Sample Psychology Essay Paper on Dominant–Recessive Inheritance

Dominant–Recessive Inheritance

Introduction

Dominant-recessive inheritance is an important concept used to predict the possibility of an individual inheriting a phenotype from the parent. Dominant alleles are responsible for producing dominant phenotypes in individuals who have only one copy of the alleles while recessive alleles only produce a recessive phenotype when the individual have two copies of the allele, one from each parent. There are individuals who are carriers, they possess one dominant and one recessive but only have the dominant phenotype, as the recessive phenotype is not present.

            The dominant allele shows its effect even when the individual has only one copy a condition described as heterozygous but for the recessive allele the individual must have two copies of the allele, this condition is a case of homozygous. Examples are the alleles for dimples, brown eyes are dominant but the allele for blue eyes, and no dimples are recessive. This example illustrates the dominant-recessive inheritance of dimples. For illustration purpose, a dominant trait when a person has dimples is represented by a capital letter “D” while a lower case letter as “d” gives the recessive trait, no dimples

            Where, D= dominant dimple allele, d=recessive allele no dimple, Dd= dimples, dd= no dimples, and DD= dimples. The following chart shows possible combinations.

Dominant- dominant alleles cross   D D D DD DD D DD DD  
 Carrier-Carriers alleles cross   D d D DD Dd d Dd dd  
Recessive-recessive alleles cross   d d d dd dd d dd dd  
Dominant-recessive alleles cross   D D d Dd Dd d Dd Dd  
Carrier- recessive alleles cross   D d d Dd dd d Dd dd  
Carrier-dominant alleles cross   D d D DD Dd D DD Dd