Answer:
A. proteins, genetic
Explanation:
The changes in DNA sequence cause mutations as a result of which the protein which is produced from such altered DNA is also defective and may not function properly. Changed DNA sequence means changed amino acid sequence of the protein because it is DNA sequence which controls and directs the RNA molecules to incorporate a specific amino acid in the peptide chain during translation i.e. protein synthesis. Once a peptide chain has been synthesized it is bound to fold in a proper manner then only it can be functional otherwise it may not function accordingly. But, changes in the sequence of amino acids may cause misfolding of protein molecules leading to malfunctional protein.
Also, the diseases which occur due to defective DNA are known as genetic diseases because DNA is responsible for heredity i.e. passing of traits from one generation to another generation. So, if the parents have the disease then their children may also acquire the disease and rest of the individuals of the population will not be affected with that genetic disease. In contrast to this, a contagious disease is the one which is spread amongst individuals of a population because of proximity not because they are genetically related, it has nothing to do with heredity. Contagious diseases are usually caused by pathogens or a foreign molecule so all the options except for A option are incorrect.
