Answer:
i) The substances that nucleotides that are made up of sugar, phosphates and a nitrogen base are both DNA and RNA. Both are composed of a carbon ringed structure that is a sugar base with the only difference of -OH group that is absent in DNA and present in RNA, to this carbon ring phosphate diester bond helps in the attachment of nucleotide monomers, and nitrogenous base is attached to the ring at one of the carbon.
ii) RNA is single-stranded structure that is found thought the cell and has bases A, C, U and G. It can't be DNA, because DNA is double stranded helix with adenine, guanine, cytosine and thymine as their bases uracil is not present in DNA. The sugar of DNA lacks the hydroxyl group at 2' position of carbon atom. Both DNA and RNA has a base of a sugar, to which one of the four nitrogenous base is attached and one or two phosphate groups are attached.
iii) The shape of protein is effected by the sequence of amino acids. As through the central dogma of transcription and translation lead to the formation of proteins, any change in the gene would mislead to the production of transcript RNA, this mutated RNA will result in the formation of mutated proteins with change in one or more amino acids. Change in a single amino acid will lead to change in the shape or structure of protein that would ultimately change the function of that protein.