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Developmental Bio/Ex
Exam1
| Question | Answer |
|---|---|
| The tansition between spermatogonia and spermatocytes is mediated by ___ secreted by ___ cells. | 1.glial cell line-derived neurotrophic factor (GDNF) 2. sertoli |
| ___levels of GDNF commitment to spermatocyte fate | Low |
| If there is no recombination how many genetically distinct gametes can one pimary spermatocyte generate? | TWO |
| If recombination does occur, how many genetically distinct gametes can one primary spermatocyte generate? | FOUR |
| If a species has 4 pairs of chromosomes and there is no recombination occuring, how many can the male generate? | 2^4=16 |
| What is the DNA content of the primary oocyte? | 4C |
| In xenopus oocyte, the first meiotic arrest happens in what stage of meiosis I? | Prophase |
| During the first meiotic arrest of xenopus oocyte, ___ is active and ___ is inactive. | Myt1(kinase) cdc25 (phosphatase) |
| In xenopus oocyte, to end the first meiotic arrest, the primary oocyte is exposed to ___. | Progesterone |
| Exposure to progesterone causes the xenopus oocyte to polyadenylate ___ mRNA, resulting in its translation | C-mos (phosphatase) |
| C-mos activates a phosphorylation cascade, ultimately leading to the dephosphorylation of the amino acids... | Thr14 and Tyr15 thus activating MPF |
| The second oocyte meiotic arrest is at ___ --> ___ | metaphase --> anaphase |
| The 2nd oocyte meiotic arrest occurs b/c the secondary oocyte synthesizes ____ | cytostatic factor (CSF) |
| what is the role of cytostatic factor (CSF)? | blocks cyclin B degradation and therefore keeps the MPF active. Also inhibits APC^cdc20 |
| In vertebrates, the oocyte is in second meiotic arrest when it is released from the ovary (ovulation) and does not complete meiosis II unless ___ | fertilized |
| The second meiotic arrest ends when ___ is degraded, thereby inactivating MPF. | cyclin B |
| what is the flies version of blood? | hemolymph |
| What is the flies version of the liver? | fat body |
| During maturation, the primary oocyte of vertebrates experiences ___ levels of transcription | high |
| The oocytes of ___ ovaries are not transcriptionally active, instead any molecular synthesis is done by the nurse cells. | meroistic |
| In Drosophila meroistic oogenesis, each oogonium divides ___ times to produce a clone of ___ cells connected to one another by 'ring canals'. The connected cells are called ____ | 4 16 cystocytes |
| 2 of the 16 cystocytes of meroistic oogenesis have ___ ring canal connections and are capable of becoming oocytes and both of them initiate ___ but only of them them completes it | 4 meiosis |
| Germ cells are specified by ___ contained in ____ | specific determinants germ plasm |
| In Drosophila, 'pole cells' i.e. ____ become clustered at the posterior end of the embryo. At the posterior end you will find the pole plasm | primordial germ cells |
| In C. elegans, the P-granules are located ___. After fertilization, the P-granules become segregated to the ___ side of the embryo. | randomly posterior |
| Mature sperm cells are called | Spermatozoa |
| Spermatids are technically haploid but because they are connected to one another through their ____, spermatids function as ___ due to the diffusion of gene products | cytoplasmic bridges diploid cells |
| diploid stem cells that are precursors to sperm: | spermatogonium |
| In humans, spermatogonia do not geneate spermatocytes until ___ | puberty |
| In vertebrates, the common duct of the seminiferous tubule is made of ___ and ____ | vas efferens vas deferens |
| Small duct that carries semen from the testis to the epididymis | vas efferens |
| The main duct that carries semen from the epididymis to the ejaculator tract | vas deferens |
| Spermatogonia line the ___ wall of the seminiferous tubule where they contact the ___ membrane | outer basement |
| any of the elongated cells in the tubules of the testes to which the spermatids become attached; they provide support, protection and, apparently, nutrition until the spermatids are transformed into mature spermatozoa. | Sertoli cells |
| glial cell line-derived neurotrophic factor (GDNF) is expressed by the ___ | sertoli cells |
| In order to complete meiosis I, primary spermatocyte loses contact with the basement membrane of the seminiferous tubule and crosses the ___ into the inner layer of the tubule wall. | sertoli cell barrier |
| The primary spermatocyte completes meiosis I to form two secondary spermatocytes (__C--> __C) | 4C--> 2C |
| the acrosomal vesicle is formed from teh ____ | golgi apparatus |
| small proteins that are 60% arginine, which tightly package the chromosomes, and eventually cause the complete shutdown of transcription in the spermatids: | protamines |
| ____ shuffles maternal and patenal alleles that are located on different chromosoems, but it cannot shuffle alles that are located on homologous chromosomes | Independent Assortment |
| ____ shuffles maternal and paternal alles located on homologous chromosomes | Genetic Recombination |
| Genetic Recombination produces genetic differences between the ____ | sister chromatids |
| If independent assorment were the only mechanism giving rise to gamete genomes, a single human diploid spermatocyte could give rise to ____ different possible haploid chromosomal compliments | 2^23 |
| When is the first meiotic arrest of oogenesis? | at teh diplotene stage of meiotic prophase I |
| In meiosis I, the oogonium replicates its DNA (4C). As soon as it enters ___ it is designated as primary oocyte (4C) | prophase I |
| During the ____, yolk proteins such as viteloogenin are taken up by the oocyte. | first meiotic arrest |
| During maturation, the primary oocyte of xenopus experiences very high levels of txn. An indicator of this high level of txn during the first meiotic arrest would be the ____ | lampbrush chromosomes (sites of active RNA transcription). The chromosomes are stretched out |
| The transient amplification of the rRNA genes breaks the rule of ____ | genomic equivalence: the genomic content of most cells is constant |
| What ribosome structure is stockpiled during xenopus oogenesis? | 5S RNA (minimally expressed in diploid somatic cells but huge in haploid genome |
| 5S genes contain an internal ___ that binds to a transcription factor called ___ | promoter TFIIIA |
| chorion protein is: | eggshell protein |
| In vertebrate animals, the oocyte is in second meiotic arrest when it is released from the ovary and does not complete meiosis II unless fertilzied. Should fertilization occur, ___ enter the oocyte and activate the protein ___ | Ca2+ ions calmodulin |
| Activating the protein calmodulin leads to 1)___ 2)___ 3)___ 4) ____ | degradation of CSF degradation of cyclin B inactivation of MPF completion of meiosis II |
| In meiotic arrest I, all three amino acids on MPF are phosphorylated so MPF is inactive. The kinase that phosphorylates Thr14 and Tyr15 is? | Myt1 |
| In meiotic arrest I, all three amino acids on MPF are phosphorylated so MPF is inactive. The phosphatase that needs to be activated by the phosphorylation cascade caused by c-mos (triggered by progesterone) is? The kinase deactivated by the cascade is? | Cdc25 myt1 |
| Thrionine161 is ___ phosphorylated | constitutively |
| What are the 3 layers of the ECM surrounding the egg? | 1) vitelline envelope or zona pellucida 2) jelly coat (not present in humans) 3) egg cell membrane (immediately within the egg cell membrane) |
| Lying beneath the membrane of the egg is a thin layer of gel-like cytoplasm called: | cortex |
| within the cortex are the ___ which contain proteolytic enzymes | cortical granules |
| The vitelline envelope is a tough coating of ___ that tightly adheres to the cell membrane of unfertilzied egg. | glycoproteins |
| Soem of the glycoproteins of the vitelline envelope are synthesized by the ___ itself and some are synthesized by the ovarian ___ and secreted onto the surface of the egg | oocyte follicle cells |
| following a gradient of chemicals secreted by the egg is called: | chemotaxis |
| Sperm have receptors in their membrane that binds Resact (in sea urchin). These receptors have ____ activity | guanylyl cyclase. This means that the receptor leads to the formation of cGMP. |
| cGMP helps open ___ channels in the sperm cell membrane | calcium |
| The Ca2+ influx into the sperm cell membrane provides a ___ for the sperm | directional cue |
| Fusion of the sperm and egg membrane is mediated by ___ | bindin, a fusogenic protein. |
| the acrosomal process carries a protein called ___ | bindin |
| Recent data has shown that the fusogenic region of binding will not operate (fuse vesicles) on a ___ charged surface | positively (remember fast block to polyspermy) |
| The slow block to polyspermy is caused by the ____ | cortical granule reaction |
| The space between the vitelline envelope and the egg membrane: | perivitelline space |
| The released contents of the cortical granules alter teh vitelline envelope in order to reduce polyspermy. What are its contents? | proteolytic enzymes, glycosaminoglycans, peroxidase enzymes and transglutaminase, hyalin (doesn't affect polyspermy) |
| What do proteolytic enzymes do? | digest the proteins that once anchored the vitelline envelope to teh egg cell membrane and clip off bindin receptors |
| What do glycosaminoglycans do? | They are sulfated polysaccharides that increase the osmotic pressure in the perivitelline space |
| What does peroxidase enzyme do? | harden teh fertilization envelope by crosslinking tyrosines residues on adjacent proteins. |
| The blastomeres of a cleavage-stage embryo rely entirely on ____ gene products. | maternal |
| Cleavage divisions cease shortly before the time of ____ | gastrulation |
| A frog embryo undergoes 12 rounds of ___ cleavage division | synchronous |
| The 13th round of cell division in frogs heralds the ___ | mid-blastula transition (MBT) |
| Following the MBT, the cells of the embryo introduce G phases. The length of these G phases varies from cell to cell, with the result that post-MBT cell divisions are ___ | asynchronous |
| Following MBT, blastomeres acquire the capacity to become ___ | motile |
| Cell division synchrony is lost at MBT because different cells express zygotic mRNAs that are translated into different ___ of MPF. | regulators |
| What are mitotic domains? | Groups of cells undergoing mitosis at the same time |
| In drosophila, cycles 1-10 are short in length with almost synchronous nuclear division. Cycle 13 is the last cycle in the ___ stages | syncytial |
| In drosophila, cycle 14 is when the embryo ___ cellularizes | asynchronously |
| In drosophila, the asymmetric cycle 14 division are under control of the phosphatase ____ | String (a tyrosine phosphatase). It's important to note that ultimately, a complex of CDC2/cyclin also controls the G2/M transition |
| In most animals, cleavage is accompanied by the formation of a ___ | blastocoel (a liquid-filled space) |
| What are the two main functions of the blastocoel? | 1) provides a space for cell migration during gastrulation 2) prevents the cells beneath it from interacting prematurely with the cells above it |
| What prevents diffusion between the blastocoel and the world outside? | the polarized blastomeres express tight junctions where they contact one another along their apical perimeters. |
| What lines the wall of the blastocoel and what creates this lining? | the basement membrane (also called 'basal lamina') is a meshwork of secreted proteins (like the ECM) that is syntehsized and secreted by the polarized blastomeres |
| In Xenopus, the integrity of the blastocoel is maintained by the expression of ___ | EP-cadherin |
| How does yolk influence cleavage? | Since yolk is dense, it influences the ability of cleavage furrows to form between dividing blsatomeres. |
| The animal pole is defined by the ___ and is the site of ____ extrusion | oocyte nucleus polar body |
| Cells tend to flatten out (maximize contact area) on ____ neighbors | strongly adhesive |
| Cells tend to ___ (minimize contact area) where they touch poorly adhesive neighbors | round up |
| Glycosaminoglycans (GAGs) are also known as ___ and are long unbranched polysaccharides. | mucopolysaccharides |
| What molecule sticks to GAGs? | water |
| GAG chains may be covalently linked to a protein to form ____ | proteoglycans |
| During gastrulation, cells on the outside of the blastula move into the ___. This process produces a multilayered embryo or gastrula. | blastocoel |
| Ectoderm is created by the ___ | mesomeres (top cells) |
| Endoderm is created by the ___ | macromeres |
| mesoderm is created by the ____ | micromeres |
| The 4 stages of gastrulation are: | 1) ingression of primary mesenchyme 2) invagination of archenteron 3) elongation of archenteron 4) fusion of roof of archenteron & ectoderm |
| An endodermal cell population derived from the macromeres that were produced at the 4th round of cleavage: | Vegetal Plate |
| Invagination is caused by ____ | shape changes |
| The hyaline layer has two distinct layers: | inner and outer lamina |
| The vegetal plate cells secrete ____ into the inner lamina of the hyaline. | chondroitin sulfate proteoglycan |
| The chrondroitin sulfate in the inner lamina absorbs water and swells, pushing against the ___ and inward on the ___ to which it is attached. This causes the archenteron to push into the blastocoel. | outer lamina epithelium |
| Even though the mesenchyme and vegetal plate enter the blastocoel, the spherical embryo retains its original diameter and external surface area. How? | |
| no chromosome diminution = ? | germline |
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ArtofScience
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