Question

The human genome contains a family genes that code for different forms of myosin, which are expressed in different cell types and hav somewhat different functionsWhere the sequence of each gene would you expect to see differences among them?

Done Chapter 14 Homework Assignment The human genome contains a family of genes that code for different forms of myosin, which are expressed in different cell types and have somewhat different functions. Where in the sequence of each gene would you expect to see differences among them? O regulatory and protein-coding regions protein-coding region only regulatory region only o no difference in any part of the gene

Answer 1

OPTION A- REGULATORY AND PROTEIN CODING REGIONS

The sarcomeric myosin heavy chain (MyHC)gene family consists of eight known isoforms, each encoded by separate genes exhibiting a complex pattern of spatial and temporal regulation .Of the eight isoforms, four are expressed in adult skeletal muscle: type I or slow MyHC and three fast isoforms, IIa, IId/x, and IIb. Greater than 90% of the MyHC in adult skeletal muscle is composed of these latter three gene products. The three adult fast MyHC isoforms are expressed in different types of skeletal muscle fibers that have different physiological characteristics, with IIA fibers being smaller, slower, and more oxidative; IIB fibers typically being the largest, fastest, and most glycolytic; and IID/X fibers falling between these extremes.

Of the three adult skeletal fast MyHC genes,. Several muscle-specific regulatory elements have been found within the proximal IIb promoter, including potential binding sites for the myogenic regulatory factors (MRFs), serum response factor (SRF), and myocyte enhancer factor-2 (MEF-2) (11-16). Overexpression of any of the four MRFs greatly increases IIb promoter construct activity in differentiated C2C12 myotubes, whereas gene transfer studies have demonstrated that an E-box just upstream of the transcription start site is necessary for high-level expression of the IIb gene in vivo. In addition, mutation of the proximal AT-rich element AT-1 abolishes MEF-2 binding and greatly reduces promoter activity .  members of the MRF and MEF-2 families of myogenic transcription factors appear to be necessary for high-level, muscle-specific expression of the MyHC-IIb gene.