459843
Beschreibung
Karteikarten von emma_moran, aktualisiert more than 1 year ago
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Erstellt von emma_moran
vor fast 11 Jahre
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| Frage | Antworten |
| What is the genetic information in the nucleus in the form of? | Chromatin |
| What is chromatin? | Ribbon like strands of DNA and a class of packaging proteins called histones |
| What are the chromatin threads like between divisions? | Long and randomly tangled |
| What are the chromatin threads like when a cell divides? | Shorter and very highly folded, and become visible in light microscopes as chromosomes |
| What is apoptosis? | Programmed cell death. |
| What controls apoptosis? | The activation of 'suicide genes' and bcl-2 prevents apoptosis |
| What is interphase? | When the cell isn't dividing |
| What is the mitotic phase? | When the cell is dividing? |
| What happens to the cell in interphase? | The cell grows and prepares itself for division |
| What are the different phases of interphase? | G1 phase, S phase ad G2 phase |
| What does it mean if an interphase cell is in G0? | The cell is not diving or preparing to divide. Most muscles cells and neurones are in this phase. |
| What happens in G1 phase? | Protein synthesis, vigorous growth, most of the organelles are duplicated and centrosome replication begins |
| What happens in S phase? | DNA replicates, synthesis of histones and assembly of new chromatin |
| What enzyme catalyses the process of DNA replication? | DNA polymerase |
| What happens in G2 phase? | Synthesis of enzymes and proteins essential for cell division, their transport to final site and replication of centrioles complete |
| What are the four phases of the mitotic phase in the correct order? | Prophase, metaphase, anaphase and telophase |
| What happens in prophase? | Chromatin coils and condenses into chromosomes. The nucleoli disappear and cytoskeletal microtubules disassemble. Centriole pairs separate and move to opposite ends of the cell due to the growth of new microtubules forming the mitotic spindle. |
| What does a chromosome consist of? | Two identical chromatids held together at a point called the centromere |
| Why do the chromosomes condense? | To prevent them tangling during mitosis |
| What is needed for spindle attachment? | Kinetochore |
| What happens in metaphase? | Chromosomes undergo maximum coiling and arrange themselves along the middle of the cell with the centromeres aligned at the equator of the spindle |
| What happens in anaphase? | The kinetochore of each chromatid splits. The separated chromosomes are now termed as daughter chromosomes and they move towards poles due to interaction between kinetochore and microtubules. |
| What happens in telophase? | Begins after identical sets of chromosomes are at the opposite poles. Chromosomes uncoil and transform into chromatin. Nuclear envelope reforms around the chromatin mass. Nucleoli reappear and spindle disappears. This is the end of karyokinesis (nucleus division) |
| Which is the longest sub phase of mitosis? | Prophase |
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Image:
metaphase (image/jpg)
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Metaphase |
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Image:
telophase (image/jpg)
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Telophase |
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Image:
anaphase (image/jpg)
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Anaphase |
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Image:
prophase (image/jpg)
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Prophase |
| What happens in cytokinesis? | The cytoplasm develops a cleavage furrow that deepens, finally separating the two daughter cells, each with the same complement of chromosomes as the parent cell. |
| When does cytokinesis occur? | It starts during late anaphase and continues through telophase and beyond. |
| How is cell density controlled? | Cell growth and division, cell death (apoptosis) and G0 phase |
| What regulates the initiation of cell growth? | Cyclin dependent kinases (Csk's) |
| How are cyclin dependent kinases switch on and off? | The presence of cyclin |
| What are cell checkpoints ? | Control mechanisms that ensure the reliability of cell division. They verify whether the processes at each phase of the cell cycle have been accurately completed. |
| What happens at the restriction point at the end of G1? | Cells that should cease division exit the cell cycle and enter G0 |
| How do continually dividing cells overcome the restriction point at the end of G1? | Growth factor induced expression of cyclin D proteins |
| How does the restriction point at the end of G1 prevent cell division? | By the action of CKI p16 & p21. they inhibit CDK4/6 so it can no longer interact with cyclin D1 to cause cell progression. |
| How do active CDK4/6-cyclinD complexes allow G1-S phase transition? | The phosphorylate the tumour supressor Rb, which relieves the inhibition of transcription fcator EF2. EF2 can then cause expression of cyclin E, which interacts with CDK2. |
| Where is the second checkpoint located? | At the end of G2 phase, triggering the start of M phase |
| When does the mitotic spindle check point occur? | The point in metaphase where all the chromosomes should be aligned at the mitotic plate and be under bipolar tension. |
| How does the mitotic spindle checkpoint work? | The tension created by the bipolar attachment is what is sensed, which initiates the anaphase entry |
| How do tumours occur? | The loss or damage of tumour suppressor genes or the activation of proto-oncogenes |
| What effect do mitotic inhibitors have? | Affect microtubules in metaphase of the cell cycle |
| What are mitotic inhibitors used for? | They are used to treat tumours but the also kill other rapidly dividing cells such as hair. |
| What are telomeres? | Caps on the end of chromosomes. |
| What happens to telomeres in replication? | They decrease in length every time |
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