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Nuclear envelope. DNA. TRANSCRIPTION. DNA. TRANSCRIPTION. Pre-mRNA. RNA PROCESSING. mRNA. mRNA. Ribosome. TRANSLATION. Polypeptide. TRANSLATION. Ribosome. (a) Bacterial cell. Polypeptide. (b) Eukaryotic cell. Comparing Prokaryotes & Eukaryotes.
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Nuclear envelope DNA TRANSCRIPTION DNA TRANSCRIPTION Pre-mRNA RNA PROCESSING mRNA mRNA Ribosome TRANSLATION Polypeptide TRANSLATION Ribosome (a) Bacterial cell Polypeptide (b) Eukaryotic cell Comparing Prokaryotes & Eukaryotes
Prokaryotic and Eukaryotic Replication C A E B G F D • In prokaryotic cells, replication starts at a single site. • In eukaryotic cells, replication starts at many sites along the chromosome.
Eukaryotes vs. Prokaryotes • Since Eukaryotes have a Double-Helix structure, the ends of the DNA strand are cut off during replication which only cuts off the telomeres • Telomeres are at the ends of DNA and protect the important DNA from being cut off but as you get older, the telomeres begin to run out • However prokaryotes are circular so they do not have the ends of their DNA cut off
Pre-mRNA Poly-A tail Cap mRNA Comparing Gene Expression in Bacteria and Animals • Bacteria and eukarya differ in their RNA polymerases, termination of transcription and ribosomes • Bacteria can simultaneously transcribe and translate the same gene • In eukarya, transcription and translation are separated by the nuclear envelope • Eukaryotic RNA transcripts are modified through RNA processing and Alternative Splicing
Intron Intron Extron 1 Extron 2 Extron 3 splicesosomes Splicesosomes are enzymes that contain RNA and remove Introns