Depends on who you talk to...but the way I learned it was..a gene includes EVERYTHING...all regulatory regions (ie cis element)...exonic sequence, intronic sequence...the whole nine yards

 

[jdmsamurai]

Depends on who you talk to...but the way I learned it was..a gene includes EVERYTHING...all regulatory regions (ie cis element)...exonic sequence, intronic sequence...the whole nine yards

not everything...enhancers, promotors, TATTA box, and the deeply repeated sequences of ATATATAATA fingerprint repeats... etc...they dont code for anything or so i think....they can be extra binding sites etc...so i dont think they count as a gene...i like the idea of a "gene gets encoded into a protein that has a phenotypical effect on the host"

 

[poc91nc]

Right...like I said, depends on who you talk to. Nonetheless they are still functional units of gene expression. As far as intronic sequences are concerned...hard to say why that would be part of one person's definition. But...I just looked at my old biochem notes...and this was the working definition from day one of the molecular genetics unit. For the record I have heard different definitions as well.

My background is in biochemistry...so maybe we come from different perspectives.

Here is a definition from Alberts Molecular Biology of the Cell:

Gene: "Region of DNA that controls a descrete hereditary characteristic, usually corresponding to a single protein or RNA. This definition includes the entire functional unit, encompassing coding DNA sequences, noncoding regulatory DNA and introns."

I was told by a lot of people that this is a pretty heated debate as far as what a gene is....so..yeah.

 

[jdmsamurai]

youre right....also that definition is only good for eukaryotes....due to splicing and mutation i think introns can become exons and exons can become intros...(bits and pieces)....but very hot debate....

and remember a textbook is just an authors point of view....until i see a universal national standard for something like in programming languages...then its just a point of view...kudos to all

 

[jdmsamurai]

i was thinking what about the noncoding NON-regulatory sequences??? does that count as genes since it wasnt in your definition...haha 😉

 

[dewdrinker23]

Right...like I said, depends on who you talk to. Nonetheless they are still functional units of gene expression. As far as intronic sequences are concerned...hard to say why that would be part of one person's definition. But...I just looked at my old biochem notes...and this was the working definition from day one of the molecular genetics unit. For the record I have heard different definitions as well.

My background is in biochemistry...so maybe we come from different perspectives.

Here is a definition from Alberts Molecular Biology of the Cell:

Gene: "Region of DNA that controls a descrete hereditary characteristic, usually corresponding to a single protein or RNA. This definition includes the entire functional unit, encompassing coding DNA sequences, noncoding regulatory DNA and introns."

I was told by a lot of people that this is a pretty heated debate as far as what a gene is....so..yeah.

The non-coding regions are called junk DNA. Junk DNA is a term that was coined to describe a region(s) on a chromsome that does not code for a protein. Thus, these junk DNA do not contain genes. However, these regions have been shown to have a regulatory impact on the genes that do code for proteins.

A gene is not a simple sequence of letters. There is no definition that holds up to a scientific argument that supports a gene being a certain amount of nucleotides. Thus, the area of a sequence that results in coding is what we call a gene. This can include RNA, RNAi, tRNA, etc.

 

[poc91nc]

So...are you saying you disagree with the definition? Doesn't intronic sequence quality as a non-coding region?

 

[lotexigeus]

Is a gene a sequence of 3 nucleotides or is it a sequence of 3 nucleotide pairs?

i think you're thinking of a codon. Which is a group of three nucleotides in mRNA that code for a specific amino acid in translation.