2741374
Description
Flashcards by Afronewtzz, updated more than 1 year ago
|
Created by Afronewtzz
over 9 years ago
|
|
| Question | Answer |
| Describe what is meant when we say that homologous proteins function interchangeably in the development of mice and flies. | - A fly protein used in a mouse. - DNA sequence from Drosophila (species of fly) coding for the Engrailed protein can be substituted for the corresponding sequence coding for the Engrailed-1 protein of the mouse. - Loss of Engrailed-1 protein in the mouse causes a defect in its brain/ the cerebellum fails to develop. - The transgenic mouse can be effectively rescued from this deformity. |
| Define embryogenesis. | The formation and development of an embryo. |
| What is cell proliferation? | Cell division |
| What was determined from Long term imaging of zebrafish about embryonic development? | - Labelled nuclei. - Cells were watched and it was found that cells formed and specialised in the head first. - Cells then moved down through the centre of the embryo and it was judged where they went to specialise and differentiate (where they originated and moved). |
| What is gastrulation? | Early embryonic development (one of the first stages) in which the signle-layered blastula is reorganized into the 3-layered gastrula = ectoderm, mesoderm and endoderm. |
| What organism do we study in order to analyse gastrulation? | Sea urchin |
| Describe the main stages of Gastrulation. | 1. Endoderm begins to invaginate on the blastula. 2. Some cells break free and become the primary mesenchyme. 3. More cells break free and migrate, forming secondary mesenchyme on top of the endoderm. 4. Invagination is lengthened by contraction of secondary mesenchymal filopodia. 5. Gastrula is formed. |
| Once gastrulation has complete (blastula > gastrula)... describe what the different segments of the gastrula will become. | - Mesoderm = Future skeleton - Archenteron = Gut tube - Blastopore = Future anus - Where archenteron meets ectoderm = Future mouth. |
| What are regulatory genetic elements and what are their role in development? | - Regions of non-coding DNA which regulate the transcription of nearby genes. - Allows the expression of certain genes at certain times during development, whilst inhibiting others. |
| What is Lineage tracing? | The identification of all progeny of a single cell through labelling. |
| Describe the following image.... | - Experimental embryology. - 2-cell embryo split almost in 2 by hair loop. - Same structures, but just with 2 heads. |
| What is experimental embryology? | - Cells and tissues from developing animals are removed, rearranged, transplanted or grown in isolation in order to discover how they influence one another. - Decipher cell-cell interactions and rules of cell behaviour. |
| Describe the following image... | - Experimental Embryology - An amphibian embryo at a later stage in development receives a graft of a small cluster of cells from another embryo at that stage. - Develops into conjoined twins. |
| What is fate determination? | - By simply watching closely (or with the help of a tracer dye), one can discover what the fate of a given cell in an embryo will be if that embryo is left to develop normally. |
| Describe the following types of fate determination: - Normal fate - Not determined - Determined | - Normal fate : All cells go to their expected environments and differentiate. - Not determined : The cell has no destined cell-type; it will become identical to whatever cells are around it based on the surroundings it is exposed to. - Determined : A cell will become the same cell it is destined to regardless of the surroundings trying to effect it. |
| Describe the following results when cell's of an undetermined cell fate and a determined cell fate are transplanted to altered environments. | - If a cell has an undetermined cell fate and is transplanted to a different environment to normal, it can become like the cells it is surrounded by and have no adverse affect on the development of the embryo. - If a cell has a determined cell fate and is transplanted into an abnormal environment, it will still develop into its specialised cell type regardless, and can have adverse affects on the development of the embryo since it is not performing the expected function of the tissue in that area. |
| What is meant if it is said that a cell is not determined, but specified or committed? | The cell is somewhat specialised for its normal fate, with a strong tendency to develop in that direction, but still able to change and undergo a different fate if required. |
| What is often a big cofactor in the ability of a cell to remain determined to the cell function it is destined for? | The mutual support of surrounding cells and their specialised character, hence why if a cell is isolated from its companions, it can lose its destined function. |
| What is meant when many cells are described as remembering their positional values at certain locations in the body? | - Before a cell has become committed to differentiating as a specific cell type, they become regionally determined - they switch on genes to mark their position in the body. - A.k.a. Positional value. |
| Describe how the Chick-Embryo model displays features of cell's positional value. | - A small block of undifferentiated tissue at the base of the leg bud, from the region that would normally give rise to part of the thigh, can be cut out and grafted into the top of the wing bud. - The graft forms not the appropriate part of the wing top, nor a misplaced piece of thigh tissue, but a toe. - The early leg bud cells are already determined as leg but are not yet irrevocably committed to form a particular part of the leg. |
| How does the Chick model of embryos at 6 days, showing the limb buds with probes to detect expression of Tbx4 and Tbx5 displays features of cell's positional value in the body? | Cells expressing Tbx4 = Form a leg Cells expressing Tbx5 = Form a wing Tbx4, when artifically misplaced in the wing bud, causes the limb to develop with leg-like characteristics. |
| What is an 'inductive interaction' in cell development? | - Signals from neighbouring cells. - Cells start out by having the same developmental potential, and a signal from cells outside the group then drives one or more of the members of the group into a different developmental pathway, thus changed character. - The signal is limited to time and space so only some of the cells/ those closest to the signal take on this induced character. |
| What is asymmetric and symmetric division? | Asymmetric = Unequal division of cell - 2 sister cells are not identical. Symmetric = Cell is evenly divided and sister cells are initially, identical. |
| Name 2 origins of asymmetry between sister cells. | - Asymmetric division (sister cells are born differently). INTRINSIC - Sister cells become different/ asymmetric as a result of influences acting on them after birth. EXTRINSIC |
| What is meant by asymmetry through positive feedback? | - 2 cells interact; each producing a substance that acts on the other cell - transient bias arises randomely and creates slight asymmetry. - An increase of the substance in one of those cells leads to a positive feedback that tends to increase the substance in that cell still further, whilst decreasing it in its neighbour. - 2 cells become radically different. - The small influence that initially directed the choice is no longer required to maintain it - stable memory. |
| Describe the principle of asymmetry in stem cells. | - When a stem cell divides into 2 daughter cells, one of the 2 cells will always self-renew and remain a stem cell in order to maintain the population of stem cells... - The other will terminally differentiate into a specialised function. |
| When a stem cell asymmetrically divides, one daughter cell is self-renewed, the other goes on to become a committed transient amplifying cell... what does this mean? | - They are committed to their fate. - They can only go on to be a certain type of cell - cannot go back to being pluripotent. |
| In what way can pluripotent embryonic stem cells be differentiated into diverse cell types after being cultured in vitro? | Through addition of a couple of hormones denoting their different pathways. |
Want to create your own Flashcards for free with GoConqr? Learn more.