Answer:
Gene
Step-by-step explanation:
A GENE is the unit of inheritance in virtually the cells of all living organisms. It is a segment of DNA that codes for the ability to make one type of protein molecule. In other words, a gene encodes the synthesis of amino acids, which are building blocks of protein.
Genes are naturally found on chromosomes on which they undergo expression i.e. from gene - MRNA (transcription), from mRNA - protein (translation). Hence, based on the question asked, the segment of DNA that carries instructions for protein synthesis is called a GENE.