martes, 11 de julio de 2017

Genetics of Earlobes

Genetics of Earlobes


Genetics of Earlobes

Similar to the human eyes, nose, and lips, the earlobes also have special features. Although the human ears look similar, there are minor structural differences that make each ear different from the other.
The major form of the gene that determines the shape of the earlobe is known as an allele. An allele is a gene which is found at a specific position on a chromosome. It has been established that all genes in our body have two copies; one from each parent.
Image Credit: Thiti Sukapan / Shutterstock
Image Credit: Thiti Sukapan / Shutterstock

Types of Earlobes

An earlobe is made up of connective tissues combined with a mixture of areola tissues and fat cells. Earlobes have a good blood supply which help in keeping them warm and maintaining balance. Majorly, there are two types of earlobes found in humans - free earlobes and attached earlobes.
Free Earlobes: Free earlobes are the most common form of lobes found. This type of earlobe is often large and hangs below the point of attachment to the head. This happens due to the influence of a dominant allele. If the genes from the parents get expressed by the dominant allele, then the child will be born with free earlobes.
In most cases, the allele is regnant to the free lobes compared to attached lobes. The free earlobe parents can also give birth to an attached earlobe child, depending on the reaction of the allele gene. If parents with free earlobes give birth to a baby with attached earlobes, it is certain that both of them had both a copy of the dominant and recessive allele.
Attached Earlobes: These types of earlobes are not rare, but are also not commonly found. Earlobes of such type are small in size and do not have hangs. They are attached directly to the side of the head. The structural formation of this kind of lobe is due to the absence of the dominant allele in the chromosomes. The recessive allele is expressed instead in the chromosomes to form an attached earlobe. It is not necessary that parents with attached earlobes should give birth only to the attached earlobe child.
Traits are the major factors that result from chromosome pairs and which, in turn, determine one’s overall physical appearance. When alleles combine, some exert ‘stronger’ influence down sythan the others. The stronger allele is responsible for the dominant traits. Dominant alleles are said to be found throughout an organism. If the dominant allele fails to show its presence, the recessive allele will be expressed. These are known as recessive traits.
Although the traits vary, the size of the earlobes for both the traits remain the same. An average man’s ear measures 6cm, while for a woman it is about 5cm, in which the earlobe size measures about 2cm.

Genetic Diseases and Earlobes

Genetic conditions play an important role in the birth of a human being. People born with abnormal growth of organs are considered to be affected by the traits before their birth. The major conditions that cause irregular or abnormal growth include:
  • Down’s syndrome: Down’s syndrome is a condition caused due to the presence of an extra chromosome; generally, a person has 46 chromosomes, but people with Down’s syndrome have 47 chromosomes. The extra chromosome may influence the growth and development of the body. People with this syndrome tend to have large ears, a small neck, and a flat face. Down’s syndrome cannot be cured, but the affected person can grow in a healthy manner without any trouble.
  • Turner syndrome: Only females are affected by Turner syndrome, and it is said to be a rare condition. It is a state wherein the female tends to lose one of the X chromosomes. It is assumed that this chromosomal abnormality occurs due to an error in the parent’s reproductive cell. A person with this syndrome will have abnormal ears, eyes, skeletal structure, and even abnormalities of the kidney.
  • Beckwith-Wiedemann syndrome (BWS): Wiedemann syndrome is described as the modification that occurs in the genes of chromosome 11. It is an excessive growth disorder indicated by large body parts, enlarged tongue, earlobe creases, etc. The earlobe crease is a wrinkle in the earlobe, which occurs due to the trait that was passed genetically by the family. The wrinkle is created when the flow of blood is decreased in the ear. Currently, there is no method of treatment identified to cure ear creases.
Birth disorders may be minor or severe and may occur at any stage during pregnancy. Most disorders affect the baby while in the womb, before the formation of the organs; however, not all genetic defects are caused by the transfer of gene from the parents. In many cases, the baby may be born with genetic disorders that the parent’s gene does not contain. Some defects are considered to be harmless, while some may require prolonged medical treatment.
Last Updated: Jul 4, 2017

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