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level: 1.6 cell division

Questions and Answers List

level questions: 1.6 cell division

QuestionAnswer
What is the cell cycle? (8)events which lead to the cell dividing into 2 daughter cells Interphase - happens before division has 3 stages: G1 =cell growth and metabolism S = DNA replication G2 = Cell growth and preparation M Phase - cells divide to create 2 daughter cells 2 stages: Mitosis = nuclear division Cytokinesis = cytoplasmic division
What is mitosis?process of nuclear division whereby copied DNA molecules are arranged into 2 nuclei
What happens during interphase? (4) DOCTDNA replication (DNA copied during the S phase) Organelle duplication (organelle copied for twin daughter cells) Cell growth (cytoplasmic volume increases before division) Transcription / translation (key proteins and enzymes are synthesised)
How is DNA usually packed in the nucleus? (2)chromatin = loosely packed in an accessible form in the nucleus can be transcripted and translated
How is DNA packaged before cell division? (4)chromosome = chromatin supercoils to become tightly wound and condensed easily grouped but inaccessible for transcription condenses in prophase decondenses in telophase
How is DNA packed during the S phase in interphase? what happens after? (2)during S phase, the chromosome has 2 identical DNA strands (sister chromatids) which is held in the middle with centromere During mitosis when they separate they are each made of a single DNA strand = daughter chromosomes
What are the 4 stages of mitosis? PMATProphase Metaphase Anaphase Telophase division of cell in two (cytokinesis) is after the final stage
What happens during interphase? (3)DNA is uncondensed (Chromatin) and is in the nucleus organelles are duplicated cell is enlarged for division
What happens during prophase? (PRO = before) (3) spindlesDNA supercoils and chromosomes condense (made of identical sister chromatids) paired centrosomes moved to the opposite poles of the cell and form microtubule spindle fibres nuclear membrane breaks down
What happens during metaphase? (MIDDLE) (3)Chromosomes align in the middle microtubule spindle fibres connect to the centromeres of each chromosome spindle fibres contract bec of microtubule depolymerisation
What happens during anaphase? (AWAY) (2)sister chromatids separate and move to opposite poles of the cell because of spindle fiber contraction
What happens during Telophase? (3)spindle fibres dissolve chromosomes decondense nuclear membrane reforms around the 2 chromosome sets
What happens during cytokinesis?LAST STAGE: cytoplasmic division whereby the cell splits into 2
Describe cytokinesis in animal cells? (3)microtubule filaments form a ring (cleavage furrow) which contracts in the center of the cell cells become PINCHED off = 2 cells are formed cells separation = centripetal (starts outside and moves to the centre)
Describe cytokinesis in plant cells?vesicles form at the centre of the cell and fuse to form an early c plate cells separation = centrifugal
What is the mitotic index? what is it used for? (3)a measure of the proportion of dividing cells mitotic index increases during cell division is used to predict the response to chemotherapy from cancer cells
mitotic index formulacells in mitosis / total cell number
How would you identify mitotic cells?they lack a clearly defined nucleus and the condensed chromosomes are visible P = chromosomes are condensed in a nucleus M = chromosomes are aligned in the middle A = 2 clusters of chromosomes at poles of the cell T = 2 nuclear regions in a single cell
Functions of mitotic division (TOAD)Tissue repair = damaged / aged cells are replaced with new cells Organismal growth = multicellular organisms make new cells Asexual reproduction = natural cloning (vegetative propagation) Development of embryos = zygotes divide and differentiate to form embryos
What are the cell cycle checkpoints to regulate the cell cycle? (3)G1 = checks if the cell is ready for DNA replication (S phase) G2 = checks if the cell is ready for mitosis M = checks that the cell is ready for cytokinesis
What are cyclins? What do they activate? what do they do? (4)1) family of regulatory proteins that control cell cycle progression 2) activate cyclin dependent kinases (CDK) by forming a complex with it 3) The complex phosphorylates a target protein = a specific cell cycle event 4) After the event the cyclin is degraded and CDK inactivated
Why do cyclin concentrations need to be tightly regulated? (3)to make sure the cell cycle happens in a proper sequence diff cyclins bind and activate diff CDKs cyclin levels peak when their target protein is needed for function and remains at lower levels at other times
How does cell death occur?once cells reach their proliferative capacity = cell division stops
What is the aging phase for cells called?senescence (aging) phase = cell death
What are the two different types of cell deaths?cell death can be uncontrolled (necrosis) or programmed (apoptosis)
What is the difference between apoptosis and necrosis (2)Apoptosis - controlled destruction of a cell in response to molecular signals uses mitochondrial proteins cell contents are packaged into vesicles and recycled Necrosis - premature death due to injury or nutritional deprivation cells becomes destabilised Cell contents are released into tissues = inflammation
What is cancer?uncontrolled cell division and can occur in any tissue or organ
What is a tumor? 2 typesthe abnormal cell growths formed from cancer (uncontrolled cell division) Primary = stay in the original tissue (BENIGN GROWTHS) Secondary = invade neighboring tissues (MALIGNANT GROWTHS)
What is metastasis?spread of cancerous tissue from one place to another
How are secondary tumors defined?defined and treated according to the original cell type eg: breast cancer spreads to liver = secondary breast cancer of the liver
What is a mutagen? example? (4)an agent that causes a change in the genetic material of an organism either acts on the DNA or replicative machinery can be physical, chemical or biological carcinogens = formation of cancer
Examples of physical mutagens? (Radiation) (3)X-rays (ionising) = medical UV (sunlight) radioactive decay
Examples of chemical mutagens? (3)Carcinogen (cigarettes) processed foods cleaning products
What is the mutagen that leads to the formation of cancer?carcinogens
What are examples of biological mutagens? (3)viruses (HPV) bacteria (helicobacter) mobile genetic elements (transposons)
What is an oncogene?a gene that could cause cancer
Which mutations to 2 genes causes cancer?proto-oncogenes = code for proteins that increase cell growth When mutated: cancer causing oncogene tumor suppressor genes = code for proteins that repress cell cycle progression and promotes cell death = if mutated or undergoes increased expression it becomes a cancer causing oncogene
What is the correlation between smoking and lung cancer?There is a positive correlation 90% Cancer rates are higher in countries with higher rates of smoking increases risk of other cancers such as mouth, stomach, liver
how many chemical compounds are there in cigarettes and how many are carcinogenic?4000 , 60+ carcinogenic