The dopamine D2 receptor locus as a modifying gene in neuropsychiatric disorders

Article Abstract:

Dopamine is a chemical substance that plays an important role in the transmission of certain nerve signals. It is thought that abnormalities related to dopamine and its actions could be responsible or partially responsible for some neurological and psychiatric disorders. A few studies have reported an association between alcoholism and the presence of a variation of a gene associated with the expression of the dopamine D2 (DRD2) receptor, labelled the A1 allele. Other studies have not found such an association. These conflicting results could be explainable if the A1 allele is a modifying gene related to alcoholism as opposed to being a gene specifically responsible for alcoholism. To test this hypothesis, the prevalence of the A1 allele in various groups of people was measured. A total of 853 subjects were examined, including 314 healthy control subjects, 147 subjects with Tourette's syndrome (TS), 104 with attention deficit hyperactivity disorder (ADHD), 33 with autism, 104 who were alcoholics, 35 who suffered from posttraumatic stress syndrome, 13 who suffered panic attacks, 17 who had Parkinson's disease, and 10 who were obese. The A1 allele was found in 24.5 percent of the control subjects. It was found in 44.9 percent of subjects with TS, 46.2 percent of subjects with ADHD, 54.4 percent of the autistic patients, and 42.3 percent of the chronic alcoholics The prevalence for all of these groups was significantly greater than that in the control group. The differences in prevalence between the control group and the other groups studied were not statistically different. These results indicate that the A1 allele is related to, but not the direct cause of, a number of neuropsychiatric disorders. (Consumer Summary produced by Reliance Medical Information, Inc.)

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Prenatal determinations of paternity by molecular genetic ''fingerprinting''

Article Abstract:

Pregnancies resulting from sexual assault or the result of multiple sex partners may benefit from information obtained from molecular genetic ''fingerprinting'' to determine the actual father (paternity). Direct molecular genetic analysis of the genetic material, DNA, eliminates some of the problems experienced when fetal tissue protein analysis (karyotyping) is used to determine parentage. Two case studies requiring analysis of parentage were evaluated using DNA fingerprinting techniques. During routine genetic counseling, a 35-year-old married woman admitted to having a sexual liaison with another man. The woman wanted to continue the pregnancy only if her husband was the father. Fetal tissue obtained during amniocentesis was analyzed to determine the hybridization patterns. The patterns were compared with those of the two potential fathers. Although some of the DNA fragments matched the nonhusband, the majority did not, thereby excluding him as the father. All of the fragments present in the fetal analysis were present in the husband's genome. Additional tests confirmed the results obtained during DNA fingerprinting. In another case, a 34-year-old woman was raped during a period when she was being treated with clomiphene citrate, an ovulation-inducing agent used to treat infertility. All of the 51 fragments obtained by chorionic villus sampling, a method of early prenatal diagnosis, matched the woman and her husband. DNA fingerprinting is easily performed and produces rapid accurate results to determine paternity. (Consumer Summary produced by Reliance Medical Information, Inc.)

Methods, Case studies, Evaluation, DNA testing, DNA identification, Prenatal diagnosis, Paternity testing

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No association between an allele at the D2 dopamine receptor gene (DRD2) and alcoholism

Article Abstract:

Dopamine is a chemical substance that plays an important role in the transmission of certain nerve signals to and from the brain. Abnormalities of the D2 dopamine receptors have been suggested as a cause or a partial cause of some neurological and psychiatric disorders. Previous researchers have reported that a variation of the D2 dopamine receptor gene (DRD2) known as the A1 allele was present at a significantly higher rate in alcoholics than in nonalcoholics. Other studies have reported similar findings, while yet others have reported no association between the A1 allele and alcoholism. To further examine this issue, the allele at the DRD2 gene locus was determined in 44 alcoholics and 68 control subjects. All subjects were white and none were biologically related. The A1 allele was found in 35 percent of the control subjects and in 45 percent of the alcoholic subjects. Differences between alcoholics and controls in overall frequencies of the A1 and A2 alleles at DRD2 were not considered statistically significant. When the subjects in the alcoholic group were further subdivided into groups based on family history of alcoholism, age at onset, and consumption, the prevalence of the A1 allele was not significantly different for any of these subgroups compared with that of the control group. It is concluded that there is no association between the A1 allele of the DRD2 and alcoholism. (Consumer Summary produced by Reliance Medical Information, Inc.)

Diagnosis, Causes of, Genetic disorders

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