Has this already been discussed somewhere on the site?

X-Man

Genetics has been discussed in various placed through out the forum but weather or not this specific area has been addressed, I was unable to find it upon search, but this search engine doesn't like me much any way.

Are you thinking along the lines of genetic evolution and ADD or a broader category?

There has been general discussion regarding the evidence that ADHD is a hereditary, genetic trait, looking at fMRI, PET, and SPECT scans, family histories, twin studies, and gene studies. There's been mention of a few studies that have shown (and possibly confirmed) that certain differences in DRD4 appear to have a strong correlation with ADHD.

However, I haven't seen much discussion of the specific region in the gene, or the specific variations that occur. If you have any information on DRD4, assuming that it's from a reputale source, it would definitely e worth posting it.

Here is some of the information on scientific sites.

Abstract TOP (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#top)


Several previous studies found an association of clinically diagnosed attention deficit hyperactivity disorder with long alleles of a variation in the DRD4 dopamine receptor gene exon III coding sequence. We evaluated the DRD4 polymorphism in a non-clinically selected sample of children for whom maternal reports of attention problems were available at 4 and 7 years of age. There was a significant elevation in attention problem scores in children carrying DRD4 long alleles that accounted for 3-4% of total variation at each age and for 5-7% of the temporally stable component of the phenotype. Our results show that the DRD4 gene influences normal as well as pathological attention processes, and the results highlight the utility of longitudinal measurements in psychiatric genetics.

INTRODUCTION TOP (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#top)


The D4 dopamine receptors (DRD4s) belong to the D2-group of dopamine receptors and are predominantly expressed in a restricted set of dopamine-rich limbic areas that are involved in cognition and emotion. Both pharmacological and genetic experiments suggest that D4DRs play important roles in attentional, motivational, and exploratory neurobehavioral processes. The human DRD4 gene, which is located on chromosome 11p15.5, contains a highly polymorphic 48 base pair variable number of tandem repeats sequence in exon III. This polymorphism, for which the four- and seven-repeat alleles are most common, lies in the third cytoplasmic loop of the receptor and has been reported to have modest effects on both ligand binding and receptor-mediated modulation of intracellular cyclic AMP levels (Vantol et al., 1992 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P77);Asghari et al., 1994, 1995 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P41)).

There have been numerous studies on the possible role of the DRD4 exon III polymorphism in human behavior, personality, and psychiatric disorders. The most consistent results involve attention deficit hyperactivity disorder (ADHD), a common neuropsychiatric disorder with childhood onset that is characterized by problems with attention, information processing, overactivity and impulsivity. ADHD is known to have a substantial genetic component from family, twin and adoption studies, and dopaminergic genes are reasonable candidates for this effect in view of the fact that the most common pharmacological treatment of the disorder is with drugs such as methylphenidate that alter dopamine transmission (Faraone and Biederman, 1998 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P54);Thapar et al., 1999 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P75)). There have now been eight reports of an association between ADHD and DRD4 allele 7, which is the most common long variant of the exon III polymorphism (LaHoste et al., 1996 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P62);Rowe et al., 1998 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P70);Smalley et al., 1998 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P71);Swanson et al., 1998 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P73);Comings et al., 1999 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P48);Faraone et al., 1999 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P55);Muglia et al., 2000 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P66);Tahir et al., 2000 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P74)). These positive findings have included both population-based case-control studies and within-family designs, and they have employed several different types of diagnostic criteria. One study found that the association was strongest for inattentive-type ADHD (Rowe et al., 1998 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P70)). However, there have also been four reported failures to find association between DRD4 and ADHD (Castellanos et al., 1998 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P47);Eisenberg et al., 2000 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P53);Hawi et al., 2000 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P59);Kotler et al., 2000 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P61)).

The DRD4 exon III polymorphism has also been associated with the normal personality trait of novelty seeking, with long alleles leading to higher scores (Benjamin et al., 1996 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P45);Ebstein et al., 1996, 1997 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P50);Ono et al., 1997 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P68);Noble et al., 1998 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P67);Strobel et al., 1999 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P72);Tomitaka et al., 1999 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P76)). These positive studies have used both population-based and within-family designs, various diagnostic instruments, and several different ethnic populations. Furthermore, DRD4 knockout mice exhibit a specific deficit in exploration of novel stimuli (Dulawa et al., 1999 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P49)), and novelty seeking is analogous to ADHD in that both involve a preference for new stimuli, high activity level, and impulsiveness. However, numerous other studies have failed to find an association between DRD4 and novelty seeking or other dimensions of normal personality (reviewed in Paterson et al., 1999 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P69)). Other studies have examined the relationship of the DRD4 gene to opioid abuse, other forms of substance abuse, and pathological gambling in adults (Kotler et al., 1997 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P60);Li et al., 1997 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P63);Mel et al., 1998 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P65);Comings et al., 1999 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P48);Franke et al., 2000 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P58)), and to various aspects of temperament and behavior assayed by the Brazelton and neonatal behavioral assessment scales in 2-week-old and 2-month-old infants (Ebstein et al., 1998 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P52);Auerbach et al., 1999 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P43)).

The present work examines the DRD4 exon III polymorphism in a group of children that are being followed as part of a longitudinal study of normal childhood development with an emphasis on temperament and social behavior (Fox et al., 1995, 2001 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P56);Calkins et al., 1996 (http://www.psychgenetics.com/pt/re/psychgen/fulltext.00041444-200103000-00005.htm;jsessionid=GQnfy21mS0PV2w2VT3svM0XlssbcF bJr3qyQhPtz1STFc1t9hLMn!-1725731959!-949856144!8091!-1#P46)). Based on the studies already described, we predicted that children with long alleles of the DRD4 gene would have more attention problems than children with short alleles. To test this hypothesis, maternal reports of attention problems were obtained when the children were 4 and 7 years old, and buccal cells were collected for DNA preparation. The availability of phenotype data at two different ages allowed us to examine the contribution of the DRD4 gene to the longitudinal continuity of attention problems as well as at two specific points in development.

X-Man

Reminds me I stumbled across this recently, but I haven't looked at it in detail. And I still haven't gotten around to taking a look at Dawkins' Extended Phenotype *hides under chair*

<table cellpadding="0" cellspacing="5" width="100%"><tbody><tr><td nowrap="nowrap" valign="top">
</td> <td width="100%">Barkley RA, Smith KM, Fischer M, Navia B (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=16741944&query_hl=1&itool=pubmed_DocSum)</td></tr></tbody></table>An examination of the behavioral and neuropsychological correlates of three ADHD candidate gene polymorphisms (DRD4 7+, DBH TaqI A2, and DAT1 40 bp VNTR) in hyperactive and normal children followed to adulthood.
Am J Med Genet B Neuropsychiatr Genet. 2006 Jul 5;141(5):487-98.