Yes, a single strand of DNA can function as both a sense and antisense strand in different contexts, coding for distinct proteins. This reflects the complexity of gene organization and expression within the genome.
Can the same strand of DNA act as a sense strand and an antisense strand at two different occasions of transcription and result in two different proteins? Yes, the same strand of DNA can indeed serve as a sense strand for one gene and as an antisense strand for another gene at different instances. This property reflects the complex organization and regulation of genes within the genome.
Each strand of DNA may contain several regions that code for proteins, known as genes. During the process of transcription, a particular segment of DNA is copied into messenger RNA (mRNA). The strand of DNA that is used as the template for RNA synthesis is the antisense strand, while its complement, which has the same sequence as the mRNA (except for thymine being replaced by uracil), is known as the sense strand. The complementarity of bases means that the mRNA has a sequence identical to the sense strand, though with uracil replacing thymine.
Due to the versatility of DNA, it is possible for overlapping genes to exist, where one strand of DNA may be transcribed in one direction encoding a certain protein, and the same strand may be transcribed in the opposite direction in a different region, encoding a completely different protein. This may happen under different physiological conditions, in different cells, or at different times. The phenomenon where one DNA strand serves both functions is termed 'bifunctional DNA.'