Download Common Traits

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.
E
e
E
EE
Ee
e
Ee
ee
Genotype (1:2:1)
- 1 Homozygous dominant
- 2 Heterozygous
- 1 Homozygous recessive
Phenotype (3:1)
- 3 free earlobes, 1 attached
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 lefthanded 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 righthanded.
▪ 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 redgreen colorblindness.
▪ Females that are X+X+ or X+Xc have normal
color vision,
▪ Females that have XcXc are colorblind.
(Xc) -recessive allele that
causes colorblindness
(X+)- the normal dominant
allele.
▪ Males that are X+Y have normal color vision
▪ XcY males are colorblind.
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+f
or+cleft+chin&biw=1920&bih=953&source=lnms&tbm=isch&sa=X&ved=0ahUK
Ewii5uio7cXSAhWG1IMKHSd9B1oQ_AUICCgB#imgrc=9odPT3uTRB2HRM:
• http://genetics.thetech.org/ask/ask45
• http://www.scienceprofonline.com/genetics/ten-human-genetictraits-simple-inheritance-2.html
• http://knowgenetics.org/x-linked-inheritance/
• http://learn.genetics.utah.edu/content/basics/observable/