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Description
Flashcards by Candice Young, updated more than 1 year ago
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Created by Candice Young
over 8 years ago
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| Question | Answer |
| End result of spermatogenesis | four non-identical sperm cells produced |
| End result of oogenesis | 1 large ovum produced and 3 non-functional polar bodies |
| Fertilization | oocyte undergoes meiosis, sperm cell fuses with ovum to form a zygote |
| Cleavage | lots of RAPID cell divisions in zygote, very little growth or transcription, reduction of cytoplasmic volume, axes form |
| Blastula | hollow ball of cells resulting from cleavage |
| Gastrulation | make 3 distinct "germ" layers (endoderm, mesoderm, ectoderm) in Blastula, results in primitive gut formation |
| Gastrula | 3 layered embryo |
| ectoderm | forms nervous system and outer layers of skin |
| endoderm | forms digestive tract. respiratory tract, and digestive organs |
| mesoderm | forms kidneys, heart, muscles, bones |
| Animal pole vs vegetal pole | Animal pole divides faster; dark brown coloring in Xenopus laevis; later are the ectoderm axis |
| Cell movements during gastrulation | a lo of cells rush in from the outside and the rest spread themselves out (epiboly) thinly in an stretched out layer |
| Molecular basis of gastrulation | changes in cell adhesion |
| fate maps | tracking cells in time and space; show where each tissues of germ layer originally came from; do NOT inform us about when states of cell determination occur |
| Roux's experiment | experimented by killing one frog blastomere cell at two cell-stage and observing the other's development concluded that blastomeres at the earliest stage have a predetermined fate and only a half embryo can form |
| Driesch's experiment | separated sea urchin cells at two-cell stage and observed growth of a small but otherwise normal larvae revealed that at two (and four) cell stages, individual blastomeres are totipotent |
| totipotency | the capacity for a cell to give rise to any embryonic cell type |
| Horstadius' tier experiments | separate cells at 8 cell stage --> get a ciliated blastula and a vegetalized blob reveals how cells lose totipotency and become committed to a developmental fate as development proceeds |
| John Gurdon's experiments | take adult frog skin cell and tadpole gut epithelial cell, destroy nuclei, and transfer nucleus into unfertilized eggs --> tadpoles develop shows that genetic information is not lost as cells differentiate |
| Regulative Development Model | early embryos have a capacity for regulation; have developmental plasticity |
| Asymmetric Division | Sister cells can be born differently despite having the same genetic information |
| Symmetric Division | Sister cells with the same genetic information become different as a result of different neighbors acting on them |
| How do cells know which genes to express? | the combination of internal information from asymmetrical distribution & external information from cell-cell signaling |
| How animal-vegetal axis is determined (in Xenopus) | Determined maternally; egg radially symmetric before fertilization & there is differential localization of maternal mRNAs |
| How dorsal ventral axis is determined (in Xenopus) | determined by where the sperm enters --> makes the cortex rotate 30 degrees |
| Induction | cell-cell interactions cause special tissues to develop |
| Spemann's separation experiment | divided two cells with a baby hair, one half could grow own embryo BUT plane of division is crucial |
| The Organizer | cluster of cells in developing amphibian embryo that induce development of central nervous system; crucial discovery to concept of induction |
| dorsal lip of the blastopore | cells that are COMMITTED to invaginate into the blastula, "the Spemann organizer," formed by the gray crescent region of an egg |
| Results of dorsal lip transplant | continued to be committed to its "fate" --> initiated a second gastrulation in surrounding tissue and two embryos/axes form via induction |
| B-catenin | protein that can induce changes in cell fates based on where it accumulates; can form new dorsal regions when injected |
| Specification | when the mesoderm is under the ectoderm, tissue is specified to become the nervous system BUT if moved it could become something else NOT irreversible! |
| Determination | when cells will produce the determined cell types and will not be altered by inducers to become completely different IRREVERSIBLE |
| Involuting Marginal Zone cells | on the dorsal lip of the blastopore in developing Xenopus eggs, move to the interior via invagination and become the mesoderm |
| Neurula | What the embryo is called after gastrulation leads to the formation of the neural fold --> notochord |
| What's in a human sperm cell? | Haploid nucleus, centriole (forms spindles during division), mitochondria, acrosome enzymes (to digest egg coat) |
| What's in a human egg cell? | Egg cytoplasm: nutritive proteins, ribosomes & tRNA, **mRNAs**, morphogenetic factors, protective chemicals, egg cortex (cortical granules) Vitelline membrane to attract and activate sperm + regulate ion flow |
| Egg-sperm recognition | Exocytosis of sperm's acrosomal vesicle, bindin coats sperm actin filaments and binds sperm to vitelline envelope, sperm passes through and membranes fuse |
| Fast block to polyspermy | Depolarization of egg electric potential due to influx of Na+ means no more sperm can fuse |
| Slow block to polyspermy | cortical granules cleave links between vitelline membrane and plasma membrane, stimulated by increase in intracellular Ca2+ from sperm fusion |
| Follicle Stimulating Hormone (FSH) | produced by pituitary gland, controls production of oocytes in women and sperm in men; stimulates production of estrogen in women |
| Corpus luteum | involved in production of progesterone, left behind after egg leaves in ovulation, maintains uterine lining (endometrium) |
| Luteinizing hormone | hormone that triggers ovulation and development of corpus luteum |
| where does fertilization (as well as the first cleavage) occur? | in the fallopian tube/OVIDUCT |
| first ball of cells after cleavage in humans | the morula |
| human chorionic gonadotrophin (hCG) | hormone secreted by specialized cells that maintains the corpus luteum after implantation |
| Implantation | human blastula is implanted into endometrium, trophoblast outer layer forms placenta so direct nutrient exchange can occur |
| chorionic gonadotropin | hormone secreted by trophoblast and chorion that maintains corpus luteum after implantation |
| The Four Extra-embryonic Membranes | 1) Chorion 2) Amnion 3) Yolk Sac 4) Allantois |
| Chorion | trophoblast, surrounds everything |
| Amnion | cushions embryo and prevents desiccation; is fluid filled |
| Yolk sac | forms blood cells that migrate into the embryo, doesn't actually contain yolk |
| Allantois | develops from archenteron (gut) outgrowth, becomes a part of the umbilical cord |
| First Trimester | three germ layers --> limb buds --> developed enough to be called an embryo (non-self) --> limb elongation --> organs are in place --> hCG levels drop and CL begins to disentegrate |
| Second Trimester | progesterone production --> general growth --> bone development --> heart beating --> vernix (skin) covering |
| Third trimester | weight increase --> eyelids split --> lungs mature --> hearing develops --> uterine cavity full |
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