Bio Exam

What enzyme synthesizes RNA?

RNA polymerase

In what direction is RNA synthesized?

5′ to 3′

Which DNA strand is used during transcription?

Template strand (3′ → 5′)

What is added to the 5′ end of eukaryotic mRNA?

5′ methyl-G cap

What is added to the 3′ end of eukaryotic mRNA?

Poly-A tail

What removes introns from pre-mRNA?

Spliceosome

Do prokaryotes couple transcription & translation?

Yes

Where does translation occur in eukaryotes?

Cytoplasm on ribosomes

What is the start codon?

AUG (methionine)

What binds the start codon first?

Initiator tRNA (Met)

What is the A site?

tRNA binding site for next amino acid

What is the P site?

Holds growing polypeptide chain

What binds stop codons?

Release factor

Why is the genetic code redundant?

Multiple codons code for same amino acid

How many bases per codon?

3

21 bases of mRNA code for how many amino acids?

7

What is a point mutation?

Single nucleotide change

What is a silent mutation?

Mutation with no amino acid change

What is a missense mutation?

Mutation causing one amino acid change

What is a nonsense mutation?

Mutation making a premature STOP codon

What is a frameshift mutation?

Insertion/deletion not divisible by 3

What is a promoter?

DNA site where RNA polymerase binds

What are transcription factors?

Proteins that regulate transcription

What is an operon?

Group of prokaryotic genes under one promoter

What inactivates the lac repressor?

Allolactose

When is the lac operon MOST active?

Lactose present + glucose absent

What does CAP–cAMP do?

Boosts transcription when glucose is low

Operator moved far downstream → result?

Operon always ON

What does histone acetylation do?

Increases gene expression

Histones resistant to acetylation → result?

Decreased gene expression

How proto-oncogenes become oncogenes?

Mutation, amplification, or translocation

Genes mutated in cancer?

Proto-oncogenes + tumor suppressor genes

Why chemo causes side effects?

Kills healthy fast-dividing cells

High ubiquitin indicates?

High protein degradation

Electron flow in aerobic respiration?

Glucose → NADH → ETC → O₂

Final electron acceptor in respiration?

Oxygen

Which process releases the most CO₂?

Citric acid cycle

Which process makes the most ATP?

Oxidative phosphorylation

Both fermentations regenerate what?

NAD⁺

Product of lactic fermentation?

Lactate

Final electron acceptor in alcoholic fermentation?

Acetaldehyde

What does glycolysis produce?

Pyruvate

What determines an organism’s traits?

Nitrogenous base sequence

Why skin vs liver cells differ?

Different genes expressed

How to experimentally increase ATP synthesis?

Lower pH outside mitochondria

What happens when trp repressor binds tryptophan?

Operon OFF

Where does oxidative phosphorylation occur?

Inner mitochondrial membrane

Where does the Krebs cycle occur?

Mitochondrial matrix

mRNA function?

Carries code from DNA to ribosome

tRNA function?

Delivers amino acids to ribosome

rRNA function?

Forms ribosome + catalyzes peptide bonds

What tags proteins for destruction?

Ubiquitin