What is Down Syndrome?

Credit: Newcastle Hospital

What is Down Syndrome? In short it’s an extra chromosome that an individual can possess that teaches you that you’re willing to accept any of your children in any which way, whilst showering them with unconditional love just as you’ve always dreamed. However, it is also really important that society can grasp a more accurate and scientific idea of what DS really is! I bet most people didn’t even realize there were 3 different types of DS? I didn’t. Not until my son was born. DS is a chromosomal condition that occurs in 1 in 800 babies. The first type is your most common Trisomy 21, good old fashioned, vanilla DS, the type most people normally associate with. The second is called Translocation. Translocation Down Syndrome can be either random or it can be genetic. Lastly, the third is called Mosaic Down Syndrome. I am going to try and explain each type of DS as accurately as I can; from my understanding so far. I feel it’s important for everyone to gather at least a basic understanding of DS. How else can you spread awareness about Down Syndrome if you’re not entirely sure what it is?

Complete Trisomy 21 Down Syndrome. 

Individuals usually have 46 chromosomes in each cell. Trisomy 21 occurs during cell division as a random event in early fetal development. During egg or sperm formation what often happens is that a pair of chromosomes (chromosome 21 in the case of DS) fail to separate. This is called nondisjunction. This means that when the embryo is formed that it now contains 24 chromosomes instead of your ‘typical’ 23 as the embryo has three copies of chromosome 21. In approximately 90% of Trisomy 21 cases the extra chromosome comes from the mothers egg. In 4% of T21 cases it comes from the fathers egg and in only 1% of cases it occurs just after fertilization as the embryo is growing. Complete T21 DS means that every single cell in that persons body contains an extra copy of chromosome 21. This type of DS is the most common type occurring in 94% of people with the syndrome.

Translocation Down Syndrome.

Translocation Down Syndrome most commonly affects individuals the same way as T21 DS. This type of DS is caused by rearranged chromosomal material. In this type of DS only part of an extra copy of chromosome 21 is within the cells instead of it being separate. The extra part of the chromosome attaches itself to another chromosome this means that the extra chromosome 21 part can attach itself to any other chromosome e.g. 13, 11 or 3. Approximately 4% of babies born with DS have Translocation Down Syndrome.
Whenever Translocation Down Syndrome is diagnosed the parents also have their chromosomes studied, this is most commonly done through a blood test. If only one parent comes positive as possessing Translocation chromosomes then the medical professional will know the baby inherited it from that parent. This means that the parent with the gene actually has a total of 45 chromosomes in each cell of their body. However, the parent with the gene doesn’t typically have DS as they are only missing a chromosome instead of having one extra. This parent is known as a ‘balanced Translocation carrier.’ Translocation is the only type of DS that can be genetic.

Mosaic Down Syndrome.

Mosaic Down Syndrome is the least common type of DS and the most rare occurring in only 2% of individuals with DS. Mosaic DS means that various cells have various genetic makeup. Mosaic Down Syndrome means that not all of the persons cells contain the extra copy of chromosome 21 and that they can have cells that contain at total of 46 or 47 chromosomes. This is also known as Chromosomal Mosaicism. To be able to identify what parts of the individual with Mosaicism are affected you would have to test every inch of that persons body. Mosaic DS often occurs in early cell fertilization after a ‘normal’ egg and sperm unite, during the division. It can also happen when during development if some cells lose an extra chromosome 21 that were present at conception. Individuals with Mosaicism can sometimes be misdiagnosed as having complete DS as only some cells from one part of the body are usually examined and studied. In some rare cases some people may not even realize they have Mosaicism as in very rare cases only one area of the body may be affected. Approximately 15% of people diagnosed with complete T21 DS are actually misdiagnosed and have Mosaic DS. Individuals can also have Translocation Mosaic Down Syndrome. Did you know that the oldest person with Mosaic DS was an elderly lady who lived to 83?

All individuals with DS will share some level of physical and intellectual characteristics. These will all vary and aren’t all the same. 1 in 10 children with DS may have ADHD or ASD. In the UK 1 in 100 people usually have ASD or ADHD, this means that based on statistics only 10 children with DS out of 100 people,with or without the syndrome,will maybe have some extra additional needs. Individuals with DS are usually have varying levels of health conditions, but, so do the ‘typical’ population. If we were all the same life would be boring! I am so glad I have a lovely little boy to keep me busy and entertained. I won’t list characteristics of DS because like I said they vary and I don’t want to create a misconcepted or stereotypical view for people with DS.just remember that just because someone has a ‘look’ doesn’t mean they do or don’t have a type of DS. I am still waiting on what type Theo has and look forward to finding out soon as I have found learning about genetics actually fascinates me. You learn something new everyday.

“Imperfection is beauty, madness is genius and it’s better to be absolutely ridiculous than absolutely boring.”



8 thoughts on “What is Down Syndrome?

      1. My son frankie was diagnosed with a heart defect at 22 weeks whilst I was pregnant but we didn’t know he had trisomy 21 till he was born I didn’t want the test I wasn’t bothered either way now hes here and he’s just undergone heart surgery last week at 6 month old he’s on the road to recovery now and done so well he has a fiesty little character already and everybody loves him and if somebody said to me if you had one wish would it be for him not to have it I’d say no its who he is and I eouldnthave him any other way can’t wait to watch him grow so excited for what lies ahead #trisomy21 #downssyndromerocks

        Liked by 1 person

      2. Couldnt agree with you anymore. I love Theo and I love his Down syndrome. If I could change anything it would be his health problems and societies views ! Xx


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