Biology Study Guide Test #1:How is development controlled?Cell division & cell differentiation Zygote Single cell/fertilized eggTranscription Synthesis of RNA from DNAmRNA Carries genetic message from DNA to the protein-synthesizing machinery of the cellTranslation Synthesis of polypeptide using the information in the mRNARNA to Protein Ribosomes Site of translationTranscription/translation in prokaryotes vs. eukaryotesTranscription and translation in prokaryotes are both in the cell (no processing of the mRNA) while in eukaryotes transcription and rna processing are in the nucleus while translation are outside the cell RNA polymerase Pries DNA open and copies DNA in the 5’ to 3’ directionPromoter DNA sequence where RNA polymerase attaches and initiates transcription (in prokaryotes it binds directly)Transcription factors In eukaryotes a collection of proteins that mediate the binding ofrna polymerase and the initiation of transcriptionCodons A triplet code for amino acidsOperator Switch that turns genes on/offPositioned within the promoter; controls the access of rna polymerase to the genes Operon Operator, the promoter and the genes they control = the operonTerminator In prokaryotes, the sequence that terminates transcriptionTranscription initiation complexThe whole complex of transcription factors and RNA poly. bound to the promoterTATA box Sequence that forms the initiation of transcription in eukaryotes Trp operon Usually turned onRNA poly. can bind to the promoter and transcribe the genes of the operonCan be turned off by trp repressorRepressor Binds to operator and blocks attachment of rna poly. to the promoter therefore preventing transcriptionRegulatory gene Expressed continuously at a low rateTrp repressor Inactive form with little affinity for operator; if tryptophan binds to trp repressor at allosteric site it can change it to active form and turn off operon Corepressor Cooperates with repressor to turn off operonEx tryptophan Repressible operon (trp) because it is on but can be repressed/turned off when tryptophan binds to repressor to turn off operonInducible operon Operon is off but can be stimulated/induced when a molecule interacts with a regulatory protein(lac operon)Lac operon Lac repressor is active on its own so gene transcription is usually offInducer Inactivated repressor to turn on transcriptionNegative gene regulation Lac/trp are examples Positive gene regulation When glucose and lactose are present, e. coli usually uses glucoseWhen lactose is present and glucose is low, e coli will use lactose Cyclic amp (cAMP) accumulates when glucose is scarce The regulatory protein called CAP (an activator) activates transcription by binding to DNA When camp binds to CAP, cap assumes its active shape and can facilitate the binding of rna poly. to the promoter and therefore directly stimulates transcription Histone acetlyation When acetyl groups are attached to lysines in histone tails (in chromosomes)When lysines are acetylated the positive charges are neutralized and therefore cannot bind –when chromatin binding doesn’t occur, the chromatin has a looser structureLoose structure = transcription proteins having an easier access to genes Fertilization Formation of a diploid zygote from a haploid egg and sperm Process of fertilization: Sperm penetrate/dissolves protective egg layer to reach plasma membrane Molecules on the sperm bind to receptors on egg surface to ensure that a sperm of same species fertilizes the eggAcromosomal reaction Fusion of sperm and egg, triggering depolarization (Na+ ions)Increase in Ca2+ concentrationCortical reaction Acromosomal reaction Begins with discharge of hydrolytic enzymes from the acromosomeThese enzymes help digest the jelly coatDepolarization: Fast block to polyspermyCortical reaction Slow block to polyspermy Granules in egg fuse with plasma membrane and from fertilization envelope Polyspermy Entry of multiple sperm nuclei into the eggActivation of egg results from?Ca2+ high concentrationCleavage After fertilizationRapid cell division that creates smaller cells called blastomeresBlastula 5-7 divisions that creates a hollow ball of cells Blastoceol A fluid filled cavity that is surrounded by the blastulaYolk Usually in vegetal pole and store of nutrientsHoloblastic Cleavage furrow goes through entirely throughMeroblastic Incomplete cleavage of yolk rich egg (birds)Vegetal pole Where egg yolk concentration is highestAnimal pole Lower concentration of egg yolkMorphogenesis Cellular and tissue based process where animal body takes shapethere are two stages- gastrulation Cells at/near surface of blastula move to interior, cell layers established, primitive digestive tube formed- organogenesis Formation of organs -gastrulation- Reorganization of hollow blastula into a 2-3 layered embryoThese layers are the cell layers/germ layersEctoderm Outer layerEpidermisNervous systemEndoderm Lines digestive tractMesoderm Between ectoderm and endoderm; skeletal/muscular systems, circulatory and reproductiveEnd of cleavage in humans Creates a blastocystOne side of the blastocyst has a cavity called the inner cell massTrophoblast Outer part of blastocyst Initiates implantation but doesn’t contribute to embryo,Gastrulation is sea urchins: Begins at vegetal pole of the blastulaInvagination begins where sheet cells begin to fold over and buckle inwardExtensive rearrangement of cells transforms the shallow depression into a deeper, narrow tube called the archenteronThen after the open end of the archenteron becomes the blastopore, a second opening dfor the mouth forms on the opposite end of the archenteron when the archenteron touches the inside of t he ectoderm and the two layers fuse creating the digestive tubeBlastopore The open end of the archenteron which will become the anusGastrulation in frogs The blastula for frogs is a large yolk-laden cell in the vegetal hemisphereFrogs are bilaterally symmetrical animals so they have a dorsal (front) side, ventral side (bottom), left and right side, and then anterior (front) and posterior (back) side-Gastrulation begins when a small indented crease (the blastopore) appears on the dorsal side of the late blastula. thecrease is formed by the cells invaginating. The outer cell sheets then roll inward on the dorsal lip (which is the part above the crease) and then move to the interior which then forms the endoderm and mesoderm. At the animal pole, cells change shape and begin to spread over the
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