Complex sentence: MODY 1 is due to a loss-of-function mutation in the gene on chromosome 20 that codes for HNF4-α protein also known as transcription factor 14 (TCF14).
Split into simpler sentences: MODY 1 is due to a loss-of-function mutation in the gene on chromosome 20. This gene codes for HNF4-α protein also known as transcription factor 14 (TCF14).