Homozygous is a word that refers to a particular gene that has identical alleles on both homologous chromosomes. It is referred to by two capital letters (XX) for a dominant trait, and two lowercase letters (xx) for a recessive trait.
Effects of Homozygous Genes
Following are some examples of homozygous genes.
- The dominant trait for eye color is brown, represented by BB. All other eye colors – blue, grey, green, and hazel – are recessive traits, represented by bb. A homozygous brown eyed person would have the BB gene, while a homozygous blue eyed person would have the bb gene.
- One person is immune to poison ivy, which is represented by the dominant PP trait; while another is not immune to poison ivy, which is represented by the recessive trait distinguished by the symbol pp.
- Having freckles is the dominant trait for melanin deposits on the cheeks and body. A homozygous freckled person would have the FF gene, while someone with the homozygous gene of the individual without freckles would be represented by ff.
- A full head of hair is a dominant feature, with the homozygous gene of HH. However, the recessive trait – baldness – can be manifested in an individual with the homozygous recessive gene, or hh.
- An individual has the dominant SS gene, a homozygous gene that results in farsightedness. However, his friend has the homozygous gene ss for the recessive trait, which is normal sight.
- One girl’s blood clots normally, so her homozygous gene is the dominant CC. A boy in her class has hemophilia, which is present in the recessive gene cc.
- Having dimples on the cheeks is a dominant trait, with the homozygous DD gene causing them. However, the recessive trait is distinguished by the symbol dd; individuals with this homozygous gene will not have freckles.
- Curly hair is a dominant trait, with the homozygous HH gene causing the condition. Its recessive trait, represented by the homozygous gene hh, is straight hair.
- The dominant trait for hearing and speaking is being able to speak normally, which is the result of the SS homozygous gene. However, an individual with the homozygous recessive trait, ss, is unable to speak or hear properly and is instead deaf and mute.
- An individual possesses normal vision due to the homozygous VV gene. On the other hand, his friend possesses the recessive vv gene, which results in his unfortunate colorblindness.
- One gentleman can bend his joints in funny ways because he possesses the dominant JJ gene for double-jointedness. Another gentleman does not possess this gene – instead, he has the recessive jj gene which means his joints bend normally.
- A boy is born with an extra finger on each hand due to the dominant gene EE, while another newborn with the recessive homozygous ee gene has the normal number of fingers on her hands.
- Unattached earlobes is a trait that is the result of a dominant gene UU, while an individual with the recessive homozygous gene (uu) actually has attached earlobes.
These examples of homozygous should give you a better understanding of chromosomes and genetics.