Answer:a). mRNA is formed by copying a gene on one of the DNA strands
Explanation: Transcription is a process in which the nucleotide sequence in one strand of a double stranded DNA is converted to an mRNA. The genetic information in a DNA is copied into an mRNA. The mRNA produced is not the same with the DNA in base composition and sequence rather the mRNA is complementary to the DNA strand. In DNA, adenine, guanine, cytosine and thymine are found but in the mRNA adenine, guanine, cytosine and Uracil are found. In mRNA base pairing, adenine pairs with uracil while guanine pairs with cytosine.
