Gene Expression Lesson Review Flashcards
A review from the Gene Expression lesson. (22 cards)
What are some examples of us needing Gene Regulation?
- Post-Workout, accelerates muscle recovery.
- During mensuration/pregnancy, you need more of some proteins and less of others.
- During illness (anti-bodies are proteins).
- Protein hormones (TSH, GH, insulin).
When should GENES be TRANSCRIBED?
It should only be transcribed when that protein is necessary, otherwise it would be a waste of energy.
What are the LEVELS of CONTROL (EUK)?
- Transcriptional: transcription factors
- Post-transcriptional: intron/exon
- Translational: not all mRNAs are translated
- Post-translational: activation is controlled
What do Operons control and where are they found?
- Found mostly in PROK.
- Controlled by:
- Regulatory protein
- Promoter seq + operator seq; both are upstream from the gene, non-coding.
What are the CLUSTERS of genes after the non-coding region?
- Lac Operon
- Trp Operon
What is the Operon structure consist of?
It consists of:
- Regulator Gene
- Promoter Region
- Operator Region
- and genes coding for the 5 enzymes needed to synthesize tryptophan.
What is a LAC OPERON?
It is:
- Dissacharide (Lactose)
- Found in dairy products (ex milk, cheese)
- B-galactosidase: splits it into 2 monomers
- Only needed if lactose is present
- Gene for the enzyme can be turned off if lactose is not present.
What are the 3 genes that are required for lactose metabolism?
- LacZ: B-galactosidase
- LacY: B-galactoside permase
- LASTLY LacA: B-galactoside transacetylase
What happens when there is an ABSENCE of LACTOSE?
- Lacl: Repressor protein.
- Lacl binds to operator (complementary).
- Physically prevents binding of RNA polymerase.
- Effectively prevents transcription.
What happens when there is a PRESENCE of LACTOSE?
- Lactose binds to Lacl repressor protein.
- Lacl changes conformation.
- Can no longer bind to operator/promoter.
- Allows for transcription.
What does EFFECTOR mean?
It is the level of lactose (controls gene expression).
What does INDUCER mean?
It is lactose which induces transcription.
What does POSITIVE CONTROL mean?
It means it has a presence of molecules which turns genes ON.
What does ENZYME INDUCTION do?
The lactose would bind to the repressor protein to INDUCE gene expression.
What is needed to synthesize proteins in TRYPTOPHAN?
- Aa is needed to synthesize proteins.
- Genes are represented if trp is present
- Genes are induced if trp is absent
- 5 genes –> 5 polypeptides
- It would result in 3 ENZYMES.
What happens when there is a PRESENCE of TRP?
- tryptophan would bind to the repressor protein
- New conformation –>active
- Tryptophan - repressor complex binds DNA operator sequence
- Prevents gene expression
What happens in the ABSENCE of TRP?
- Trp-repressor complex falls apart
- falls of the DNA operator
- Allows RNA pol to bind and transcribe genes
- enzymes can function to synthesize trp since it is lacking.
What does EFFECTOR mean (trp Operon)?
It is the level of trp (controls gene expression).
What does COREPRESSOR mean?
It represses transcription along with the repressor protein in trp.
What does NEGATIVE CONTROL mean?
It means that the presence of trp turns genes OFF.
What does the Presence in trp do?
It represses transcription of TRP.
What does NEGATIVE CONTROL mean?
It is the presence of trp which turns genes OFF
