A genetic Study to Darwin's tubercle trait of External ear in the Population of Salah Al –Dein and Kirkuk

A genetic study for the trait of Darwin's tubercle in two ways : first , on a sample consisted of 52 family from Tikrit city in governorate Salah AL-Dein and 125 individual from their sons and 63 family from governorate of Kirkuk and 188 individual from their   sons . Secondly , adoption of pedigree analysis method for seven families from governorate of Salah El-Dein and Kirkuk , which confirmed the darwin's tubercle trait is a genetic trait and the presence of tubercle is dominant absence . The results of  Presence Darwin's tubercle also revealed  different forms : Nodosity tubercle , Enlargement tubercle and Projection. The present study support the truth of single gene locus hypothesis for the inheritance of this trait , in spite of it record the presence of one offspring have darwin's tubercle between two parents do not have darwin's tubercle in one family. The results of the study distribution of phenotypic for the trait showed on a sample consisted of 1415  individual from the citizens of the governorate of Salah Al-Dein (920♂: 495♀) from the original samples (1446) , an elevated percentage of the presence tubercle among the males (99.2%) than the females (98.4%) . The percentage of presence tubercle in the whole population was (98.9%) . Concering the allelic frequency for the gene of darwin's tubercle, the D allele was observed a higher frequency than the d allele in the whole population of the governorate: 0.895, 0.105 for both of them respectively . Expected frequencies of the three genotypes of darwin's tubercle trait , revealed a prevalence of the homozygous (dominant) genotype DD over the homozygous (recessive) and heterozygous genotype in the population of the governorate: 0.801, 0.188, 0.011 for DD , Dd and dd respectively.