MCB*2050 Midterm Prep Exam Questions and Answers 100% Solved

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MCB*2050 Midterm Prep Exam

Questions and Answers 100% Solved


RNA polymerase I - ✔✔- in nucleus of eukaryotic cells

- transcribes Pre-rRNA (28S, 18S, 5.8S rRNAs)

- make ribosome components and synthesize proteins

RNA polymerase II - ✔✔- in nucleus of eukaryotic cells

- transcribes mRNA,

snRNAs, siRNAs, and miRNAs

- encodes protein, RNA splicing, chromatin-mediated repression, and

translation cotrol

mRNA - ✔✔- messenger RNA

- transcribed by RNA polymerase II

- encodes protein

snRNAs - ✔✔- transcribed by RNA polymerase II

- small nuclear RNA

- RNA splicing

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siRNAs - ✔✔- transcribed by RNA polymerase II

- small interfering RNAs

- chromatin-mediated repression and translation control

miRNAs - ✔✔- transcribed by RNA polymerase II

- micro-interfering RNAs

- translation control

RNA polymerase III - ✔✔- in nucleus of eukaryotic cells

- transcribes tRNAs, 55 rRNA, snRNA U6, 7S RNA, and other small stable

RNAs

- they encode for proteins, form a ribosome component, perform RNA

splicing, create a signal recognition particle for insertion of polypeptides

into the endoplasmic reticulum, and other functions

tRNAs - ✔✔- transcribed by RNA polymerase III

- transfer RNA

- synthesize proteins

5S rRNAs - ✔✔- transcribed by RNA polymerase III

- the ribosome component

- synthesize proteins

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snRNA U6 - ✔✔- transcribed by RNA polymerase III

- splice proteins

7S RNAs - ✔✔- transcribed by RNA polymerase III

- signal recognition particle for insertion of polypeptides into the

endoplasmic reticulum

Control of gene expression in bacteria - ✔✔· Prokaryote gene

expression is regulated primarily by mechanisms that control transcription

· In prokaryotes one enzyme, RNA polymerase, transcribes all genes

· A group of proteins called sigma-factors recognize promotor elements (-

10, -35) and load RNA polymerase at the start site

· An operon is a group of genes that are all transcribed together with one

common promoter, so either all of the genes are transcribed or none of the

genes are transcribed (e.g. the lac operon)

· It is regulated by activator proteins (CAP, Catabolite Activator Protein)

that bind next to a promoter and recruit RNA polymerase

· Bacterial gene expression is regulated by transcriptional activators and

repressors

sigma-factors - ✔✔- recognize promotor elements (-35, -10) and load

RNA polymerase at the start site

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lac operon in bacteria - ✔✔- lac operon is a regulated promoter

- it is regulated by catabolite activator proteins (CAP) that bind next to a

promoter to recruit RNA polymerase

- it is repressed by the lac repressor which binds downstream of the

transcription initiation site

lac operon (- lactose, + glucose) - ✔✔- glucose is the preferred source of

energy so when it is present, there are low levels of cyclic AMP (cAMP)

and the lac repressor is bound downstream of the promoter site

- this inhibits the binding of the polymerase

lac operon (+ lactose, +glucose) - ✔✔- the lac repressor is activated in

the presence of lactose

- the 4 binding sites of the lac repressor are each bound by lactose

- this releases the lac repressor from blocking the transcriptional initiation

site

- transcriptional rate is low because there is still a presence of glucose and

therefore, the cAMP isn't bound

- glucose is still being metabolized