Development Lecture 2 Chapter 12 04 21 2015 Know that cells grow synthesize DNA and divide in a cycle with distinct phases Interphase G1 the first part of interphase S phase chromosomes duplicate G2 last part of interphase Mitotic phase mitosis distributes daughter nuclei and cytokinesis divides cytoplasm producing two daughter cells Mitosis Prophase chromatin fibers become more tightly coiled mitotic spindle begins to form each chromosome appears as two identical sister chromatids joined at their centromeres Prometaphase nuclear envelope fragments each of the two chromatids of each chromosome now has a kinetochore a specialized structure at the centromere Metaphase The centrosomes are now at opposite poles of the cell Anaphase shortest stage of mitosis sister chromatids of each pair to part suddenly Each becomes a full fledged chromosome two daughter chromosomes begin moving toward opposite ends of cell as microtubules shorten Telophase two daughter nuclei form in the cell nuclei envelopes arise from the fragments of the parent cell s nuclear envelope and other portions of the endomembrane system Mitosis is now complete Understand that the cell cycle is controlled by molecules present in the cytoplasm that regulate movement of the cycle past checkpoints Lecture 3 Chapter 35 2 Understand that meristems are sites of cell division and that development occurs after cell division Meristems perpetually dividing unspecialized tissues o Divide when conditions permit o Lead to new cells that elongate and become specialized Apical meristems located at the tips of roots and shoots additional cells that enable growth in length Lateral meristems growth in thickness Lecture 4 Chapter 18 Control of transcription occurs through the binding of activators or repressors to special sites on the DNA Activator protein that binds to DNA and stimulates transcription of a gene Repressors inhibits transcription Know that gene expression in eukaryotes can be controlled at multiple stages during transcription and translation DNA methylation condensation of chromatin and reduce transcription Histone acetylation promote transcription by opening up the chromatin structure Epigenetic inheritance inheritance of traits transmitted by mechanisms not involving the nucleotide sequence itself Know that modification of histone structure can affect transcription Chemical modifications to histones the proteins around which DNA is wrapped in nucleosomes play a direct role in the regulation of gene transcription o The N terminus of each histone molecule in a nucleosome protrudes outward from the nucleosome These tails are accessible to various modification enzymes that catalyze the addition of removal of specific chemical group such as acetyl methyl and phosphate Know that enhancers and transcription factors can affect transcription Transcription factors proteins involved in transcribing DNA into RNA Includes RNA polymerase that initiate transcription of genes Lecture 5 Chapter 18 Cell differentiation occurs during early development because of different concentrations of cytoplasmic determinants Cytoplasmic determinants in the unfertilized egg regulate the expression of genes in the zygote and embryo that affect the developmental fate of the embryonic cells The unfertilized egg the cytoplasmic determinant are unevenly distributed after fertilization and mitotic cell division the cell nuclei of the embryo are exposed to different sets of cytoplasmic determinants and as a results express different genes Lecture 6 Chapter 47 Understand that polyspermy is blocked by 2 mechanisms in sea urchins and why blocking multiple fertilizations is important Know that cleavage has different patterns in different organisms and what those patterns are look at picture on pg 1042 Holoblastic frogs cleavage is asymmetric reflecting the asymmetric distribution of yolk across the egg Yolk is often concentrated toward one pole called the vegetable pole and away from the opposite pole called the animal pole o When the animal cell divides cleavage furrow forms eventually four blastomeres form the animal pole to the vegetal pole o During the third division the yolk begins to affect the relative size of cells produced in the two hemispheres o Yolk near veggie pole displaces mitotic apparatus toward animal pole This in turn displaces cleavage furrow from the egg equator toward animal pole yielding smaller blastomeres in the animal hemisphere than in the veggie hemisphere Meroblastic bird eggs yolk is most pronounced and has its most pronounced effect on cleavage in the eggs of birds other reptiles many fishes and insects o Incomplete cleavage of yolk rich eggs o Yolk is actually entire egg cell divisions limited to small whitish area at he animal pole Lecture 7 Chapter 47 Know that gastrulation produces three basic types of embryonic cells 1 Mesenchyme cells migrate from the vegetal pole of the blastula into the blastocoel 2 Invagination cells at the vegetal pole flatten slightly causing vegetal pole to buckle inward 3 Endoderm cells form archenteron the future digestive tube New mesenchyme cells at the tip of the archenteron send out thin extensions filopodia toward the blastocoel wall 4 The extensions contract dragging the archenteron across the blastocoel The open end of the archenteron which will become the anus is called the blastopore Fusion of the archenteron with the blastocoel wall forms the digestive tube which now has a mouth and an anus Understand that the archenteron is the embryonic gut forms as a result of gastrulation Lecture 8 Chapter 47 Understand that the position of regions of the embryo relative to one another provides information that determines the formation of organs 3 body axes are established relative to poles of zygote and frst cleavage vegetable pole becomes posterior Know the examples from neurulation notochord stimulates the formation of the neural plate neural tube stimulates neural crest cells 1 Neurulaton of surface ectoderm cells is induced by underlying NOTOCORD a skeletal rod in chordates formed from DORSAL MESODERM 2 NEURAL PLATE forms thickening of ectroderm caused by changes in cell shape 3 NEURAL FOLDS and NEURAL GROOVE form 4 NEURAL TUBE forms once neural folds meet eventually becomes SPINAL CORD AND BRAIN 5 Paired SOMITES of meso Tissue flank neural tube somites paired blocks of mesodermal cells extending serially along neural tube Lecture 9 Understand that hormones act over the entire body Hormone a
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