BIOLOGY 116 Study Guide - Midterm Guide: Homeosis
Document Summary
Pair rule genes: predict segment locations, which induce. Segment polarity genes: begin segmentation and de ne subregions. Homeotic genes: de ne the role of each segment. Development = di erentiation from egg to mature individual. Step 2 - fertilization: egg is covered with sperm one sperm enters egg membrane sperm nucleus + centriole (forms a part of spindle bers for meiosis) enters the egg envelope around egg expands, clearing away the excess sperm. Step 3 - cleavage cleavage = set of rapid cell divisions after fertilization blastomeres = cells created by cleavage morula = solid mass of cells created by cleavage (solid mass of blastomeres) bastula = morula after further cell division. Step 5: organogenesis gastrula becomes a fetus in 1st trimester. Maternal e ects: cytoplasmic determinant: molecules found in the egg that helps direct early development results in maternal e ects many of these involve segmentation genes.
