What causes low intelligence in individuals with Down syndrome?
Have you ever wondered why adults with Down syndrome display mental capacities similar to those of 8- or 9-year-old children? How does having an extra chromosome significantly impact IQ levels? Let’s dive into the science behind this fascinating phenomenon.#DownSyndrome #LowIntelligence #ExtraChromosome #IQLevels
Understanding Down Syndrome and IQ Levels
Exploring the Link Between Genetics and Intelligence
– How does the presence of an extra chromosome affect cognitive abilities?
– What research has been conducted to study the connection between Down syndrome and low intelligence?
Factors Influencing Cognitive Development
Environmental and Genetic Contributors
– How do environmental factors play a role in the intellectual development of individuals with Down syndrome?
– What genetic mechanisms contribute to variations in IQ levels among people with the condition?
Addressing Misconceptions About Intelligence
Dispelling Myths and Stereotypes
– What misconceptions exist about the intelligence of individuals with Down syndrome?
– How can we promote a better understanding of the capabilities and potential of people with this genetic condition?
Also interested in this. My suspicion is that the extra chromosone fucks with the brain’s development in some way.
I don’t know the mechanism behind it but I did recently learn that both physical issues as well as mental capabilities can apparently vary wildly between different individuals with down syndrome. Some can have basically no learning difficulties while others can have quite severe ones. It really depends. Just thought id put it out there as on a practical level it’s always good to know you shouldn’t assume. 🙂
Having an extra copy of a chromosome means you have extra copies of all the genes on that chromosome. When you have an extra copy of a gene that codes for a protein, cells may end up producing too much of that protein, resulting in deleterious effects. The following article specifies some proteins coded for by genes found on chromosome 21 in humans that adversely affect neurons in various ways when they are overexpressed in mice (no link because when I included the link, my post was removed):
Abukhaled, Y., Hatab, K., Awadhalla, M. *et al.* Understanding the genetic mechanisms and cognitive impairments in Down syndrome: towards a holistic approach. *J Neurol* **271**, 87–104 (2024).
Humans are a little complicated. You can almost* think of having an extra chromosome like writing two versions of software to do the exact same thing. Sure, sometimes the program can run fine, but sometimes some processes get broke and the whole thing doesn’t work correctly because they interfere with each other.
People with down syndrome have an extra copy of chromosome 21, which is also known as trisomy 21. This extra genetic material *seriously* disrupts how the brain and body normally develop, leading to distinctive physical features and intellectual disabilities. It can wind up effecting the structure of the brain, such as the size and even the connections it has internally.
Additionally, the presence of this extra chromosome can interfere with the production of proteins and other essential molecules crucial for brain development and function. These disruptions can affect various cognitive abilities like learning, memory, and communication skills.
As I somewhat noted earlier with the computer example, not all individuals with down syndrome will experience the same level of intellectual disability. The range can vary widely, from mild to moderate to severe. There are *many* factors that go into how they develop in the end, such as early intervention, supportive environments, and access to educational/therapeutic resources, but even then there’s only so much you can do for something that physically alters the brain and how it works.
I’ve always found it to be a bit strange to compare the capacity of people with cognitive or developmental delay with children of a certain age.
The example here is comparing adults with DS with normal 8-9 year olds who are usually physically coordinated and capable, have a massive capacity to learn socially and academically, and have reasonable extensive vocabularies.
I get the comparison to a degree, but I’ve always thought it was apples and oranges.
There is a gamut of intelligence with Down’s syndrome. Not always 8 or 9.
I work with people with developmental disabilities and it’s not really accurate to say this about all people with Down syndrome. Some are pretty high functioning and some are very low functioning. I work and have worked either people of every extreme. I think science doesn’t really know “why,” just that cognition is affected.
I had a really high IQ when I was 9. If anything, my mental capacity right now is much worse.
Actually, the fact that an extra chromosome *only* produces Down syndrome, and not a more severe phenotype, is what is surprising!
With most other chromosomes, beside #21 (and beside extra X or Y), a trisomy (3 copies instead of 2) will disrupt development so severely that it is incompatible w life.
That is, those embryos usually die, some in the embryo stage and some later in fetal development. A couple trisomies (18 and 13) produce severely malformed newborns that then die typically as babies.
https://www.childrenshospital.org/conditions/trisomy-18-and-13
I think the better question is how can a fetus with fucked up chromosomes even survive and develop into a somewhat functional human. There are other chromosome defects that will lead to death even before birth. It’s really a miracle people with down syndrome can even have cognition and get a chance at life to begin with.
Chromosomes are the cell’s condensed DNA, its blueprint so to speak.
Imagine having the blueprint for a building and every floor plan is correct – except for floor 21, which is 50 percent bigger than any other one. If you still manage to build that building, which is gonna be a serious challenge in and of itself, it will pose serious issues afterwards, as you can imagine.
A lot of great answers here, but just wanted to add that there are many people with Down’s syndrome that have average intelligence!
Everyone has already done a better job explaining it than I could, but here are my two cents: Genes are what define us. A slight shift in one gene could mean everything. Seriously, genes are EVERYTHING. A miniscule change in one gene alters aspects of who we are.
One shift in a gene can mean living a full life or dying early of Huntington’s. It is the difference between having Sickle cell anemia, albinism, Dent’s Disease, and so much more. A change in the 23rd chromosome is what makes our (genetic) sex. Honestly, a slight change in a gene can easily mean life or death. Low IQ seems like a drop in the bucket to me.