Certain food elements are called major elements because

it's diluted or concentrated

in a diluted solution, you can add a lot more solute but in concentrated only a little more can be added

synapse nervous system

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.