question_answer 67)

  The total number of genes in humans is far less (<25000) than the previous estimate (up to 140000 gene). Comment.

Answer:

                  The total number of genes is estimated at 25000 much lower than previous estimates of140000 that had been based on extrapolations from gene-rich areas as opposed to a composite of gene-rich and gene-poor areas.Almost all (99.9%) nucleotide bases are exactly the same in all people. Functions for over50% discovered genes are not known yet. Scientist have identified about 1.4 million locations where single-base DNA difference (SNPs or Single Nucleotide Polymorphisms)occur in humans. This information promises to revolutionize the processes of finding chromosomal locations for disease-associated sequence and tracing human history.