Common Human Inheritable Traits and Pattern of Inheritance

These are some of the common dominant and recessive traits in humans that can be easily observed in people around you. You have two genes for them. One inherited from your father and one from your mother. The way that a physical trait is expressed, and hence the way you look is a result of either a combination of dominant genes, a dominant and a recessive gene or two recessive genes. hairline shape-v shaped (widows peak) or straight earlobe attachment-free ear lobes, attached ear lobes tongue rolling handedness cleft chin, Dimples, freckles, naturally curly hair hand clasping colorblindness

Hairline One example of a dominantly inherited trait is the presence of a widow’s peak(v shaped) at hairline. Straight hairline is recessive trait. (W) is the dominant allele, and (w) represent the recessive allele.  An individual with a (WW) or (Ww) genotype will have a V-shaped peak at the hairline. Only ww individuals will have a straight hairline.  Genotype (1:2:1) - 1 Homozygous dominant - 2 Heterozygous - 1 Homozygous recessive Phenotype (3:1) - 3 V shaped hairline,1 straight hairline

Earlobes Free ear lobe is dominant (E). Attached earlobe is recessive (e). (E) is the dominant allele, and (e) represent the recessive allele.  An individual with a (EE) or (Ee) genotype will have free earlobes.. Only (ee) individuals will have attached earlobes. Genotype (1:2:1) - 1 Homozygous dominant - 2 Heterozygous - 1 Homozygous recessive Phenotype (3:1) - 3 free earlobes, 1 attached E e EE Ee ee

Tongue Rolling One example of a dominantly inherited trait is the presence of the ability to roll your tongue. The tongue-rolling version is dominant over the one that doesn't let you roll your tongue (T) is the dominant allele, and (t) represent the recessive allele.  An individual with a (TT) or (Tt) genotype can roll their tongue. Only tt individuals cannot roll the tongue. There are many examples of parents who can't roll their tongues having tongue-rolling children. Tongue rolling is not a simple dominant trait.

Handedness Like many complex traits, handedness does not have a simple pattern of inheritance. Children of left-handed parents are more likely to be left- handed than are children of right-handed parents. However, because the overall chance of being left-handed is relatively low, most children of left-handed parents are right- handed. Many twins have opposite hand preferences.

Cleft Chin, Dimples A cleft chin, also known as a dimpled chin, is a distinctive facial characteristic which is inherited. Dimples can be present on both cheeks or one. The genetics of dimples follows a dominant pattern of inheritance, that is to say that a child only needs to inherit one dominant gene for dimples to have them.  Draw Punnett square for both parents having dimples, father having dimples and mother doesn’t have dimples, both parents not having dimples. Freckles show a dominant inheritance pattern: parents who have freckles tend to have children with freckles.  Other genes and the environment influence freckle size, color, and pattern.

Punnet Square to determine Cleft chin heredity  

Naturally Curly Hair There are two versions of the hair type gene, curly (C) and straight (s). Hair type is an example of incomplete dominance. If you have one of each version of the gene, you get a mix of the two or wavy hair. So for hair type, CC gives curly, Cs gives wavy and ss gives straight hair.

Color Blindedness Traits that are determined by alleles carried on the X chromosome are referred to as X-linked. X-linked alleles require a specific notation: Xc  (recessive allele) or X+ (Dominant allele).  Females will have two X-linked alleles (because females are XX), whereas males will only have one X-linked allele (because males are XY).

Color Blindedness One example of an X-linked trait is red- green colorblindness. Females that are X+X+ or X+Xc have normal color vision, Females that have XcXc  are colorblind. Males that are X+Y have normal color vision XcY males are colorblind. (Xc) -recessive allele that causes colorblindness (X+)- the normal dominant allele.

Hand Clasping Most people place their left thumb on top of their right and this happens to be the dominant phenotype. Right thumb on top of left thumb is recessive.

References http://knowgenetics.org/dominant-inheritance/ http://thehappyscientist.com/science-experiment/ear-genes http://genetics.thetech.org/ask/ask125 https://ghr.nlm.nih.gov/primer/traits/handedness http://www.brighthub.com/science/genetics/articles/13998.aspx https://www.google.com/search?q=how+to+determine+pattern+of+inheritance+for+cleft+chin&biw=1920&bih=953&source=lnms&tbm=isch&sa=X&ved=0ahUKEwii5uio7cXSAhWG1IMKHSd9B1oQ_AUICCgB#imgrc=9odPT3uTRB2HRM:

http://genetics.thetech.org/ask/ask45 http://www.scienceprofonline.com/genetics/ten-human-genetic-traits-simple-inheritance-2.html http://knowgenetics.org/x-linked-inheritance/ http://learn.genetics.utah.edu/content/basics/observable/