drd4 gene polymorphisms as a risk factor for children with …downloads.hindawi.com › journals ›...

Research ArticleDRD4 Gene Polymorphisms as a Risk Factor for Children withAttention Deficit Hyperactivity Disorder in Iranian Population

SeyedMahmoud Tabatabaei12 Shahrokh Amiri2 Sara Faghfouri2

Seyed Gholamreza Noorazar2 Shahin AbdollahiFakhim3 and Ali Fakhari2

1Department of Physiology Tabriz Branch Islamic Azad University Tabriz Iran2Research Center of Psychiatry and Behavioral Sciences Tabriz University of Medical Sciences Tabriz Iran3Department of Otolaryngology Head and Neck Surgery Tabriz University of Medical Sciences Tabriz Iran

Correspondence should be addressed to Shahrokh Amiri amirishtbzmedacir

Received 27 February 2017 Revised 13 April 2017 Accepted 23 April 2017 Published 24 May 2017

Academic Editor Pieter J Hoekstra

Copyright copy 2017 Seyed Mahmoud Tabatabaei et al This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

Background and Objective Dopamine dysfunction is known to be associated with attention deficit hyperactivity disorder (ADHD)Dopamine D4 receptor gene (DRD4) is one of the important genes in this pathway This study intended to investigate the variablenumber of tandem repeats (VNTR) in exon 3 of the DRD4 gene in Iranian children and adolescents Materials and Methods Inthis study 130 children with ADHD aged 6ndash14 years and 130 healthy children within the same age range were enrolled Allchildren were selected from northwest of Iran which have Caucasian ethnic background and are of a Turkic ethnic group VNTRpolymorphisms of the DRD4 gene were evaluated by PCR using exon 3-specific primers followed by agarose gel electrophoresisFindings The Hardy-Weinberg principle and Chi-square test showed a significant difference in 4-repetition (4R) alleles betweenthe ADHD (762) and control (538) groups (119901 = 0004 1198832 = 1739 df = 5) The least percentage of repetition alleles inboth groups was 2R Conclusion There is a significant correlation between the 4R alleles of DRD4 and ADHD in the northwest ofIran

1 Introduction

ADHD is a common childhood psychiatric disorder thatis associated with the symptoms of sustained hyperactivityimpulsiveness and inattentiveness The worldwide preva-lence is 4ndash8 in school-aged children which may persistduring adolescence and adulthood in 50ndash80 of cases [1] Acomparable prevalence is reported from Iranian populationand the rate is estimated to be 97 in children living in Tabrizcity [2]

ADHD is a heterogeneous neurobehavioral disorder withmultifactorial etiology leading to neural pathway alterna-tions [3] The phenotype is quite wide and includes impairedsocial functioning and skill acquisition and decreased cogni-tive abilities These increase the burden of undiagnosed anduntreated ADHDwith a significant impact on the career lifeand academic achievements [4 5]

Diagnosing ADHD is currently based on clinical simi-larities like other psychiatric conditions The diverse phe-notype results in diagnostic challenges [6 7] that should beaddressed by improvement of diagnostic methods Towardthis approach pharmacological studies animal models andbrain imaging all show the involvement of catecholaminepathways including neurotransmitters and related genes [8]Dopamine and norepinephrine are involved in neurologicalfunctions as well as attentiveness and awareness [8] Onthe other hand dopamine pathways are involved in motorcontrol and in controlling the release of various hormonesThese pathways and cell groups form a dopamine systemwhich is neuromodulatoryThemotor functions of dopamineare linked to a separate pathway with cell bodies in thesubstantia nigra that manufacture and release dopamineinto the dorsal striatum DRD4 gene that is expressed inseveral brain areas has also been investigated in relation to

HindawiInternational Scholarly Research NoticesVolume 2017 Article ID 2494537 5 pageshttpsdoiorg10115520172494537

2 International Scholarly Research Notices

ADHD [9 10] Linkage mapping shows the locus of thisreceptor gene on chromosome 11p155 [11] This gene hasseveral polymorphisms in its nucleotide sequence The 48-base pair variable number tandem repeat (VNTR) in exon IIIof DRD4 polymorphism is the most studied polymorphismin associationwithADHDBiologicalmolecular studies showthat this region couples to G-protein modulating cAMPproduction [12]

The length of exon III varies between 2 and 11 repeatsof a similar 48-bp VNTR presented by D42 to D411 [13]Typically these repetition alleles have two categories shortrepeat length allele (2ndash4 repetitions) and long repeat lengthallele (5ndash8 repetitions) [14]Meta-analysis shows that variants2 4 and 7 are far more common [15]

There are evidences supporting significant relationshipbetween 7-repeat alleles of DRD4 exon III polymorphism andADHD [16ndash19] On the other hand another group of studieshave reported a weak correlation between DRD4 and ADHD[20 21] However it is not well known if these negative resultsare due to the difference between groups and populationswith different race genetics and heterogeneity weaknessin performing and interpreting statistical tests or a realdifference between different societies As a result this studyaimed to investigate the relationship of DRD4 polymorphismwith ADHD in Iranian population

2 Materials and Methods

The present study was conducted in a child and adolescentpsychiatry clinic of TabrizUniversity ofMedical SciencesTheprocedure was approved by the regional ethical committeeand written informed consent was obtained from parents ofparticipated children and adolescents

3 Inclusion and Exclusion Criteria

The inclusion criteriawere children and adolescent aged 6ndash18years diagnosed with ADHD based on clinical interviewsconducted by a children and adolescent psychiatrist

The exclusion criteria were concurrent psychiatric disor-der epilepsy a serious medical condition or history of severetrauma and any degree of intellectual disability ADHD caseswith comorbid ODD andor CD were excluded

4 Participants

This study was conducted in northwest of Iran The popula-tions living in these areas have Caucasian ethnic backgroundand are of a Turkic ethnic group Children diagnosed withADHD (119899 = 130) in specialized psychiatric clinic wereincluded by a child and adolescent psychiatrist In this studyADHD diagnosis was carried out through a semistructureddiagnostic interview based on DSM-IV-IR criteria

A group of children (119899 = 130) who were introduced foradenotonsillectomy procedure within the same age rangewere taken as the controls These children were diagnosedto have no psychiatric condition by the same diagnosticprocedure as children with ADHD An informed writtenconsent was obtained from all parents

Table 1 Temperature plan used for proliferation of DRD4 exon III

Cycle number Stage Temperature DurationOne First denaturation 95∘C 5min

Thirty-fiveDenaturation 93∘C 20 secAnnealing 55∘C 20 secExtension 72∘C 30 sec

One Final extension 72∘C 7min

5 Instruments

51 Kiddie Schedule for Affective Disorders and Schizophrenia-Present and Lifetime Version (K-SADS-PL) This is a semi-structured diagnostic interview designed based on criteriadefined by the Diagnostic and Statistical Manual for MentalDisorders 4th edition (DSM-IV) This tool was to identifyADHD and possible comorbid psychiatric conditions as wellas choosing controls [22]

The diagnostic procedure was completed through inter-view with child and the parentsThe test-retest and interraterreliability of the Persian version is reported to be 081 and 069[22]

52 PCR-Variable Number of Tandem Repeats In his process2mL peripheral blood samples were prepared and genomicDNA was extracted from it using QIAamp DNA kit accord-ing to themanufacturerrsquos instructionThe extractedDNAwasquality-checked by using aNanoDropdevicewithin the rangeof 260ndash280 nmThe genotyping ofDRD4 exon III was carriedout by polymerase chain reaction with the following primersequences

(Forward) 51015840-GGTCTGCGGTGGAGTCTG-31015840

(Reverse) 51015840-GCGACTACGTGGTCTACT-31015840

Amplification by PCR was performed in 20120583L reactionmixture containing 50 ng genomic DNA using AmpliqonMaster Mix (Denmark) 1mL from each primer and02 120583LTaqDNApolymerase according to temperature plan inTable 1 PCR products were observed in agar gel (2) stainedwith ethidium bromide fluorescence under ultraviolet lightDigestion products were analyzed after agarose gel electro-phoresis

6 Statistical Analysis

Data from counting the gene products in each sample wasfed to SPSS21 Data are expressed as number and percentageand the obtainedmean values are investigated using the Chi-square test In this study 119901 lt 005was considered significant

7 Results

One hundred and thirty children diagnosed with ADHDand 130 children with no psychiatric diagnosis were enrolledMean age of children in the two groups was not significantlydifferent However there were more males in the ADHDgroup (83 in the ADHD versus 61 control group) Therole of a first-degree family relationship was present in many

International Scholarly Research Notices 3

Table 2 Demographics of the study sample

Index ADHD (119899 = 130) Control (119899 = 130) 119901 valueAge (year) 6883 plusmn 227 698 plusmn 250 03Gender (boygirl) 10822 8446 lt0001Percentage of ADHD boys 83 61 004Children of first-degree family marriage () 56 4 lt0001

Table 3 Frequency of variable number of tandem repeats (VNTR) in exon 3 of the DRD4 gene in Iranian children

Number of repeats ADHD group Control group119901 value

Number Percentage Number Percentage2R 3 23 9 69 gt0053R 4 31 16 123 gt0054R 99 762 70 538 00045R 9 69 12 92 gt0056R 8 62 11 85 gt0057R 7 54 12 92 gt005

samples Descendants of a cousin marriage accounted for themajority of children with ADHD (Table 2) As the resultsshow the parents of ADHD children had a significantlyhigher proportion of first-degree relatives Perhaps its cause isthat there was a different pattern than the multifactorial pat-tern for this disorder The study of pedigrees shows single-gene inheritance pattern that is why the frequency of child-ren with consanguineous marriage (especially the first cous-ins) was more than the control group

Table 3 shows the frequency of VNTR DRD4 in theADHD and control groups The Hardy-Weinberg principleand Chi-square test showed a significant difference in 4Ralleles between the ADHD (762) and control (538)groups (119901 = 00041198832 = 1739 df = 5) There was no signifi-cant between-groups difference in other repetitions The 2Rgenotype had the lowest prevalence

8 Discussion

ADHD is a prevalent neurobehavioral disorder startingduring childhood [23] According to several meta-analysisstudies genes involved in dopaminergic pathway specificallyDRD4 have an important role in pathogenesis of ADHD [16ndash18] There is no available study on the relationship of thistopic in Iranian population and this study was conducted touse repetitions of this gene as a biomarker for facilitating thediagnosis of this disorder in children

In the present study the DRD4 gene was observed in allIranian participants (ADHD and controls) within the rangeof 2R to 7R alleles The dominant alleles in our study were4R 5R and 6R among which the 4R allele had the highestprevalence The between-groups difference was significantonly in 4R allele Results of the present study are consistentwith those of Bidwell et al [19] Cheuk et al showed thatthe 4R allele had the highest frequency (84) among theirresearch population in addition this genotypewas correlatedwith presence of ADHD [24]

Though these studies were in line with the present studyconsidering 4R as an indicator of ADHD studies on otherpopulations specifically White Europeans and Americansshowed a greater role of 7R alleles in the development ofADHD [25] In contrast our study did not show any signifi-cant relationship between 7R alleles and ADHD

Another meta-analysis study showed a significant differ-ence in the relationship of ADHD and DRD4 7R in peopleof European-Caucasian and South American descent versuspeople of Middle Eastern Populations [26] Leung et alreported a very low prevalence of 7R alleles among Asianswhereas 4R had higher prevalence among them [27] Thisreport is consistent with the findings of our study

According to demographic and ethnicity studies it can beconcluded that phylogenetics can be studied by investigatingthe polymorphism of genes in specific diseases As it is seen4R is more prevalent in Asians than White Caucasians andEuropeans [14] High prevalence of 4R reported by Shahin etal in Egypt [25] as well as our study confirms this finding

However there are studies that refuse the relationship of7R alleles with ADHD Carrasco et al reports a negative rela-tionship between 7R alleles and ADHD in a study conductedon a Chilean population [28] Brookes et al in a study inTaiwan reported no relationship between DRD4 biomarkersand ADHD [29]

The most obvious explanation for dissimilarity ofreported results is differences of the study samples Howeverdiagnostic procedure and methodological differences shouldalso be accounted The importance of a conclusion is notrestricted to facilitating the diagnostic procedure but alsomight lead to preparing a precise treatment plan for eachindividual Functional differences in the DRD4 intracellularsignaling system have been studied for the 48-bp repeatalleles and studies show that the 7R allelemay be less sensitiveto endogenous dopamine and mediates a blunted responseto dopamine [12] If results of the present study replicatein further studies they might indicate good therapeutic


response and better prognosis of ADHD in northwest ofIran

It can be stated that the 4R allele carriers which appearfrequently in the ADHD patients in the northwest of Iranmay have a better prognosis than the carrier 7R which inother populations have been linked toADHD In otherwordsthe 4R allele repeats in DRD4 gene can be considered as aprognostic diagnosis in ADHD disorder in this area of Iran

9 Conclusion

In contrast to the results of studies conducted on WhiteEuropeans and Americans in which 7R was the geneticindicator of ADHD our study showed 4R as the variant ofthis disorder in northwest of Iran

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

This study was supported by Research Center of Psychiatryand Behavioral Sciences Tabriz University of Medical Sci-ences The authors thank all participants of this study

References

[1] G A Stefanatos and I S Baron ldquoAttention-deficithyperactivitydisorder a neuropsychological perspective towards DSM-VrdquoNeuropsychology Review vol 17 no 1 pp 5ndash38 2007

[2] S Amiri A Fakhari M Maheri and A MohammadpoorAsl ldquoAttention deficithyperactivity disorder in primary schoolchildren of Tabriz North-West Iranrdquo Paediatric and PerinatalEpidemiology vol 24 no 6 pp 597ndash601 2010

[3] R A BarkleyAttention-Deficit Hyperactivity Disorder AHand-book for Diagnosis and Treatment Guilford Publications 2014

[4] J Biederman A F Arnsten S V Faraone A E Doyle T JSpencer T EWilens et al ldquoNew developments in the treatmentof ADHDrdquo Journal of Clinical Psychiatry vol 67 no 01 pp 148ndash159 2006

[5] D Wallis H F Russell and M Muenke ldquoReview geneticsof attention deficithyperactivity disorderrdquo Journal of PediatricPsychology vol 33 no 10 pp 1085ndash1099 2008

[6] L Culpepper and G Mattingly ldquoChallenges in identifying andmanaging attention-deficithyperactivity disorder in adults inthe primary care setting a reviewof the literaturerdquoPrimaryCareCompanion to the Journal of Clinical Psychiatry vol 12 no 62010

[7] AMHamed A J Kauer andH E Stevens ldquoWhy the diagnosisof attention deficit hyperactivity disorder mattersrdquo Frontiers inPsychiatry vol 6 article 168 2015

[8] A M Reiersen and A A Todorov ldquoAssociation between DRD4genotype and autistic symptoms in DSM-IV ADHDrdquo Journal ofthe Canadian Academy of Child and Adolescent Psychiatry vol20 no 1 pp 15ndash21 2011

[9] S B Floresco and M T Tse ldquoDopaminergic regulation of inhi-bitory and excitatory transmission in the basolateral amygdala-prefrontal cortical pathwayrdquo Journal of Neuroscience vol 27 no8 pp 2045ndash2057 2007

[10] D Noaın M E Avale C Wedemeyer D Calvo M Peperand M Rubinstein ldquoIdentification of brain neurons expressingthe dopamine D4 receptor gene using BAC transgenic micerdquoEuropean Journal of Neuroscience vol 24 no 9 pp 2429ndash24382006

[11] J Gelernter J L Kennedy H H M van Tol O Civelli and KK Kidd ldquoTheD4 dopamine receptor (DRD4)maps to distal 11pclose to HRASrdquo Genomics vol 13 no 1 pp 208ndash210 1992

[12] J N Oak J Oldenhof and H H M Van Tol ldquoThe dopamineD4 receptor one decade of researchrdquo European Journal ofPharmacology vol 405 no 1-3 pp 303ndash327 2000

[13] J Wu H Xiao H Sun L Zou and L-Q Zhu ldquoRole ofdopamine receptors in ADHD a systematic meta-analysisrdquoMolecular Neurobiology vol 45 no 3 pp 605ndash620 2012

[14] ZHawiMMcCarron A Kirley G DalyM Fitzgerald andMGill ldquoNo association of the dopamine DRD4 receptor (DRD4)gene polymorphism with attention deficit hyperactivity dis-order (ADHD) in the Irish populationrdquo American Journal ofMedical Genetics - Neuropsychiatric Genetics vol 96 no 3 pp268ndash272 2000

[15] H H Tol C M Wu H Guan et al ldquoMultiple dopamine D4receptor variants in the human populationrdquoNature vol 358 no6382 pp 149ndash152 1992

[16] I R Gizer C Ficks and I DWaldman ldquoCandidate gene studiesof ADHD a meta-analytic reviewrdquo Human Genetics vol 126no 1 pp 51ndash90 2009

[17] D Li P C Sham M J Owen and L He ldquoMeta-analysisshows significant association between dopamine system genesand attention deficit hyperactivity disorder (ADHD)rdquo HumanMolecular Genetics vol 15 no 14 pp 2276ndash2284 2006

[18] A Nikolaidis and J R Gray ldquoADHD and the DRD4 exon III 7-repeat polymorphism An international meta-analysisrdquo SocialCognitive and Affective Neuroscience vol 5 no 2-3 Article IDnsp049 pp 188ndash193 2009

[19] L C Bidwell E G Willcutt M B McQueen et al ldquoA familybased association study of DRD4 DAT1 and 5HTT and con-tinuous traits of attention-deficit hyperactivity disorderrdquoBehav-ior Genetics vol 41 no 1 pp 165ndash174 2011

[20] C Marino R Giorda L Vanzin et al ldquoNo evidence forassociation and linkage disequilibrium between dyslexia andmarkers of four dopamine-related genesrdquo European Child andAdolescent Psychiatry vol 12 no 4 pp 198ndash202 2003

[21] S Johansson H Halleland A Halmoslashy et al ldquoGenetic analysesof dopamine related genes in adult ADHD patients suggestan association with the DRD5-microsatellite repeat but notwith DRD4 or SLC6A3 VNTRsrdquo American Journal of MedicalGenetics Part B Neuropsychiatric Genetics vol 147 no 8 pp1470ndash1475 2008

[22] A Ghanizadeh M R Mohammadi and A YazdanshenasldquoPsychometric properties of the Farsi translation of the kiddieschedule for affective disorders and schizophrenia-present andlifetime versionrdquo BMC Psychiatry vol 6 article 10 2006

[23] Subcommittee on Attention-DeficitHyperactivity Disorderand Steering Committee on Quality Improvement and Man-agement ldquoADHD clinical practice guideline for the diagnosisevaluation and treatment of attention-deficit hyperactivitydisorder in children and adolescentsrdquo Pediatrics vol 128 no5 pp 1007ndash1022 2011

[24] D K L Cheuk S Y H Li and V Wong ldquoExon 3 polymor-phisms of dopamine D4 receptor (DRD4) gene and attentiondeficit hyperactivity disorder in Chinese childrenrdquo American


Journal of Medical Genetics Part B Neuropsychiatric Geneticsvol 141 no 8 pp 907ndash911 2006

[25] O Shahin N A Meguid O Raafat R M Dawood M Dossand N G Bader El Din ldquoPolymorphism in variable number oftandem repeats of dopamine D4 gene is a genetic risk factorin attention deficit hyperactive egyptian children pilot studyrdquoBiomarker Insights vol 10 pp 33ndash38 2015

[26] A Nikolaidis and J R Gray ldquoADHD and the DRD4 exon III7-repeat polymorphism an international meta-analysisrdquo SocialCognitive and Affective Neuroscience vol 5 no 2-3 Article IDnsp049 pp 188ndash193 2009

[27] P W L Leung C C Lee S F Hung et al ldquoDopamine receptorD4 (DRD4) gene in Han Chinese children with Attention-DeficitHyperactivity Disorder (ADHD) increased prevalenceof the 2-repeat allelerdquo American Journal of Medical Genetics -Neuropsychiatric Genetics vol 133 no 1 pp 54ndash56 2005

[28] X Carrasco P Rothhammer M Moraga et al ldquoGenotypicinteraction between DRD4 and DAT1 loci is a high risk factorfor attention-deficithyperactivity disorder in Chilean familiesrdquoAmerican Journal of Medical Genetics - Neuropsychiatric Genet-ics vol 141 no 1 pp 51ndash54 2006

[29] K-J Brookes X Xu C-K Chen Y-S Huang Y-Y Wu andP Asherson ldquoNo evidence for the association of DRD4 withADHD in a Taiwanese population within-family studyrdquo BMCMedical Genetics vol 6 article 31 2005

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Advances in

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Volume 2014

Stem CellsInternational



Enzyme Research



Microbiology


ADHD [9 10] Linkage mapping shows the locus of thisreceptor gene on chromosome 11p155 [11] This gene hasseveral polymorphisms in its nucleotide sequence The 48-base pair variable number tandem repeat (VNTR) in exon IIIof DRD4 polymorphism is the most studied polymorphismin associationwithADHDBiologicalmolecular studies showthat this region couples to G-protein modulating cAMPproduction [12]

The length of exon III varies between 2 and 11 repeatsof a similar 48-bp VNTR presented by D42 to D411 [13]Typically these repetition alleles have two categories shortrepeat length allele (2ndash4 repetitions) and long repeat lengthallele (5ndash8 repetitions) [14]Meta-analysis shows that variants2 4 and 7 are far more common [15]

There are evidences supporting significant relationshipbetween 7-repeat alleles of DRD4 exon III polymorphism andADHD [16ndash19] On the other hand another group of studieshave reported a weak correlation between DRD4 and ADHD[20 21] However it is not well known if these negative resultsare due to the difference between groups and populationswith different race genetics and heterogeneity weaknessin performing and interpreting statistical tests or a realdifference between different societies As a result this studyaimed to investigate the relationship of DRD4 polymorphismwith ADHD in Iranian population

2 Materials and Methods

The present study was conducted in a child and adolescentpsychiatry clinic of TabrizUniversity ofMedical SciencesTheprocedure was approved by the regional ethical committeeand written informed consent was obtained from parents ofparticipated children and adolescents

3 Inclusion and Exclusion Criteria

The inclusion criteriawere children and adolescent aged 6ndash18years diagnosed with ADHD based on clinical interviewsconducted by a children and adolescent psychiatrist

The exclusion criteria were concurrent psychiatric disor-der epilepsy a serious medical condition or history of severetrauma and any degree of intellectual disability ADHD caseswith comorbid ODD andor CD were excluded

4 Participants

This study was conducted in northwest of Iran The popula-tions living in these areas have Caucasian ethnic backgroundand are of a Turkic ethnic group Children diagnosed withADHD (119899 = 130) in specialized psychiatric clinic wereincluded by a child and adolescent psychiatrist In this studyADHD diagnosis was carried out through a semistructureddiagnostic interview based on DSM-IV-IR criteria

A group of children (119899 = 130) who were introduced foradenotonsillectomy procedure within the same age rangewere taken as the controls These children were diagnosedto have no psychiatric condition by the same diagnosticprocedure as children with ADHD An informed writtenconsent was obtained from all parents

Table 1 Temperature plan used for proliferation of DRD4 exon III

Cycle number Stage Temperature DurationOne First denaturation 95∘C 5min

Thirty-fiveDenaturation 93∘C 20 secAnnealing 55∘C 20 secExtension 72∘C 30 sec

One Final extension 72∘C 7min

5 Instruments

51 Kiddie Schedule for Affective Disorders and Schizophrenia-Present and Lifetime Version (K-SADS-PL) This is a semi-structured diagnostic interview designed based on criteriadefined by the Diagnostic and Statistical Manual for MentalDisorders 4th edition (DSM-IV) This tool was to identifyADHD and possible comorbid psychiatric conditions as wellas choosing controls [22]

The diagnostic procedure was completed through inter-view with child and the parentsThe test-retest and interraterreliability of the Persian version is reported to be 081 and 069[22]

52 PCR-Variable Number of Tandem Repeats In his process2mL peripheral blood samples were prepared and genomicDNA was extracted from it using QIAamp DNA kit accord-ing to themanufacturerrsquos instructionThe extractedDNAwasquality-checked by using aNanoDropdevicewithin the rangeof 260ndash280 nmThe genotyping ofDRD4 exon III was carriedout by polymerase chain reaction with the following primersequences

(Forward) 51015840-GGTCTGCGGTGGAGTCTG-31015840

(Reverse) 51015840-GCGACTACGTGGTCTACT-31015840

Amplification by PCR was performed in 20120583L reactionmixture containing 50 ng genomic DNA using AmpliqonMaster Mix (Denmark) 1mL from each primer and02 120583LTaqDNApolymerase according to temperature plan inTable 1 PCR products were observed in agar gel (2) stainedwith ethidium bromide fluorescence under ultraviolet lightDigestion products were analyzed after agarose gel electro-phoresis

6 Statistical Analysis

Data from counting the gene products in each sample wasfed to SPSS21 Data are expressed as number and percentageand the obtainedmean values are investigated using the Chi-square test In this study 119901 lt 005was considered significant

7 Results

One hundred and thirty children diagnosed with ADHDand 130 children with no psychiatric diagnosis were enrolledMean age of children in the two groups was not significantlydifferent However there were more males in the ADHDgroup (83 in the ADHD versus 61 control group) Therole of a first-degree family relationship was present in many









8 Discussion











9 Conclusion




Acknowledgments


References







































Volume 201






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology









8 Discussion











9 Conclusion




Acknowledgments


References







































Volume 201






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology




9 Conclusion




Acknowledgments


References







































Volume 201






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology















Volume 201






















Advances in

Virolog y



Volume 2014




Enzyme Research



Microbiology

drd4 gene polymorphisms as a risk factor for children with …downloads.hindawi.com › journals ›...

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