What was most likely a question that inspired Leeuwenhoek, Koch, and Petri as they developed new technologies while exploring germ theory? How can broken bones be healed more quickly?
How can scientists see germs more clearly and easily?
What makes some foods more dangerous?
What is the one medicine that can heal all diseases?

a "theory" a suggestion that is not 100 % accurate, or a figure. some people say its a theory because they of all the passed theory's about one subject. it depends sometimes theory might be accurate and sometimes they are.

the answer to the blank provided is “an autosomal gene that is required for the expression of genes on the x chromosome”.

testis-determining factor, abbreviated as td, which is more popularly known as sex-determining region y or sry protein, is a dna-binding protein or  gene-regulatory protein/transcription factor, encoded by the  sry gene. it is the gene responsible for the initiation of male gender determination in humans.