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animal development
biol 1210 18.2 & 19
| Question | Answer |
|---|---|
| describe development events during embryonic development | from fertilized egg the zygote goes thru cleavage (2 cell to 32 cell) -> blastula ("ring" of cells around edge of zygote) -> gastrulation (inward folding of the blastula to form blastocel) -> organogenesis & development of tail-bud embryo |
| list steps 1-8 of egg fertilization | sperm contacts egg's jelly coat -> acrosomal reaction -> depolarization of egg membrane -> fusion of egg & sperm membranes -> increase in cytosolic Ca2+ levels -> cortical reaction -> egg activation -> entry of sperm nucleus & fusion w egg nucleus |
| describe the acrosomal reaction of fertilization | the burst of the acrosome in the sperm & release of hydrolytic enzymes & binding btwn sperm proteins & sperm-binding receptors on egg, letting sperm "eat through" jelly coat of egg |
| describe the cortical reaction of fertilization | in the egg, enzymes are released from cortical granules which clip off the egg receptors and lift & harden the vitelline layer (under jelly coat), forming fertilization envelope |
| define polyspermy & describe the prevention of polyspermy | fertilization by more than one sperm, can be mainly achieved by: changing electrical potential of egg membrane (making it more neg. on the outside and blocking polar sperm head) or modification in zona pellucida of egg (outside layers) |
| which steps of fertilization prevent polyspermy? | the depolarization of the egg membrane (fast block) and the cortical reaction (slow block) |
| describe calcium & egg activation during fertilization | the release of Ca2+ (from E.R) in the seconds after sperm nucleus enters spreads & activates the egg = increasing the rate of cellular respiration & protein synthesis in the egg |
| describe cleavage | 1st major phase of embryonic development; rapid series of cell divisions; unicellular zygote -> 2-32 cells -> multicellular embryo. Size remains same, cells get smaller, results in fluid-filled embryo (blastula) |
| structure of blastula | blastomere ("ring" of cells) and blastocel (hollow, fluid-filled space within the blastomere) |
| describe holoblastic cleavage in amphibians | unequal cell division due to dense yolk at the bottom (vegetal pole) slowing down cleavage furrow, resulting in an animal pole (top, small, rapidly dividing cells) & vegetal pole (bottom, slowly dividing cells) |
| describe meroblastic cleavage in birds | macrolecithal, yolk so massive that cleavage furrow can't cut thru it; only small part of egg undergoes cleavage. Yolk doesn't become part of embryo body, but is external food source during development. |
| describe displaced blastocel & grey crescent | in meroblastic cleavage, blastocel pushed toward animal pole bc vegetal pole packed w yolk. Grey crescent: critical landmark visible after fertilization that determines future dorsal-ventral axis of animal |
| describe gastrulation in sea urchin | mesenchyme cells migrate to blastocel -> vegetal plate invaginates -> archenteron forms, mesenchyme cells grow projections towards blastocel -> archenteron grows across blastocel dragged by projections -> mouth/anus forms, 3 germ layers present |
| describe the 3 embryonic germ layers & give example for each | ectoderm: outer layer - epidermis of skin & derivatives, nervous system, ex. cornea. Mesoderm: mid layer - skeletal system, muscular system, ex. circulatory. Endoderm: epithelial lining of digestive tract & respiratory system, ex. stomach lining. |
| what is organogenesis? | the formation of the notochord & neural plate in vertebrate embryonic development |
| describe neural plate formation | begins when underlying notochord sends chemical signals to ectoderm above; flat ectoderm thickens to form neutral plate; edges of plate rise, forming neural folds |
| describe neural groove formation | as edges continue to lift, center of neural plate sinks inward -> forms deep center (neural groove). Microtubules & microfilaments within cells contract to bend tissue. Ensure nervous system is perfectly centred along animal's midline |
| describe neural crest identification | fusion of two "peaks" of folds move towards each other until touching; cells at tip of folds are neural crest cells break away from main tissue. Neural crest cells unique to vertebrates & travel to form face, teeth, nerves, etc. |
| describe internalization (completed tube) of embryonic development | structure "pinches off" to create 2 distinct layers. Neural tube: hollow cylinder is tucked safely inside body, precursor to brain & spinal cord. Outer ectoderm: remaining surface fuses back together to create epidermis on back |
| describe the roles of cytoskeleton in development | changes in cell shape & form neural tube. Microtubules help lengthen cells of neural plate -> actin microfilaments in dorsal side contract -> hinge forms by cell "wedging" -> neural tube forms by pinching off |
| describe cytoskeleton & cell migration | cells migrate by using cytoskeleton to protrude & retract "feet" in amoeba-like movement. Molecules of extracellular matrix guide cell migration & convergent extension |
| describe processes involved in embryonic development of multicellular organisms | cell division - cells multiply. Cell differentiation - cells become specialized in structure & function. Morphogenesis - the organism takes adult shape |
| describe 2 sources of developmental information in the early embryo | cytoplasmatic determinants in the egg: can determine what kind of cell the zygote becomes. Fusion of gametes -> dif. cytoplasmatic determinants split differently in embryo. Induction by neighbouring cells: signals passed btwn cells give info. |
| describe determination & differentiation in muscle cells | from embryonic precursor cell -> certain genes are turned on/off -> myoblast results, "on" gene codes for MyoD, activates myosin -> becomes part of a muscle fiber |
| define determination | cells narrow down their development potential and commit to a specific fate (structure & function) |
| describe different types of cloning | gene cloning: inserting a gene from one species into another. Cell cloning: division of asexually reproducing organisms into identical daughter cells. Organismal cloning: production of a multicellular organism from a single cell. |
| describe cloning plants | adult plants have cells that can de-differentiate & become totipotent (can give rise to all plant types). From their meristems! |
| describe stem cells | undifferentiated cells that can differentiate into many or several cell types. Most differentiated animal cells cannot divide anymore due to cell cycle-blocking genes. From totipotent stem cell -> plurlpotent embryonic stem cells -> multipotent stem cells |
| describe 3 types of animal stem cells & stem cells during development | embryonic stem (ES) cells, adult stem cells & induced pluripotent stem (iPS) cells. In early embryonic dev. animals have toti or pluripotent stem cells. Adults only have stem cells that can produce some specific cell types, ex. bone marrow -> blood cells |
| describe nuclear transplantation | a method of cloning animals. Egg cell donor nucleus + mammary cell donor -> nucleus from mammary cell grown in culture -> early embryo implanted in uterus of 3rd animal -> embryonic development for genetically identical offspring to mammary cell donor |
Created by:
AntBanana
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