Slide 1: 

Fragile X syndrome is the most common cause of intellectual disabilities that can be inherited.

Slide 2: 

It is caused by a change, or mutation,in a specific gene on the X chromosome.

Slide 3: 

This gene is called the Fragile X intellectual disabilities – one gene, or F-M-R ONE gene for short. 

Insert new slide:  

The F-M-R ONE gene is found in every cell of the body…

Slide 4: …

but the protein it makes is essential for normal brain development.

Slide 5:

In the case of fragile X syndrome, the F-M-R One gene either does not make this protein, or makes too little of it, and so the brain does not develop normally.

Slide 7:  

To understand the type of mutation that causes fragile X syndrome, we first need to understand some basic genetics.  DNA is made up of four chemical building blocks called nucleotides: 
Adenine, Cytosine, Guanine, Thymine. 




Slide 8: 

These four nucleotides are represented by their first letters: A-C-G-T. They are then strung together one after the other to make up a gene, 
such as the F-M-R ONE gene.

Slide 9: 

The gene acts like a set of instructions 
that tells the cell how to make a specific protein.

Slide 10: 

At the beginning of the F-M-R ONE gene, there is a section with the letters see-gee-gee that repeat over and over.  

Slide 11: 

In most people, the number of see-gee-gee repeats is small – between 6 and 44 repeats.  

Slide 12:

In other people, the see-gee-gee pattern repeats between 45 and 54 times.  This is called an intermediate repeat.  

Slide 13: 

And still other people can have the see-gee-gee repeat between 55 and 200 times.   This is called a premutation, but the protein is still produced and the brain develops normally.  

Slide 14: 

Fragile X syndrome occurs when there are more than 200 see-gee-gee repeats, which is also called a full mutation.  

Slide 15: 

The large number of see-gee-gee repeats results in the gene turning off…

Slide 16: 

…and no protein is made.  

Slide 17: 

This is the cause of 95% of the cases of fragile X syndrome.