Q) Describe the structure of chromosomes before and at the beginning of mitosis
Main points | |
Key idea: | Long thread-like chromatin during interphase prior to mitosis |
·Chrom exists as indistinct thread-like chromatin ·Ref to DNA mol coil around a set of 8 histone proteins, form nucleosome struc | |
Key idea: | Condensation of chromosomes during prophase |
·Ref to histone associates w linker DNA ·Causes adjacent nucleosomes to pack tog, form solenoid or 30nm diameter fibre ·30nm solenoid fibre will undergo further coiling ·Ref to higher order coiling by interacting w scaffolding proteins, form condensed chrom | |
Key idea: | Formation of the double structure of (condensed) chromosomes by metaphase |
·Ref to double struc of chrom made up of 2 sister chromatids joined at centromere ·Ref to genetically identical sis chromatids due to DNA replication (during S-phase of interphase) ·Ref to spindle binding to centromere via kinetochore that position chrom at metaphase plate & subseq separate sis chromatids during anaphase | |
Comments: (i) Visualize the answer with the aid of a labelled diagram. (ii) Verbalize the answer + write down the main points w/o referring to the answer (use abbreviations) (iii) Read again within the next 24h & once more within 72h (do not spend more than 10min) (iv) Cross reference to previous essay answer (behaviour of chromosomes during meiosis) and compare in terms of similarities and differences | |
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