Lecture 7. Developmental Genetics PDF

Lecture 7. Developmental Genetics Darius Noel C. Minoza Department of Biological Sciences College of Arts and Sciences Visayas State University Lecture Objectives At the end of this lecture, the students will be able to: 1. Discuss differential gene action 2. Describe mechanisms of gene action in b...

Lecture 7. Developmental Genetics Darius Noel C. Minoza Department of Biological Sciences College of Arts and Sciences Visayas State University Lecture Objectives At the end of this lecture, the students will be able to: 1. Discuss differential gene action 2. Describe mechanisms of gene action in both prokaryotes and eukaryotes 3. Explain the control of genes in development What is Developmental Genetics? Studies the relationships between gene regulation and cell differentiation during development During development, a fertilized egg becomes an adult organism Development is a process of regulated growth Results from interaction of the genome with the cytoplasm and environment What is Developmental Genetics? Development ✔requires several gene actions, because the phenotype is the expression of the genotype ✔ involves programmed sequence of phenotypic events which are typically irreversible ✔ requires formation of different cell types ✔ all cells have identical genotypes ✔ regulatory events lead to different cellular phenotypes A. Differential Gene Action: The Basis of Cell Differentiation After fertilization, ✔ zygote undergoes embryogenesis ✔ active cell division happens ✔ different cell types are formed ❑ determination – cell makes an irreversible commitment to a specific developmental path ❑ differentiation – expression of the cell’s specialized role Initial cytoplasmic environment in the embryo is provided by the maternal genome. Cytoplasmic determinants trigger the switching on of genes. - Sequence of complex changing populations of cells Consider these points Properties of a differentiated cell reflects the activity of genes Cells exactly the same genotype A cell manifests only a fraction of its genes Genes and chromosomes are equally distributed Chemical environments of the genes differ Different chemical/physiological environments induce different sets of genes to be expressed Hence, differential regulation of gene function Consider these points Distinctions of differentiated cells could be due to, largely, different compositions of enzymes Because enzyme structure is coded for by the DNA, appearance of a protein = gene for such protein is active Qualitative differences in protein content in the cells = differences in the schedule of functioning genes Consider these points The final phenotype in the cell is the result of selective gene expression at several steps in cell metabolism ✔ Pre-transcriptional control ✔ Transcriptional control ✔ Translational control ✔ Post translational modification 1. Pre-transcriptional control Gene amplification ✔ observed in oocytes of some species and in certain embryonic cells 1. Pre-transcriptional control Condensation and decondensation of the chromatin 2. Transcriptional control Differential initiation 2. Transcriptional control Differential splicing 2. Transcriptional control Differential splicing 2. Transcriptional control Differential splicing 2. Transcriptional control Selective pre-mRNA degradation 3. Translational control Selective translation 3. Translational control Stability of mRNA 4. Post translational modification Deletion of a part of the peptide chain 4. Post translational modification Changes in the Malate dehydrogenase state of oxidation or reduction affecting enzyme structure Lactate dehydrogenase 4. Post translational modification Sialic acid Attachment of a small molecular moiety of the enzyme Alkaline phosphatase 4. Post translational modification Polymerization and combination with phosphate groups Glycogen phosphatase