BIOL10005 Lecture Notes - Lecture 17: Protist, Sexual Selection, Plant
31 Oct 2018
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Document Summary
Polymorphism is maintained -> (cid:862)fittest(cid:863) for(cid:373) cha(cid:374)ges over time. At first experiment, most brown snails were eaten / yellow snails remained. In next generation, the number of yellow snails increased -> birds feed on yellow snails. Example of negative frequency-dependent selection (fitness declines as frequency of the phenotype increases) > packaging of dna in chromosomes (histones, supercoiling) Bacterial chromosome attaches to the plasma membrane. Chromosomal dna replicates, and the attachment points separate. Circular dna structure only allows for 1 origin of replication. Invagination of the cell membrane -> prokaryotic nuclear membrane. Nuclear envelope is rer pressed up against the dna. Ribosomes can insert proteins into the empty space of rer. Origin of the nuclear membrane -> endoplasmic reticulum. During nuclear division, nuclear envelope disintegrates -> after chromosomes divide & separate, er clusters around the chromosomes -> new er formed. Mitochondria has its own membrane & dna.
