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6q - Deletion - An Overview

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6q deletion is a genetic disorder that is caused due to loss of genes from chromosome 6. Refer to this article for a detailed description.

Medically reviewed by

Dr. Mohammad Rajja

Published At November 25, 2022
Reviewed AtNovember 25, 2022

Introduction:

6q deletion is a genetic disorder caused due to absent or missing genes from chromosome 6. This disorder is caused due to a genetic error called deletion. The other names for 6q deletion are deletion 6q, monosomy 6q, 6q monosomy, and partial monosomy 6. Gene deletion in chromosome 6 ranges from small to large deletions. Therefore, the severity of symptoms of this disorder in large deletion is more in comparison to small deletion. Individuals suffering from this disorder have distinctive facial appearances, delayed growth, and intellectual abilities and are also retarded.

What Is Meant by Chromosomal Aberrations?

Chromosomal aberrations explain structural and numerical abnormalities. The chromosomal mutation is the other name for chromosomal aberration. Structural changes or abnormalities are called structural aberrations, and numerical changes or abnormalities are called ploidy changes or numerical aberrations. Structural aberrations comprise the errors in which a chromosome or gene segment is extra, lost, or located in another region (translocated). Chromosomal aberrations have been classified into four types, namely:

  • Deficiency or deletion.

  • Duplication.

  • Inversion.

  • Translocation.

What Is the Deletion Type of Chromosomal Aberration?

Deletion is a type of chromosomal aberration in which a segment of the chromosome and its genes are missing. Deletion is of the following four types namely:

  • Terminal Deletion: In this, the segment of chromosomes or genes is missing from the terminal part with a single break.

  • Intercalary Deletion: It describes the type of genetic error in which the segment of a chromosome or the genes are missing from the between. In such a kind of deletion error, two breaks in the segment can be identified.

  • Homozygous Deletion: It describes the loss of chromosome segments or genes from the homologous chromosome pair.

  • Heterozygous Deletion: It represents the loss of chromosomal segments or genes from any homologous chromosome pair.

As stated above, deletion is the type of genetic error in which loss of genetic material and loss of genes are associated with deleterious effects. This error is expressed with a range of signs and symptoms specific to every genetic disorder.

How Is 6q Deletion Caused?

  • 6q deletion disorder is caused due to deletion of genetic material in chromosome 6 in the distal part of the long arm q.

  • In most cases, the deletion of genetic material is noted in the terminal end of chromosome 6.

  • More significant deletion shows more complex features than smaller deletion errors. Multiple genes are lost in this type of genetic error.

  • At present, all genes are not studied. Researchers are working extensively on identifying the genes responsible for the disorder.

  • Chromosomes are present in the nucleus of a cell present in the entire body of an individual. They are responsible for distinct characteristics in every individual.

  • Each chromosome has two arms, one short and the other long. The short arm is denoted as p, and the long arm is denoted by the letter q.

  • The deletion of the genetic material generally occurs due to a spontaneous error and is mostly not inherited.

What Are the Clinical Features of the Genetic Disorder Due to Deletion Mutation?

The following are the most commonly reported general clinical features:

  • Delayed growth.

  • Altered development of speech.

  • Motor skills such as sitting and standing are affected, which causes difficulty in carrying out daily activities.

  • Attention-deficit hyperactivity disorder is a commonly noted feature in 11q deletion. It is a neurodevelopmental disorder diagnosed in childhood and continues up to adulthood. Children suffering from this disorder have difficulty concentrating, get easily distracted, and have delayed thinking abilities. They have difficulty learning alphabets, spelling, and mathematical tables.

  • Compulsive behavior, such as shredding papers, is expected to alter behavior in these children.

  • As seen in autism, impaired socializing skills are also noted in these children.

  • Few individuals also suffer from heart and kidney disorders.

The following are a few distinctive features reported in individuals suffering from genetic disorders due to deletion:

  • The back of the head appears to be flat.

  • Hypertelorism (widely spaced eyes are commonly noted).

  • The eyelid fold is slanted upward.

  • Eyebrows have a high arch appearance.

  • The midfacial region of the individual is generally flat in appearance.

  • A short nose and flat nasal bridge are characteristic features in these individuals.

  • Widened philtrum over the lips.

  • Small lower jaw.

  • Abnormally protruded lips.

  • Ears are malformed.

  • The palate has a high arch appearance.

The genetic disorders caused due to deletion errors, namely, 6q deletion, 11q deletion, and 9p deletion, portray more or less similar characteristics, including delayed growth, retarded intellectual status, and distinctive facial appearance.

Is 6q Deletion Disorder Inherited?

6q deletion disorder is not an inherited disorder, and it is caused due to genetic error. This occurs due to a random error during the reproductive cell's production of eggs and sperm or during early fetal development. Affected people have no history of a similar disorder in the past, but they may pass this chromosomal deletion to their children. Five to ten percent of individuals even inherit these chromosomal deletion errors from parents unaffected by 6q deletion disorder. These chromosomal abnormalities produce symptoms that are typical of this genetic error.

What Are the Management Protocols for 6q Deletion Disorder?

A definite treatment protocol is yet to be discovered. The doctors focus on providing symptomatic relief that eases these individuals' daily activities. Psychiatrists aim to reduce the symptoms of behavioral disorders and improve these individuals' socializing skills. Physiotherapists seek to improve the motor skills of these individuals. So that they can sit, stand, and walk without any secondary support or minimum assistance. Dental practitioners aim to improve individuals' oral hygiene so that the caries rate is reduced. Specialized doctors treat individuals with severe signs and symptoms, including heart and kidney disorders, with utmost care.

Conclusion:

6q deletion disorder is a rare genetic disorder caused due to deletion of genetic material in chromosome 6’s long arm q. The signs and symptoms vary widely; thus, clinicians should thoroughly examine the patients. Solid treatment and protocol are unavailable, but various research is going on in medical genetics to treat this disorder. Genetic mapping and targeted gene therapy are extensively studied for their application in diagnosing and treating rare genetic disorders like 6q deletion.

Frequently Asked Questions

1.

What Is Meant by 6q Deletion?

Chromosome 6q deletion is a genetic abnormality caused due to missing genetic copy, which is present in the short arm (q) of chromosome 6. The size and site where the deletion occurred, and also the type of genes involved, determine the type of clinical manifestations and their severity.

2.

Is the Occurrence of Chromosome 6 Deletion a Common Defect?

No, deletions of chromosome 6 rarely occur. Features of this clinical condition widely vary and include developmental delay, ocular defects, hearing abnormalities, and cardiac dysfunction.

3.

What Is Chromosome 6 Responsible For?

Chromosome 6 is responsible for several cellular activities, such as immunity, inflammatory action, and neuronal activities. Defects in chromosome 6 lead to various diseases such as infections, cancer, immune and inflammatory disorders, heart disease, and mental illnesses.

4.

How Many Base Pairs Does Chromosome 6 Have?

Chromosome 6 constitutes nearly 6 % of the human genome and contains the largest sequence chromosome to date. It contains 166,880,988 base pairs that comprise 1,557 genes along with 633 pseudogenes.

5.

Which Chromosome Determines the Color of the Hair?

Chromosome 16 (MC1R gene) codes for red hair. HERC2 gene located on chromosome 15 is responsible for acquiring brown to light dark hair color, and chromosome 6 (RPS6KA2 gene) codes for black hair color.

6.

Which Is the Rarest Chromosomal Disorder?

Wolf-Hirschhorn syndrome (WHS) is the most extremely rarest chromosomal disorder. It is caused by the genetic defect in chromosome 4 where the deletion (missing genes) occurs in its short arm. Clinically, it is manifested with abnormally wide-set eyes (ocular hypertelorism) along with a broad and beaked nose. The head is unusually small (microcephaly) with low-set malformed ears showing growth deficiency.

7.

What Happens in Chromosome 6 Deletion?

In chromosome 6 deletion, developmental delay in growth is seen. Some of its clinical features include intellectual disability, behavioral abnormalities, and defective facial features.

8.

What Is Partial Monosomy Syndrome?

Monosomy occurs when only one chromosome is present instead of two pairs, generally seen in diploid cells. When these cells have only one chromosome along with an incomplete portion of the second chromosome,  partial monosomy occurs. Monosomy or partial monosomy leads to genetic disorders like Turner syndrome or Cri du Chat syndrome.

9.

How Many Copies of Chromosome 6 Do Humans Have?

Chromosome 6 belongs to 23 pairs of chromosomes present in humans. Normally, individuals have two copies of each chromosome. Therefore, humans have two pairs of chromosome 6. Changes in the number of pairs lead to genetic defects.

10.

What Is Chromosome 6 Known For?

Chromosome 6 contains a group of genes responsible for immune response called the major histocompatibility complex (MHC) genes. The MHC genes contribute to the development of innate and adaptive immunity. These genes are known for expressing biocompatibility or tissue rejection during organ transplantation and tissue grafting.
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Dr. Mohammad Rajja
Dr. Mohammad Rajja

General Practitioner

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