Is my guess correct according to this sentence?

In all organisms; from human beings to bacteria and viruses, the genes, or units of heredity, are composed of nucleic acid.(original) {Pg 417}

Question:
I guess : If the original were to be more ideal to fit grammar, it should be :
In all organism from human beings to bacteria and viruses, to the genes, or to units of heredity, they are composed of nucleic acid.
Here, the "they" refers to the " all organisms from human beings to bacteria and viruses, to the genes, or to units of heredity".
(I hope you correct any mistakes I made in all my writing)

Question

Is my guess correct according to this sentence?

In all organisms; from human beings to bacteria and viruses, the genes, or units of heredity, are composed of nucleic acid.(original) {Pg 417}

Question:
 I guess : If the original were to be more ideal to fit grammar, it should be :
In all organism from human beings to bacteria and viruses, to the genes, or to units of heredity, they are composed of nucleic acid.
Here, the "they" refers to the " all organisms from  human beings to bacteria and viruses, to the genes, or to units of heredity".
(I hope you correct any mistakes I made in all my writing)

Answer

Dan is correct in his explanation. However, after “organisms” the punctuation should be a comma and not a semi-colon.

Answer

Sorry, the sentence is correct as it and your interpretation is not the same as the original.    Think of it like this. The main point of the sentence is:

In all organisms the genes are composed of nucleic acid.

There are two parenthetical clauses elaborating on parts of the sentence:

ORGANISMS (from human beings to bacteria and viruses)   i.e. it's describing which organisms, i.e. all of them.

GENES (or units of heredity)   i.e. it's describing what genes are.

Hope that helps. Sentences such as this with a lot of clauses can be hard to 'unpack'.  Sometimes it can be helpful to remove the clauses between commas and see what the main parts are.