Genotype, Transcription factors, Epigenetic mechanisms
Environmental effects can be seen in control of cell differentiation, altering genetic expression and holding them to their terminal form.
5' promoter region precedes DNA sequence for a gene. Determines whether mRNA transcription occurs. Transcription factors bind to the promoter section, Recruit RNA Polymerase.
Gene regulatory proteins bind to the gene enhancers, around the gene or within. Up/downregulate gene transcription. Dictate whether RNA polymerase will generate mRNA.
Multiple Transcription factors are responsible for control of gene transcription and control.
Condensation of the genome: Nucleosome 30nm chromatin and histone association. 8 histones/nucleosome. HISTONE tails are susceptible to chemical modification. We call these 'Tags'.
Chemical tags alter gene packaging; and transcription. Genes may be turned on/off independently of genetic sequence.
Dosage Compensation: Human XY Male, XX Female.
So, one X chromosome in females is Randomly Inactivated to balance allele expression.
Inactive X chromosome can be seen as densely stained mass - Barr body. Random inactivation between two, occurs early in development during blastocyst stage.
Inactive X is passed on to next cells, heritable epigenetic trait.
.doc S07 Clinical Imaging