Determining Paternity

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Information about Determining Paternity
Health & Medicine

Published on July 9, 2009

Author: LabTestGuru



This slideshow was created to show why determining paternity via physical traits is far from accurate and a dna paternity test is preferred.

Determining Patern Any Lab Test Now – Plano,Tx Ph: (972) 596-6181 Any Lab Test Now - Plano, TX 1

Introduction  Basic Genetics  Homozygous and Heterozygous  Dominant or Recessive Traits  Examples of Simple Inheritance of Traits that Show Complete Dominance  Using Simple Inheritance to Determine Paternity Any Lab Test Now - Plano, TX 2

Basic Genetics Few human traits are based on simple inheritance where one version of a gene (dominant allele) masks the expression of the other version of that gene (recessive allele). This article will discuss these traits and understanding their importance in determining paternity. Any Lab Test Now - Plano, TX 3

Homozygous and Heterozygous  How it relates to your aA gene with identical alleles for a single trait is said to be homozygous, and having different alleles is said to be heterozygous. For example, the gene for widows peak exists in two forms, one form or allele results in a V-shaped front hairline (W) and the other for straight front hair line(w).  A homozygous individual would contain the following alleles: (WW) or (ww). A heterozygous individual would contain the following alleles: (Ww). Any Lab Test Now - Plano, TX 4

Dominant or Recessive Traits  In cases of simple inheritance, where a characteristic is controlled by one pair of alleles and one allele is dominant over the other, this is called complete dominance. For that characteristic, an organism will have one of two phenotypes.  Using the previous example, an individual with a recessive phenotype (straight hairline) possesses a genotype consisting of two recessive alleles (ww).  An individual with the dominant phenotype (widow's peak) can be either homozygous(WW) or heterozygous (Ww). It is more difficult to know genotype when dominant allele is involved.  If both parents exhibit the dominant trait, their offspring have a 50-100% chance of inheriting the dominant trait. If only one parent has the dominant trait, there is a 50% chance that their offspring will have the dominant trait. If neither parent exhibits the dominant trait, there is no chance their children will have the dominant trait. Any Lab Test Now - Plano, TX 5

Examples  Cleft Chin  A prominent cleft in the chin is due to the bond structure which underlies the Y- shaped fissure of the chin. A cleft chin is the dominant phenotype due to the presence of the cleft gene. Females appear to be less conspicuously affected than males.  EXCEPTION: Scientists now say there are two genes involved in this phenotype. Thereby making it possible for two cleft chin parents to have a child without a cleft chin Any Lab Test Now - Plano, TX 6

Blue Eye Color  The blue eye color allele is recessive. This means that both genes must have both blue alleles i.e. "blue-blue", in a person with blue eyes. Parents with non-blue eyes can have offspring with blue eyes. However, two blue eyed parents have only blue eyed children.  EXCEPTION: There are cases of blue eyed parents having brown eyed children. One of the parents may be secretly be carrying a slightly mutated allele for brown eyes. Although the mutated brown eyed allele is silent in the parent, the child inherits the non-mutated version. Any Lab Test Now - Plano, TX 7

Dimples  A dimple is the outcome of a fault in the subcutaneous connective tissue that develops during embryonic development. Since the dimple gene is dominant, a child has dimples if the gene is present in him/her.  EXCEPTION: The dimple gene is dominant; however, it is not always expressed. Any Lab Test Now - Plano, TX 8

Earlobes  The dominant trait is for lobes to hang free, a bit of lobe hanging down prior to the point where the bottom of the ear attaches to the head. With the recessive phenotype, the lobes are attached directly to the head.  EXCEPTION: There are cases of people having one attached earlobe and one free-hanging. These cases show that free-hanging lobes aren't always expressed and earlobes can not be used to determine paternity. Any Lab Test Now - Plano, TX 9

Conclusion Typically, maternity is easy to determine. Unfortunately, there is no easy way to determine paternity. The obvious first method is to compare general physical appearance. Often inconclusive, the next method is to read about Mendelian genetics concerning simple inheritance, such as this article. It is extremely important to note that there are documented exceptions to every trait listed above. For example, it is possible for a particular gene to not be expressed and thereby not exhibit traits associated with it. This is the reason a DNA paternity Test should be the only method to determine paternity when doubt is present. Any Lab Test Now - Plano, TX 10

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