Objective: To investigate association of the 48 bp variable number of tandem repeat (VNTR) polymorphism in the D 4 receptor gene ( DRD4 ) exon 3 and 40 bp VNTR polymorphism in the dopamine transporter gene ( DAT1 ) 3′ untranslated region with attention deficit hyperactivity disorder (ADHD) in Han Chinese children. Methods: The study samples were comprised of 340 ADHD children, 226 unrelated controls and 202 integrated ADHD trios (included proband and biological parents). The polymorphisms consisted of 48 bp VNTR in exon 3 of DRD4 , and 40 bp VNTR in the 3′ untranslated region of DAT1 . Associations of polymorphisms with ADHD and its subtypes were examined by: (i) comparing cases and controls; and (ii) using family based association study in an extension of exact transmission disequilibrium test (ETDT) and haplotype based haplotype relative risk (HHRR). Results: The repeat numbers at the DRD4 48 bp locus ranged from 2—6 repeats in the Han Chinese controls, with the most common being the 4 repeat (77%) and 2 repeat (19.4%) alleles. Neither the 7 repeat allele nor longer repeats were found. For the DAT1 , the repeat numbers at the 40 bp locus ranged from 6—7 repeats and 9—11 repeats. The 10 repeat allele was the most frequent (90.7%). The long repeat alleles of DRD4 (ranging from 4—6 repeats) and DAT1 (ranging from 11—12 repeats), were present more frequently in ADHD probands than in controls. Our primary analyses failed to replicate the associations between ADHD and 7 repeat allele of DRD4 and the 10 repeat allele of DAT1 . Conclusion: The long repeat alleles of DRD4 (after a stratification by gender) and DAT1 may increase the risk for ADHD in Han Chinese children.

G. The current results indicate that ADHD with DBD has more heritable backgrounds when compared with ADHD without DBD.

T were genotyped by restriction fragment length polymorphism analysis.Transmit/disequilibrium test and haplotype analysis were used to test the association of the three polymorphisms with ADHD comorbid or not comorbid DBD separately.Results:Haplotype T/G/T showed tendency of overtransmission(?2=3.470,P=0.062) to probands of ADHD with DBD, while haplotype C/G/T(?2=4.568,P=0.032) and C/G/C(?2=5.333,P=0.021) were undertransmitted to probands of ADHD without DBD,No biased transmissions of any allele were found in families with probands of ADHD with and without DBD.Conclusion:whether ADHD comorbid DBD or not comorbid DBD makes difference at the level of HTR4 gene polymrohisms.

Objective: To investigate the relationship between two HTR2C gene polymorphisms, that is C 759T and G 697C polymorphisms, and attention deficit hyperactivity disorder (ADHD) comorbid or not comorbid learning disorder (LD). Methods: Blood samples were taken from 189 trios with probands of ADHD comrbid LD (ADHD+LD) and 299 trios with probands of ADHD not comorbid LD (ADHD-LD). DNA was extracted and PCR was performed to amplify the fragments containing both C 759T and G 697C polymorphisms. Aci Ⅰ was used to detect different alleles of the two polymorphisms. Allele based and haplotype based TDT analysis were used to test the association of the two polymorphisms of HTR2C gene and ADHD-LD and ADHD+LD. Results: 759C(? 2= 6.961 , P =0.008), 697G(? 2=8.346, P =0.004), as well as 759C/ 697G haplotype were over transmitted(? 2=9.000, P = 0.002 7), while haplotype 759T/ 697C was under transmitted(? 2= 7.784 , P =0.005 3) to probands with ADHD-LD. No biased transmission of any allele and haplotype were found in families with probands of ADHD+LD. Conclusion: ADHD-LD and ADHD+LD are different at the level of HTR2C gene polymrohisms of C 759T and G 697C. HTR2C is related to ADHD-LD, while not related to ADHD+LD.