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level: 3.7 Mitosis

Questions and Answers List

level questions: 3.7 Mitosis

QuestionAnswer
Mitosis overview- Cell division produces two daughter cells - Have same number of chromosomes as the parent cell - Exact copy of DNA from parent
Importance of mitosis- Growth and repair - Differentiation
Stages of mitosis- Interphase - Prophase - Metaphase - Anaphase - Telophase and cytokinesis
Interphase- DNA unravels + replicates - Doubles genetic content - Organelles replicated - ATP content increases
Prophase- Chromosomes condense - Tiny bundles of proteins, centrioles, move to opposite ends of cell - Form a network of protein fibres across- spindle - The nuclear envelope breaks down and chromosomes are free in cytoplasm
Metaphase- Chromosomes (each with 2 chromatids) line up along the middle of cell - Become attached to the spindle by their centromere
Anaphase- Centromeres divide - Separating each pair of chromatids to opposite ends of the spindle - Chromatids appear v-shaped
Telophase- Chromatids uncoil, becomes long + thin again - They are chromosomes again - Nuclear envelope forms around each group of chromosomes - There are now two nuclei
Cytokinesis- Division of cytoplasm - Forms 2 daughter cells that are genetically identical
Chromatin- DNA joined to histones
How prokaryotic cells replicate- Binary fission
Binary fission process (simple explanation)- DNA replicates - Division of the cytoplasm - Forms cell wall
Binary fission process- Circular DNA + plasmids replicate - Cell gets bigger - DNA loops move to opposite ends of cell - Cytoplasm divides - Forms 2 daughter cells - Each having one copy of circular DNA but different number of copies of plasmids
How viruses use host cells to replicate themselves- Attachment proteins binds to complementary receptor proteins on host cells - Some viruses can only bind to one type of cell - Inject their DNA or RNA into host cell - Host cell organelles replicate viral particles
Investigating mitosis- Cut tip from growing root - Prepare boiling tube with 1M HCL - Put in water bath at 60*c - Transfer root tip into tube, leave for 5 minutes - Rinse root with cold water - Dry it - Cut 2mm from very tip - Place root on microscope slide - Use mounted needle to break top open - Add few drops of stain - Place cover slip, squash it down - Look at mitosis under optical microscope
How to calculate density of substance from microscopic image- No. per mm2 - Estimate field of view using a ruler - Calculate area of field of view using pie/r/2 - Count no. of stomata - No. of stomata/area - Repeat it and calculate a mean
How to calculate calibration with eyepiece graticule and micrometerWhat each eye piece is worth: - Count stage divisions (epg 10) - Calculate the actual size of the stage divisions (each is 10 micrometers) - So, 10 x 10 = 100 micrometers - Work out the size of 1 epd (total size/no. of epd) - So each epd = 1 micrometer
Using an optical microscope- Clip slide that has been prepared on the stage - Select lowest-powered objective lens - Use coarse adjustment knob to bring shape up to just below the objective lens - Look down eyepiece, move coarse + fine adjustment knob to focus it - To increase magnification, swap to a higher-powered objective lens and focus
Mitotic Index- The proportion of cells undergoing mitosis
Mitotic Index calculationMitotic index = number of cells with visible chromosomes/total number of cells observed
Graticule and micrometer- Used to calculate cell size
Using a graticule and micrometer- Line up eyepiece graticule and the stage micrometer (like a ruler) - Each division on the stage micrometer is 0.1 mm long - At this magnification, 1 division on the stage micrometer = 4.5 divisions on the eyepiece graticule - To work out size of 1 division on the eye piece graticule, divide 0.1 by 4.5 (=0.022 mm)
Example of calculation using a graticule and micrometer- If you look at a cell under the microscope at this magnification and its 4 eyepiece divisions long the calculation is 4 x 0.022 = 0.088 mm
Artefacts- Things that get in the way of observations - e.g. dust, air bubble and fingerprints - Usually made during preparation of slides