Final answer:
A gene is a sequence of DNA that during transcription is used to create a messenger RNA (mRNA) molecule, which is ultimately translated into a protein.
Step-by-step explanation:
A gene, in the context of transcription, is a sequence of DNA that encodes a protein or functional RNA. During transcription, the gene's DNA sequence is used as a template to produce a complementary messenger RNA (mRNA) molecule. This mRNA then leaves the nucleus and goes to the ribosome, where it is translated into a protein with a specific amino acid sequence, a process known as translation. The gene thus acts as the fundamental unit of heredity, carrying the instructions for the synthesis of proteins, which lead to the expression of our traits and characteristics.