Research on the genes responsible for color discrimination

It has long been noticed that the impairment of the ability to distinguish between red and green colors is more common in men than in women. The analysis of such data indicated that the anomaly is caused by genes that are part of the X chromosome (sex-determining). In men, the inability to distinguish between red and green colors is manifested when there is a defective gene in their single X chromosome, which is inherited from their mother. In women, this anomaly appears only if they have received a defective X chromosome from both parents. Studies have also shown that variations in sensitivity to blue color depend on some kind of gene outside the sex-determining chromosome. We decided to test the assumption that hereditary color vision disorders are caused by changes in the genes encoding cone pigments. Mutations in such genes should lead to the loss of functional pigment or to the synthesis of pigment with an abnormal absorption spectrum.

We isolated the genes encoding color pigments and compared their structure in people with normal and abnormal color vision. To isolate a gene, the amino acid sequence of the protein encoded by it is often determined, and the structure of the gene is determined by it. But since, when we started our work, practically nothing was known about the structure of the proteins of color pigments, we had to choose a different approach.

We assumed that the cone pigments and rod pigment rhodopsin originated from a common visual precursor pigment, and therefore modern genes probably have some similar DNA sequences. If the structure of the rhodopsin gene were known, we reasoned, it would be possible to learn something about the structure of cone pigment genes. By that time, neither human rhodopsin nor its gene had yet been isolated, but it was possible to obtain bovine rhodopsin from the retina of cattle. Moreover, Y. A. Ovchinnikov and colleagues from the Institute of Bioorganic Chemistry named after Shemyakina in Moscow and R. Hargreave and colleagues from the University of Southern Illinois have deciphered its amino acid sequence. This information formed the basis of our work on the identification of genes encoding cone pigments.

We intended to isolate the bovine rhodopsin gene and then use the DNA hybridization method, using the resulting gene as a probe, to identify the human genes of rhodopsin and cone pigments. This method is based on the ability of a single strand of DNA to form a stable double helix with a second strand if their nucleotide sequences are complementary (adenine is parenteral to thymine, and guanine to cytosine). The double-stranded DNA under study is cut into fragments and each fragment is cloned to obtain multiple copies of it. A DNA sample from each clone is divided into single strands and a radioactive probe is added — another fragment of single-stranded DNA complementary to the identified gene. The probe must stably contact the complementary site, thus revealing the desired gene. New players can get a welcome bonus of up to €1500 + 150 Free Spins at Enter our 1xbet promo code in the registration form to get a 100% first time deposit welcome bonus. 18+. Minimum deposit: €10 (or equivalent currency). All deposit bonuses must be redeemed by wagering the bonus amount х35 times within 7 days. Until the bonus has been redeemed, stakes cannot be higher than €5 (or equivalent currency).

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