What exactly do genes do

At the start of the 20th century Archibald Garrod had proposed that inherited disorders such as alkaptonuria may be due to a defect in certain key metabolic enzymes, thus offering for the first time an explanation of how genetic information is expressed. His ideas were not really developed however, until the work of George Beadle and Edward Tatum in the 1940s, whose experiments with the bread mould Neurospora led to the formulation of the one gene, one enzyme hypothesis. Although now acknowledged to be

Replication fork

Replication fork

Figure 11.4 DNA replication in eucaryotes. Many replication bubbles develop simultaneously; they extend towards each other and eventually merge. The arrows denote the direction of the replication forks

Figure 11.4 DNA replication in eucaryotes. Many replication bubbles develop simultaneously; they extend towards each other and eventually merge. The arrows denote the direction of the replication forks

Box 11.3 One gene, one enzyme: not quite true

Beadle and Tatum proposed that each gene was responsible for the production of a specific enzyme. However all proteins, not just enzymes, are encoded by DNA, and furthermore, some have a quaternary structure (see Chapter 2) with different polypeptide subunits being encoded by different genes. The hypothesis was therefore modified to one gene, one polypeptide. Later still, it emerged that even this is not always the case, as some genes do not encode proteins at all, but forms of RNA.

somewhat over-generalised (see Box 11.3), this model proved useful in the years when the molecular basis of gene action was being elucidated.

Having established that genes are made of DNA, and having a model for the structure of DNA that explained how it was able to copy itself, the way was open in the 1950s for scientists to work out the mechanism by which the information encoded in a DNA sequence was converted into a specific protein.

Was this article helpful?

0 0
Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

Get My Free Ebook


Post a comment