Question

consider two genes. Gene A is expressed in the liver and Gene B in the heart. if you are looking at DNA frim the liver, explain how gene A and gene B would be different at the chromatid level?Anwser needs heterochromatin, euchromatin nucleosome, histone acetyl transferase and histone deacetyolase and Which Gene is active and inactive

Answer 1

Since GeneA expresses in liver but not in heart means this gene is facultative heterochromatin because it is active in one tissue not in other this is because of the favorable condition for the expression of the gene. As in liver it expresses so in the liver it is the part of euchromatin nucleosomes while in the heart it is in heterochromatin.

if we talk about the activity of Histone Acetyl Transferase (HAT) it add the acetyl group to the lysine of the side chain of the histones make them loosen. so now the DNA is loosened as compare to the earlier state which helps in ease of the transcription while histone deacetylase has just opposite work of HAT, this makes gene inactive so it inhibits transcription. so in the liver may be HAT enzyme works for gene A while in heart histone deacetylase works for gene A. so gene A is transcriptionally active in the liver not in the heart

similar case for the gene B as it is in euchromatin in the heart but in liver ( heterochromatin state). HAT works for gene B in the heart while histone deacetylase works for gene B in the liver which makes gene transcriptional inactive. so gene B is transcriptionally active in the heart not in liver