Gene Regulation, Transcription, and Translation Practice Flashcards

Flashcards covering prokaryotic and eukaryotic transcription, translation, ribosomal structure, gene regulation, and protein trafficking to organelles.

What is the definition of transcription?

The process of synthesizing RNA from a template DNA (non-coding strand).

What was the conclusion of the Beadle-Tatum experiment regarding gene disruption?

Disruption of a gene causes enzyme deficiencies, leading to Loss of Function mutants.

What is the difference between introns and exons?

Introns are noncoding DNA regions, while exons are coding DNA regions.

Distinguish between euchromatin and heterochromatin.

Euchromatin is non-condensed and transcriptionally active, whereas heterochromatin is condensed and transcriptionally inactive.

Which specific histone proteins constitute the core octamer of a nucleosome?

Two of each of the core histones: $H3$, $H4$, $H2A$, and $H2B$.

What is the function of Histone acetyltransferase (HAT) in chromatin remodeling?

It transfers an acetyl group to a histone protein, allowing euchromatin to form.

How does methylation of cytosine in CpG islands affect gene expression?

It inhibits gene expression by enhancing chromosome compaction through methyl-binding proteins.

What is the role of insulator elements in a gene layout?

They act as boundaries between genes to ensure the correct gene gets transcribed.

Define epigenetic regulation as described in the lecture notes.

Heritable gene regulation that does not involve changes in the DNA code.

What are the specific functions of the three types of eukaryotic RNA Polymerases?

RNA Pol $I$ reads Class $I$ genes (rRNA), RNA Pol $II$ reads Class $II$ genes (mRNA), and RNA Pol $III$ reads tRNA, small rRNA, and small viral RNAs.

What is the role of the TATA Binding Protein (TBP) within the TFIID complex?

It recognizes the TATA box and causes the DNA to bend.

Which basal transcription factor is responsible for phosphorylating the $COO^{-}$ terminal of RNA Pol $II$?

TFIIH

Compare polycistronic and monocistronic transcription.

Polycistronic (prokaryotes) involves one promoter for many proteins, while monocistronic (eukaryotes) involves one promoter for one gene.

How many nucleotides must be present to code for $20$ different amino acids from $4$ nucleotides?

A minimum of $3$ nucleotides per codon, as $4^{3} = 64$ provides enough combinations.

What are the start and stop codons in the genetic code?

The start codon is $AUG$, and the stop codons are $UAA$, $UAG$, and $UGA$.

Explain the concept of "Wobble" in translation.

The first $2$ nucleotides of the codon and anticodon interact tightly, while the $3^{rd}$ (degenerate) base interaction is looser.

How do prokaryotic ribosomes recognize the start site on mRNA?

Through the Shine-Dalgarno sequence, which is complementary to the $16S$ rRNA of the $30S$ subunit.

What is the eukaryotic consensus sequence required to recognize the correct start site?

The Kozak sequence: $GCCGCC(A/G)CCACCAUGG$.

Identify the sedimentation coefficients for prokaryotic and eukaryotic ribosomes and their subunits.

Prokaryotes have $70S$ ribosomes ($30S$ and $50S$ subunits); Eukaryotes have $80S$ ribosomes ($40S$ and $60S$ subunits).

What are the three tRNA binding sites within a ribosome?

The $A$ (Aminoacyl) site, $P$ (Peptidyl) site, and $E$ (Exit) site.

What energy-coupled factors are required for translation translocation?

EF-G-GTP to drive the movement of the ribosome complex to the next codon.

How does the antibiotic Streptomycin target bacterial translation?

It changes the shape of the $30S$ portion, causing the mRNA code to be read incorrectly.

What types of proteins are synthesized by ribosomes attached to the Rough ER?

Secreted proteins, integral membrane proteins, endomembrane system proteins, and lysosomal proteins.

Which cellular organelles receive proteins synthesized by free ribosomes in the cytosol?

Nucleus, peroxisomes, mitochondria, and chloroplasts.

What is the function of the Signal recognition particle (SRP)?

It binds to the $N$-terminal signal sequence of a nascent peptide and directs the ribosome to the ER membrane.

Contrast the transport directions of COP I and COP II coated vesicles.

COP $I$ handles retrograde transport (recovering) and COP $II$ handles anterograde transport (delivering).

What proteins are involved in the docking and fusion of a vesicle to its target membrane?

SNAREs (V-SNAREs and T-SNARES).

What specific modification targets enzymes to a lysosome?

Phosphorylated mannose (mannose $6$-phosphate).

What are the roles of TOM and TIM proteins in mitochondrial trafficking?

TOM proteins allow entry into the outer mitochondrial membrane, and TIM proteins allow entry into the inner mitochondrial membrane.

What signals and factors regulate the import of proteins into the nucleus?

Nuclear Localization Signals ($NLS$) are recognized by proteins called importins.