Cell and Molecular Biology Flashcards

Which enzyme is responsible for unwinding the DNA double helix during replication?

Answer: Helicase

Helicase breaks hydrogen bonds between base pairs to unwind the double helix at the replication fork.

The signal recognition particle (SRP) directs ribosomes to which cellular structure?

Answer: Rough endoplasmic reticulum

SRP recognizes signal sequences on nascent polypeptides and docks the ribosome-mRNA complex to the rough ER membrane.

Which type of RNA splicing involves the formation of a lariat intermediate?

Answer: Group II intron splicing

Group II intron self-splicing and spliceosomal pre-mRNA splicing both form a lariat intermediate via a 2'-5' phosphodiester bond.

Which cell junction allows direct cytoplasmic communication between adjacent animal cells?

Answer: Gap junctions

Gap junctions are formed by connexin proteins that create channels allowing ions and small molecules to pass between cells.

What is the primary role of ubiquitin in protein degradation?

Answer: It tags proteins for destruction by the proteasome

Polyubiquitin chains attached to lysine residues serve as recognition signals that target proteins for 26S proteasomal degradation.

During mitosis, kinetochore microtubules attach to chromosomes at which structure?

Answer: Centromere

The kinetochore is a protein complex assembled on the centromere that captures spindle microtubules during cell division.

Which process describes the movement of a transposable element by copying itself and inserting the copy elsewhere?

Answer: Replicative transposition

Replicative transposition duplicates the transposable element, leaving the original in place and inserting a copy at a new site.