if a strand of DNA has the sequence ATGCGATCCGC, then the sequence of the MRNA molecule transcribed from it is​

DNA:      ATGCGATCCGC

mRNA:   UACGCUAGGCG

Explanation:

The deoxyribonucleic acid (DNA) is a double-stranded helix, where each strand is composed of four nitrogenous bases: Adenine (A), Thymine (T), Guanine (G) and Cytosine (C). The two strands are held together by hydrogen bonds and they interact in the following way: Adenine (A) always pairs with Thymine (T) through two hydrogen bonds, while Guanine (G) always pairs with Cytosine (C) through three hydrogen bonds. During transcription, a DNA strand of the double helix DNA molecule is used as template to synthesize a complementary RNA molecule, usually, a messenger RNA (mRNA) which is then used to create a protein by the process of translation. Moreover, also during transcription, Thymine (T) bases are replaced by Uracil (U) bases in the RNA molecule.

a "theory" a suggestion that is not 100 % accurate, or a figure. some people say its a theory because they of all the passed theory's about one subject. it depends sometimes theory might be accurate and sometimes they are.