Genes are the basic unit of inheritance by which characteristics are passed on from one generation to another



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Genotype (1:2:1)

- 1 Homozygous dominant

- 2 Heterozygous



- 1 Homozygous recessive

  • Phenotype (3:1)

- 3 V shaped hairline,1 straight hairline

  1. 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



  1. 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.



  1. 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.

  1. 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 one or both cheeks. The genetics of dimples follows a dominant pattern of inheritance, 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






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