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UNIT 6 AS BIOLOGY
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What are the steps in DNA packaging?
What are the steps in DNA packaging?
DNA double helix: the length of the DNA molecule in an average human chromosome is about 4.8cm long--------------------------------------------------------
Nucleosome fibre: the DNA is wrapped around histone proteins, forming chromatin. Histones associate in octamers to form “beads-on-a-string” structures called nucleosomes. These are the basic unit of chromosomes-------
Solenoide fibre: more histones help the nucleosome fibre form a tightly-coiled structure called a solenoid fibre--------------------------------------------------
Folded/coiled solenoid fibre: the solenoid fibre is thought to wrap and coil around scaffolding proteins, but the exact mechanism of this is not known-----
Supercoiling: to reduce the stress on the molecule, the solenoid fibre twists and writhes, like a curly telephone cable. The sum of this twisting and writhing is supercoiling--------------------------------------------------------------------
Chromosome: the DNA molecule is packed so much that the average human chromosome is just 6μm long. Here, the chromosome has replicated so it contains two DNA molecules
What are the three types of DNA replication?
What are the three types of DNA replication?
Semi-conservative replication: two strands of DNA unwind from each other, and each act as a template for synthesis of a new, complementary strand. This results in two DNA molecules with one original strand and one new strand----
Conservative replication: DNA replication in this model results in one molecule that consists of both original strands, and another molecule that consists of two new strands with exactly the same sequences as the original molecule-------------------------------------------------------------------------------------
Dispersive replication: DNA replication results in two DNA molecules that are mixtures of parental and daughter DNA. In this model, each individual strand is a patchwork of original and new DNA
What is binary fission and its steps?
What is binary fission and its steps?
Binary fission is the process by which prokaryotic cells divide and reproduce
1. DNA/Plasmid replicates and attaches to membrane
2. Cell membrane grows through the middle
3. Cell wall forms and splits cell
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