1
Q
Genome
A
- Encodes the information to construct & maintain an organism
- Most genomes made of DNA
2
Q
What do you need to release the biological info stored in the genome?
A
- Gene expression (transcription/translation)
3
Q
Transcriptome
A
- 1st product of genome expression (transcription: DNA to RNA)
- The repertoire of RNA molecules present in a cell at a particular time
4
Q
What is used to view the transcriptome/RNA molecules?
A
- DNA microarray
- Recently, RNA sequencing
5
Q
A
6
Q
Proteome
A
- 2nd product of genome expression (translation: RNA to protein)
- Collection of proteins in a cell
7
Q
Process of translation
A
- Ribosomes translate RNA to proteins (amino acids linked)
8
Q
What is used to view the proteome/protein molecules?
A
- 2D gel electrophoresis
- Separated by size & isoelectric point (ph = neutral)
9
Q
What produces difference cell types from the same genome?
A
- Differences in genome expression
10
Q
How many genes are expressed at any one time?
A
- 30-60%
10
Q
Regulation of genome expression pathway
A
- Genome (DNA) organized & compacted into chromatin
- Transcriptome (RNA) spliced by introns & exons
- Proteome (Protein) sorted, activated, and localized to the correct organelles
11
Q
Regulation of gene expression is crucial for:
A
- Defining cell types (diff cell types = diff transcriptomes) –> multicellular organisms
- Responses to extracellular (environment) stimuli –> multicellular & unicellular organisms
12
Q
Prokaryotic transcription pathway
A
- Sigma factor binds to RNA polymerase, promoter positions it and indicates transcription start site
- DNA unwound until it reaches promoter, transcription occurs downstream of promoter
- Sigma factor released once approx 10 nucleotides synthesized
- Transcription elongation until termination (coded in DNA, forms hairpin to stop RNA polymerase)
- RNA binds to start again
13
Q
Gene regulatory proteins
A
- Regulate gene expression in prokaryotes & eukaryotes
- Transcription factors bind specifically to cis elements (regulatory regions of DNA)
- Turn genes on = activators
- Turn genes off = repressors
14
Q
Operon
A
- Multiple genes can be transcribed into a single RNA molecule
15
Q
Tryptophan (trp) operon
A
- 5 genes in 1 RNA molecule
- Encode enzymes for tryptophan biosynthesis
16
Q
2 protein-bound states in trp operon promoter
A
- Bound by RNA polymerase (trp gene expression on)
- Bound by tryptophan repressor protein (trp gene expression off), binds specific DNA sequence of the promoter called an operator
- Repressor must bind 2 molecules of tryptophan to bind to DNA
17
Q
What happens when tryptophan is low?
A
- Inactive repressor
- RNA polymerase binds to make more tryptophan
- Operon is on
18
Q
What happens when tryptophan is high?
A
- Active repressor
- RNA polymerase doesn’t bind
- Operon is off
19
Q
Structure of tryptophan repressor
A
- Helix-turn-helix DNA binding motif (binds in the major groove of DNA double helix)
- Tryptophan induces conformational change so it can bind to major groove
- Doesn’t let RNA polymerase bind
20
Q
Lac Operon
A
- 3 genes in 1 RNA molecule
- Enables the use of lactose in the absence of glucose
21
Q
Lac Activator
A
- Catabolite Activator Protein (CAP)
- Promotes Lac expression (low glucose & high lactose)
22
Q
Lac Repressor
A
- Lac Repressor Protein
- Inhibits Lac expression (low lactose, so doesn’t produce genes to use lactose)
23
Q
Where does CAP bind in Lac Operon?
A
- Cis-regulatory sequence
- Upstream of promoter
24
Where does Lac repressor bind?
- Lac operator
- Downstream of promoter
25
What does the 1st gene of Lac operon encode?
- B-galactosidase
- Breaks down lactose to glucose and galactose
26
What happens when Lactose levels are low?
- Lac repressor is bound to the operator so RNA polymerase can't bind
- Lac operon gene expression is off
27
What does an increase in lactose do?
- Increases allolactose which binds to Lac Repressor to release it from operator
- Then CAP binds to allow RNA polymerase to turn on expression of lac operon
28
What does decreasing glucose levels do?
- Increase cyclic AMP (cAMP) which binds CAP protein to cis sequence
BIO230 Part 1
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