Biology 2581B Chapter Notes - Chapter 2: Archaea, Zygote, Chloroplast Dna

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10 Jan 2018
Wednesday, January 10, 2018
Lec #2 Readings
An early RNA world!
-life requires 2 functions: able to store genetic material, ability to catalyze rxns within
body. !
-these 2 distinct functions are handled by either DNA OR enzyme/proteins. !
-since DNA and protein’s existence relies on each other, they could not have started
-RNA started life— it serves as both a catalyst (aka ribozymes), and stores genetic
ribozymes allows replication of RNAs, and synthesis of protein from the RNA. !
began life on earth !
-eventually, RNAs were able to synthesize a protein that acts as an enzyme— since
enzymes are more ecient than ribozymes, selection favours protein for catalytic
-RNA became focussed to the role of information storage. Eventually outcompeted
by DNA since DNAs are more stable and have a more accurate replication process. !
Introns — early/ late hypothesis!
-introns are thought to be only present in eukaryotes. But are actually seen in some
prokaryotes, as well as mitochondrial/ chloroplast genomes. !
-size and number of introns are directly related to organism complexity. !
-all rRNA/ tRNA/ mRNA genes may contain introns!
-introns tend to be longer, and more frequent than exons!
-most introns are non-coding — an intron of a gene is unlikely to be the exon of
another gene. But an exon of a gene COULD be an intron for another gene
Intron late hypothesis
- introns were non existent, but later acquired by eukaryotes. !
Intron early hypothesis
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