As you know, individuals with Down syndrome have similar physical characteristics. So how is it that chromosome variation can shape these distinctive physical traits?
this question Genetic Engineer Dilara SarıWe directed it to. Itself Instagram, twitter and YouTubeHe enlightens hundreds of thousands of people by sharing about genetic research, biological systems and scientific developments.
This time As a guest of Webtekno will enlighten many of our readers on an important genetic science. Here are our questions and Dilara’s answers:
Why do people with Down syndrome have 47 chromosomes instead of 46?
In individuals without any chromosomal abnormality, total 46 chromosomes 1 pair of these chromosomes are sex chromosomes. That is, there are 22 pairs of autosomal chromosomes. The condition of these chromosome pairs being triple instead of double is called trisomy. Down syndrome is usually a trisomy on the 21st chromosome, so it is not 46 in individuals with Down syndrome. 47 chromosomes exists.
There are different types of Down syndrome. What exactly are the differences between them?
Mosaic Down syndrome In the case of the first fertilization, while there are actually 46 chromosomes, some cells have 47 chromosomes due to an anomaly that develops later. Some cells of the person carry 46 chromosomes and some cells carry 47 chromosomes. The regions where 47 chromosomes are most prominent are the regions most affected by the syndrome. For example, if 46 chromosomes are observed in the cells in the nervous system, not 47, the IQ level of the person will not be affected by the syndrome. can develop the same as their peers. If 47 chromosomes are observed in the muscular system, posture and speech disorders will be observed.
Translocation Down syndrome the rarest of the cases, 3% of form of Down syndrome. In other varieties, the extra chromosome/chromosome part is located next to the 21st chromosome pair, but in the case of translocation, this excess is free and adheres to the chromosome pair.
So what causes the similar physical appearance?
Cells contain extra genetic material. This material excess, as in other anomalies, specific It creates physical deformations and developmental problems and affects the external appearance of the individual.
For Down syndrome, the extra genetic material in this 21st chromosome creates a physical change by preventing the development of certain connective and bone tissues, especially in the head area. A small nose, mouth and ears, almond eyes, short neck, rounded head shape from the front, flat in the back (up from the nape), short nails, and white spots on the iris are the most noticeable physical features.
At the same time, these individuals are due to muscle movement problems. they are more prone to gain weight. In fact, individuals with Down syndrome all have different skin, hair and eye colors and are different from each other. The fact that the excess of the 21st chromosome causes such changes, especially in the head region, causes all individuals with Down syndrome to resemble each other.
Mosaic affects in Down syndrome. on a cell and system basis We said there was change. In other words, individuals with Mosaic Down syndrome may have less physical symptoms compared to the normal and translocation type, and the symptoms vary depending on which system is affected. For this reason, their facial features may not resemble other Down syndrome individuals too much.
Thanks to Dilara Sarı for answering our question. You can also follow him on his social media accounts: Instagram | twitter | YouTube
Dilara will soon answer our other questions about genetics. Stay tuned…