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DEVELOPMENTAL BIOLOGY
REVIEWED PRACTICE EXAM
Embryogenesis - CORRECT ANSWER-the stages between fertilization and birth (hatching) Stages of embryogenesis - CORRECT ANSWER-Fertilization - Fusion of gametes Cleavage- extremely rapid mitotic divisions immediately following fertilization (formation of blastula) Gastrulation - Blastomeres (cells of blastula) undergo dramatic movements and change their position relative to one another; formation of 3 germ layers (endoderm, ectoderm, and mesoderm) Organogenesis - production of tissues and organs Metamorphosis - Transition from larvae (sexually immature) to adult (sexually mature) Gametogenesis - Formation of gametes Fertilization - CORRECT ANSWER-Fusion of gametes Cleavage - CORRECT ANSWER-extremely rapid mitotic divisions immediately following fertilization (formation of blastula) Gastrulation - CORRECT ANSWER-Blastomeres (cells of blastula) undergo dramatic movements and change their position relative to one another; formation of 3 germ layers (endoderm, ectoderm, and mesoderm) Organogenesis - CORRECT ANSWER-production of tissues and organs
Metamorphosis - CORRECT ANSWER-Transition from larvae (sexually immature) to adult (sexually mature) Gametogenesis - CORRECT ANSWER-Formation of gametes Where does gastrulation occur - CORRECT ANSWER-at a point on the embryonic surface roughly 180 degrees opposite the point of sperm entry w/ formation of a simple called the blastopore what development does the blastopore mark? - CORRECT ANSWER-the future dorsal side of the embryo and becomes a ring Cells that migrate through the blastopore to the embryo's interior become mesoderm and endoderm what do ectoderm cells develop into - CORRECT ANSWER- epidermis, brain and nerves what do endoderm cells develop into - CORRECT ANSWER- Lining of the gut and respiratory systems what do mesoderm cells develop into - CORRECT ANSWER- Connective tissue, muscle, blood, heart, skeleton, gonads and kidney what does Organogenesis begin - CORRECT ANSWER-when cells on the most dorsal region of the mesoderm condense to form a rod of cells called the notochord Notochord - CORRECT ANSWER-A rod of mesoderm that separates the embryo into right and left halves and instructs the ectoderm above it to become the nervous system The mesodermal tissue adjacent to the neural tube and notochord become...? - CORRECT ANSWER-somites (the precursors to back muscles, spinal vertebrae, and dermis)
- Cell growth
- Cell death
- Changes in the composition of the cell membrane or secreted products Neural crest - CORRECT ANSWER-A transient band of cells that joins the neural tube to the epidermis Methods for keeping track of cells (4) - CORRECT ANSWER-1. Direct observation
- Dye marking
- Genetic labeling - Creating chimeric embryos (embryos made from tissues of more than one genetic source)
- Transgenic DNA chimeras - Inserting GFP or another similar gene Differentiation - CORRECT ANSWER-Process during the cell stops dividing and develops specialized structural elements and takes on a distinct form 2 stages of Commitment - CORRECT ANSWER-1. Specification: Cell commitment is still capable of being altered
- Determination: When cell is capable of differentiating autonomously even when placed in another region of embryo or environment (commitment is irreversible) Autonomous Specification - CORRECT ANSWER-Blastomeres of the early embryo are apportioned a set of determination factors w/in the egg cytoplasm aka different regions of egg have different morphogenetic determinants (basically transcription factors that regulate to path of development) Who provided evidence of Autonomous Specification - CORRECT ANSWER-1905 Embryologist Edward Conklin provided evidence of autonomous specification by fate mapping tunicate Styela partita (sea squirt)
Conditional Specification - CORRECT ANSWER-What Cell becomes is specified by interactions with neighboring cells ex:
- cell to cell contact (juxtacrine factors),
- secreted signals (paracrine factors)
- physical properties of its local environment (mechanical stress) Who provided evidence of Conditional Specification - CORRECT ANSWER-Conditional Specification proven by August Weismann in 1888 with his germ plasm theory. (He attempted to disprove conditional specification but ended up providing evidence for it) Describe conditional specification in Sea urchin embryo experiment - CORRECT ANSWER-Hans Dreisch: Intact 4-cell sea urchin embryo yields normal pluteus larva
- **When each of the four cells is isolated, they each yield smaller but normal pluteus larva (see pg 36 fig. 2.9)
- He also demonstrated conditional specification in Sea Urchin by Pressure plate experiment (reshuffling of nuclei in between dorsal and ventral regions using glass plate) Solenoids - CORRECT ANSWER-structures that inhibit transcription in somatic cells
- Prevent transcription factors (TFs) & RNA polym. from accessing genes Histone acetylation - CORRECT ANSWER-addition of (-) charged acetyl groups to neutralize & loosen histones Histone acetyl transferases → put acetyl groups on → activates txn Histone deacetylases → take acetyl groups off → prevents txn Histone methylation - CORRECT ANSWER-usually heterochromatic (tightly packed) & represses txn
Poly-A tail added Introns removed, exons spliced together mRNA ready to be translated outside of nucleus Cis-regulatory elements: - CORRECT ANSWER-promoters, enhancers, silencers located on same chromosome as gene Promoters: - CORRECT ANSWER-regions where RNA Polym II binds to gene to initiate txn CpG islands: - CORRECT ANSWER-regions rich in sequence of CG Basal Transcription Factors: - CORRECT ANSWER-bind to CpG islands & recruit RNA Polym II to position in for txn Enhancers: - CORRECT ANSWER-signal where/when promoter can be used & how much gene product to make Silencers: - CORRECT ANSWER-prevent promoter use; inhibit gene txn Neural restrictive silencer element (NRSE): - CORRECT ANSWER-prevents promoter's activation in any tissue except neurons Transcription Factors: - CORRECT ANSWER-proteins that can recruit other proteins to unwind DNA & form bridges to bring enhancer close to promoter Mediator: - CORRECT ANSWER-bridge b/w enhancer & promoter, connects RNA Polym II to enhancer Pre-initiation complex: - CORRECT ANSWER-structure containing mediator, RNA Polym II, its cofactors
Cohesin: - CORRECT ANSWER-protects chromatin loop created by mediator Transcription Elongation Complex (TEC): - CORRECT ANSWER-Releases RNA Polym II Transcript Elongation Suppressor: - CORRECT ANSWER- prevents TEC from associating w/ RNA Polym II Enhancer modularity: - CORRECT ANSWER-genes have several separate enhancers that can allow protein to be expressed in specific tissues but not in others 3 Transcription Factor Domains: - CORRECT ANSWER-1. DNA-binding Domains → recognize specific DNA sequences in enhancer
- Trans-Activating Domains → activate/suppress txn of gene corresponding to promoter/enhancer it has bound to
- Protein-Protein Interaction Domains → allows TFs to regulate activity of specific TF Insulator: - CORRECT ANSWER-limit the range in which enhancer can activate gene expression Pioneer Transcription Factors: - CORRECT ANSWER-bind to enhancer DNA sequences in repressed chromatin, thereby opening it up enough to allow other TFs to access the promoter Master Regulator: - CORRECT ANSWER-(1) expressed when specification of cell begins (2) regulates expression of genes specific to cell type (3) can re-direct a cell's fate to this cell type Briggs and King, John Gordon - CORRECT ANSWER- Replaced nucleus in frog egg w/ nucleus of terminally differentiated cell → developed into normal frog
(2) Can recruit proteins that help w/ methylation or deacetylation (stabilize nucleosomes → harder for TFs to access DNA) Inheritance of DNA Methylation Patterns - CORRECT ANSWER-DNA methyltransferase-3 methylates unmethylated cytosines → can be transmitted to next generation Genomic Imprinting & DNA Methylation - CORRECT ANSWER-When only the sperm-derived/egg-derived allele of a gene is expressed During spermatogenesis/oogenesis, existing methyl groups are taken off chromatin and replaced w/ sex-specific ones DNA Methylation - CORRECT ANSWER-Silences DNA by (1) interfering w/ binding of gene-activating TFs (2) recruiting proteins that stabilize nucleosomes Stem cell - CORRECT ANSWER-retains the ability to divide and recreate itself while also having the ability to generate progeny capable of specializing into a more differentiated cell type Potency - CORRECT ANSWER-ability a stem cell has at producing many different types of cells Asymmetrical Division - CORRECT ANSWER-Produce 1 self renewing stem cell and 1 committed to differentiate Totipotent - CORRECT ANSWER-Can make all cell types Ex: Body, germ cells, placenta, amnion, and yolk sac (Fertilized egg) Produce embryonic stem cells Embryonic stem cells - CORRECT ANSWER-Can make all cell types of the embryo Ex: Inner cell mass (blastocyst)
Multipotent - CORRECT ANSWER-Make many types of cells with restricted specificity for the tissue where they reside Ex: Adult stem cells Hematopoietic - CORRECT ANSWER-make all blood cells Adult stem cells - CORRECT ANSWER-normally multipotent stem cells possessed by adult organs Progenitor - CORRECT ANSWER-a cell not capable of unlimited self renewal Unipotent stem cell- - CORRECT ANSWER-function in the organism to generate only one cell type, ex; sperm cells Stem cell niche- - CORRECT ANSWER-regulates stem cell renewal, survival and differentiation Inner cell mass- - CORRECT ANSWER-Pluripotent stem cells of the inner cell mass are the most studied stem cells Blastocyst- - CORRECT ANSWER-made up of the spherical layer of trophectoderm surrounding the inner cell mass and the fluid filled cavity called the blastocoel Embryonic germ cells- - CORRECT ANSWER-Isolated embryonic stem cells grown in culture Regenerative medicine- - CORRECT ANSWER-pluripotent stem cells allow ESC's to differentiate into any cell type important for degenerative conditions such as alzheimer's and parkinson's disease Hypomorhic mutations- - CORRECT ANSWER-mutations that reduce gene function
What causes the different cleavage patterns observed? - CORRECT ANSWER-Cleavage patterns are influenced by the amount and distribution of yolk and by cytoplasmic factors When yolk occurs distribution of yolk is not homogenous- settle to one side of eggs, which creates what? - CORRECT ANSWER-1 Yolk abundant side- "vegetal hemisphere" - end of which is called "vegetal pole" 2 yolk depleted side (no or little yolk)- "animal hemisphere"- end of which is called "animal pole" Holoblastic cleavage - CORRECT ANSWER-Complete cleavage.
- low to moderate yolk
- has early feeding larvae Two types: Isolecithal (small yolk distribution) and Mesolecithal (moderate yolk distribution) Holoblastic cleavage patterns - CORRECT ANSWER-"radial- rotational cleavage" 1 Sea cucumber called Synapata- Radical cleavage 2 Urchins- modified radical cleavage 3 Frogs- mesolecithal cleavage (modified radical cleavage) 4 Mammals- rotational cleavage Several hours after fertilization, cleavage results in the formation of a hollow ball of cells called a _____. A.)blastomere B.)morula C.)trophoblast
D.)gastrula E.)blastula - CORRECT ANSWER-E.)blastula What is the function of the blastocoel? - CORRECT ANSWER- Prevents contact between vegetal and animal cells and provides space for gastrulation movements Blastocoel - CORRECT ANSWER-The fluid-filled cavity within the blastula Blastomeres - CORRECT ANSWER-Any of the cells resulting from the cleavage of a fertilized ovum during early embryonic development that together form the blast What are the cells created by cleavage called? A.)Blastopores B.)Blastocoels C.)Blastomeres D.)Blastulas - CORRECT ANSWER-C.)Blastomeres 2 Urchins- modified radical cleavage steps - CORRECT ANSWER-1 Meridional (same) 2 Meridional (same) 3 equatorial (same) 4 Animal hemisphere- Meridional (makes mesomeres) [Medium meres- mesomere] Vegetal hemisphere - equatorial ( unequal division) - > will development small cells and big cells [makes micromeres and macromeres] Cells called " meres" [Small Meres- micromeres Big meres- macromeres ]
B) increases as the size of the blastomeres increases. C) decreases as the size of the blastomeres increases. D) decreases as the size of the blastomeres decreases. E) increases as the size of the blastomeres stays the same. - CORRECT ANSWER-A) increases as the size of the blastomeres decreases. epiblast - CORRECT ANSWER-fate map of bird; forms embryo blastocoel location - CORRECT ANSWER-between epiblast and hypoblast Name the three layers or groups gastrulation results in - CORRECT ANSWER-1 ectoderm- skin and nerves 2 mesoderm- connective tissues, blood, muscles, many contribution of organs 3 endoderm - linings- respiratory and digestive system At the end of gastrulation, what are we left with? - CORRECT ANSWER-3 germ layers Ectoderm - the oustide Mesoderm - the secondary mesenchyme cells and the middle of the 3 layers Endoderm - the lining of the archenteron Mechanisms by which gastrulation happen - CORRECT ANSWER-1 invagination- sea urchins 2 involution- frogs 3 Ingression 4 Epiboly- birds example of invagination- SEA URCHINS - CORRECT ANSWER-simple infolding of cells sheet in a cells
ex sea urchins ex sea urchins- in fold becomes endoderm cavity called ARCHENTERON (which becomes sea urchins digestive tract) The _____ eventually develops into the sea urchin's digestive tract. A.)blastocoel B.)archenteron C.)blastomere D.)ectoderm E.)blastopore - CORRECT ANSWER-B.)archenteron example of involution- FROGS - CORRECT ANSWER-directed infolding along another surface USED IN frogs- forms mesoderm example of ingression- - CORRECT ANSWER-migrating individual cells into embryo distinct from others since migration is into blastocoel cavitiy EXAMPLE- URCHINS, MAMMALS & BIRDS Epiboly - CORRECT ANSWER-expansion of one cell sheet over another 1 ALWAYS OCCURS IN ECTODERM 2 BIRDS: encloses yolk The movement of cells toward the blastopore is called a. mass cellular migration. b. embryonic cellular integration. c. cellular destiny. d. furrowing. e. epiboly. - CORRECT ANSWER-E epiboly
During convergent extension, A) cells on the opposite side of the embryo follow converging developmental pathways leading to bilateral symmetry. B) the cells of the neural folds adhere to one another to complete the neural tube. C) the cells of a tissue layer reorganize, forming a narrowed, elongated sheet. D) the dorsal-ventral axis is established. E) cell adhesion molecules are expressed, causing the eight blastomeres to adhere tightly to one another. - CORRECT ANSWER-C) the cells of a tissue layer reorganize, forming a narrowed, elongated sheet. Invagination of the sea urchin blastula a. is preceded by changes in the shape of individual blastomeres. (2) b. involves the filopodia of secondary mesenchyme cells. (3) c. is due to the uneven distribution of various transcriptional regulatory proteins in the egg cytoplasm. d. forms the archenteron. (1) e. All of the above - CORRECT ANSWER-E Any blastomere removed from an eight-cell mammalian embryo can develop into a normal late-stage embryo. This finding supports the idea that A) only the zygote is totipotent. B) the progressive restriction of potency hypothesis applies. C) the first cleavage event must be transverse to the animal- vegetal axis of the zygote. D) cell divisions producing the earliest blastomeres do not result in an asymmetrical distribution of cytoplasmic determinants. E) there is no organizer in mammals. - CORRECT ANSWER- D) cell divisions producing the earliest blastomeres do not result in an asymmetrical distribution of cytoplasmic determinants.
Dishelved - CORRECT ANSWER-in cytoplasm of oocyte that is destined to be partitioned into micromeres there is mrna that makes Dishelved (protein) = located in the vegetal cortex of the egg = where it prevents beta catenin from being degraded (B- catetin survival) B- catenin - CORRECT ANSWER-B-cat initiates the movement of the involuting mesoderm establishing the A/P axis of the embryo Acts as Transcription Factor beta catenin must be motile in order to enters the nucleus where it combines with promoter and enhancer to activate gene expression important in canonical wnt signaling pathway WNT SIGNALING PATHWAY (canonical) - CORRECT ANSWER-1 Wnt activates frizzle 2 Frizzle activates dishelved 3 Dishelved inhibits GSK3 (suppose to degrade Beta Caten) 4 Beta-Catenin Survives & enter nucleus and combine with another TCF! 5 Together they create Stimulatory element to activate transcription THEREFORE ACTIVATING WNT what happens in the wnt signaling pathway when wnt is absent? - CORRECT ANSWER-GSK3 will phosphorylate B- Catenin , causing it will be recognized by proteases and degraded Gastrulation in Urchins: Ingression of the Skeletogenic Mesenchyme - CORRECT ANSWER-1) After the blastula
