The claim that human DNA is 3GB is false. I assume the assumption was that 3 billion base pairs equates to 3GB.
There are a few issues with this: 1. DNA is a quaternary sequence, not a binary sequence (Adenine, Guanine, Cytosine, Thymine). 3 Billion base pairs are informationally equivalent to 6 billion bits. 2. Human haploid cells have a single set of chromosomes composed of ~3 billion base pairs. However, somatic cell’s are diploid with 2 sets of chromosomes composed of 6 billion base pairs. The bases present at each allele are not identical and allele combinations have significant phenotypic relevance. 3. A GB is 1,000,000,000 bytes, where each byte is 8 bits.
With these adjustments, one concludes each human’s genome is ~1.5GB.
Additionally, our focus can be reduced further by considering that not all DNA directly encodes information relevant to phenotypic expression, including introns, pseudogenes, transposable elements, satellite DNA, etc.. Although subject to ongoing debate, there are primarily two definitions of function: biochemical activity (which the ENCODE project determined to be ~80.4%), and DNA conserved across mammalian species under negative selection (~8.2%, although there are a range of values). These fall further when restricted to the cell types relevant to the structure of the human brain.
The range of genome size across species is much smaller in magnitude than the differences in the number of genes, and these variables don’t appear to positively correlate. Considering many complex traits such as intelligence are highly heritable, one might expect the number of genes would be relevant but it appears not (C-Value Paradox). The solution seems to be that DNA encodes a developmental pathway, which even single nucleotide differences can permanently damage, and cell types which form complex phenotypes through emergent structures, even with their foundations in simple cellular architecture. Although, I will be careful to note that this is essentially a question which would require a full description of human development as an answer, which is clearly more complex than a few sentences.
The claim that human DNA is 3GB is false. I assume the assumption was that 3 billion base pairs equates to 3GB.
There are a few issues with this:
1. DNA is a quaternary sequence, not a binary sequence (Adenine, Guanine, Cytosine, Thymine). 3 Billion base pairs are informationally equivalent to 6 billion bits.
2. Human haploid cells have a single set of chromosomes composed of ~3 billion base pairs. However, somatic cell’s are diploid with 2 sets of chromosomes composed of 6 billion base pairs. The bases present at each allele are not identical and allele combinations have significant phenotypic relevance.
3. A GB is 1,000,000,000 bytes, where each byte is 8 bits.
With these adjustments, one concludes each human’s genome is ~1.5GB.
Additionally, our focus can be reduced further by considering that not all DNA directly encodes information relevant to phenotypic expression, including introns, pseudogenes, transposable elements, satellite DNA, etc.. Although subject to ongoing debate, there are primarily two definitions of function: biochemical activity (which the ENCODE project determined to be ~80.4%), and DNA conserved across mammalian species under negative selection (~8.2%, although there are a range of values). These fall further when restricted to the cell types relevant to the structure of the human brain.
The range of genome size across species is much smaller in magnitude than the differences in the number of genes, and these variables don’t appear to positively correlate. Considering many complex traits such as intelligence are highly heritable, one might expect the number of genes would be relevant but it appears not (C-Value Paradox). The solution seems to be that DNA encodes a developmental pathway, which even single nucleotide differences can permanently damage, and cell types which form complex phenotypes through emergent structures, even with their foundations in simple cellular architecture. Although, I will be careful to note that this is essentially a question which would require a full description of human development as an answer, which is clearly more complex than a few sentences.