BISC 1112 Lecture Notes - Lecture 3: Prokaryote, Galactose, Muscle Hypertrophy
QUIZ 3 (3) PPT Notes: Gene Regulation BISC 1115
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Regulation of Transcription and Gene Expression in Prokaryotes and Eukaryotes
Prokaryotes
• Anaerobic- Bacteria convert milk to yogurt. Milk sugar (lactose) is used by bacteria to make ATP
and grow; Lactic acid is a by-product of this fermentation
• Inducible Genes- bacteria do not transcribe genes to use lactose unless lactose is available
• Lac Operon = regulates transcription of 3 genes. The three genes are in an operon, where all three
are transcribed together. mRNA is translated into 3 proteins needed for the bacteria to use lactose
o Gene 1 = lacZ-
-galactosidase
o Gene 2 = lacY- Lactose Permease
o Gene 3 = lacA- Transacetylase
o lacL- expressed Repressor protein- upstream, nearby gene (red).
o Lactose (green)- disaccharide sugar made of glucose + galactose. If present, it will bind to
the repressor protein (red)
o The enzyme
-galactosidase separates the two monosaccharide sugars
▪ Lactose Intolerance = people lacking - galactosidase; if a person does not
metabolize the lactose, the E. coli bacteria in their gut will produce gas
o Permease- a membrane transport protein that brings lactose into the cell
o Repressor Protein- changes shape, and is released from the operator region of the DNA, and
RNA polymerase moves in to transcribe the mRNA
o RNA Polymerase- moves in to transcribe the mRNA; and the three proteins are translated by
the ribosomes
• Degradation of prokaryotic mRNA- done over a short lifetime. Two ribonucleases are involved in
the degradation
Eukaryotes- controlling gene transcription is complicated due to the large number of genes and the
compartmentation of the chromosomes in the nucleus
• Transcription Factor (TF)- a protein that binds to a specific nucleotide sequence in DNA. Can
promote or prevent transcription
o The amino acid side chains protrude from the alpha-helix of the protein and detect the shape
of the nucleotides
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Document Summary
Regulation of transcription and gene expression in prokaryotes and eukaryotes. Prokaryotes: anaerobic- bacteria convert milk to yogurt. Milk sugar (lactose) is used by bacteria to make atp and grow; lactic acid is a by-product of this fermentation. Inducible genes- bacteria do not transcribe genes to use lactose unless lactose is available: lac operon = regulates transcription of 3 genes. Rna polymerase moves in to transcribe the mrna: rna polymerase- moves in to transcribe the mrna; and the three proteins are translated by the ribosomes, degradation of prokaryotic mrna- done over a short lifetime. Eukaryotes- controlling gene transcription is complicated due to the large number of genes and the compartmentation of the chromosomes in the nucleus: transcription factor (tf)- a protein that binds to a specific nucleotide sequence in dna. Can promote or prevent transcription: the amino acid side chains protrude from the alpha-helix of the protein and detect the shape of the nucleotides.
