Lecture 7: Developmental Genetics

• Developmental Genetics - studies the relationship between gene regulation and cell differentiation
• Development - process of regulated growth that results from interaction of the genome with the cytoplasm and environment
• Differentiation - formation of different cell types, tissues and organs through specific regulation of gene expression
• 2 important stages in formation of different cell types: determination and differentiation
• Determination - irreversible commitment to follow a specific developmental path
• Differentiation - expression of a cell’s specialized role
• embryogenesis - active cell division (mitosis) and formation of different cell types
• Determinants - cytoplasmic effector substances that cause cells irreversibly committed to perform a specialized function
• Specialized cells - cells producing specialized proteins derived from luxury genes
• rbc - hemoglobin
• beta cells of pancreas - insulin
• initial cytoplasmic environment is set by maternal genome
• when cell divides cytoplasmic environment of each cell will be different from each other
• formation of diff. cellular phenotype is due to the unequal distribution of cytoplasmic environment w/c triggers differential gene action
• cell phenotype is a consequence of differential gene action or selective expression of its genes.
• pre transcriptional - selective DNA replication
• selective DNA replication - gene amplification
• pre transcriptional - condensation and decondensation of chromatin
• chromatin is highly condensed - INACTIVE (heterochromatin)
• chromatin is decondensed - ACTIVE (euchromatin)
• highly methylated DNA - inactive
• less methylated DNA - ACTIVE
• transcriptional control - differential RNA synthesis
• transcriptional control - differential initiation
• differential initiation - if gene has two or more TATA boxes
• transcriptional control - differential polyadenylation
• differential RNA processing - differential splicing
• transcriptional control - differential RNA processing
• Translational Control - selective translation
• translational control - stability of mRNA
• stability of mRNA depends on the length of poly A tail
• post translational control - modification of protein
• post translational - deletion of part of polypeptide
• post translational - change in the state of oxidation and reduction
• post translational control - attachment if small residue
• post translational - polymerization