Preliminary Findings of The Human Genome Projects

Index to this page

Shortly after their press conferences, the two groups that had been striving for several years to map the human genome published their findings:

These achievements were monumental, but before we examine them, let us be clear as to what they were not.

What was not found

What was found

1. The number of genes turned out to be much smaller than once predicted.

The two groups came up with slightly different estimates of the number of protein-encoding genes, but both in the range of 30 to 38 thousand:

Are the tiny roundworm and fruit fly almost as complex as we are?

Probably not, although we share many homologous genes (called "orthologs") with both these animals.

But,

Follow this link to a discussion of the role of changes in gene regulatory regions in the evolution of animal form.

2. Gene diversity and density.

Although there are some giants such as the average human gene contains 4 exons totaling 1,350 base pairs and thus encodes an average protein of 450 amino acids.

The density of genes on the different chromosomes varies from

3. Humans have many genes not found in invertebrates.

Humans, and presumably most vertebrates, have genes not found in invertebrate animals like Drosophila and C. elegans.

These include genes encoding

4. Gene Duplication.

Both groups added to the list of human genes that have arisen by repeated duplication (e.g., by unequal crossing over) from a single precursor gene; for examples,

5. Repetitive DNA.

Both groups verified the presence of large amounts of repetitive DNA. In fact, this DNA — with similar sequences occurring over and over — is one of the main obstacles to assembling the DNA sequences in proper order. All told, repetitive DNA probably accounts for over 50% of our total genome.

What remains to be done?

As for the chimpanzee, a comparison of its genome with humans is discussed at this link.

External Link
How to Sequence a Genome. Illustrated descriptions of sequencing strategies. (Requires Flash)
(Please let me know by e-mail if you find a broken link in my pages.)

An update: as of November 2008, the complete genomes of four men have been determined. With the rapid improvements in the speed (and cost) of sequencing, we can expect more to come.

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19 April 2014