Fragile X syndrome is an X-linked dominantly inherited condition that contributes

The probability for the given scenario will be 9/64

Explanation:

As indicated by the above expressed inquiry,  

Two people (i.e) male (hetero) + female (hetero)  

Prevailing + Latent = First Child  

Latent + Dominan = Second Child  

Latent + Passive = Third Child  

The probability of gene communicating will be low than initial two children.The coding succession is called codons..There are 64 codons for each 3 grouping one amino-acid will be produced.The likelihood of prevailing gene will be 9.  

So the appropriate response is 9/64.

different allele forms of a trait