Nucleus, DNA Packaging, Gene to Protein, and Cell Cycle Concepts

These flashcards cover key concepts related to the nucleus, DNA packaging, the process of gene to protein, and the cell cycle and mitosis.

What are the main parts of the nucleus and its core job?

Nuclear envelope, chromosomes (chromatin), nucleolus. Job: store DNA and control gene regulation.

What is chromatin made of?

DNA wrapped around histone proteins.

What happens in the nucleolus?

rRNA is made and ribosomal subunits are assembled.

What happens at translation termination?

A stop codon is reached; a release factor frees the new polypeptide.

Why is post-translational modification necessary?

It folds/chemically modifies proteins so they become functional.

Why do different cell types make different proteins if they have the same genes?

Differential gene expression—cells turn specific genes on/off based on type and conditions.

Define triplet vs codon.

Triplet = 3-base DNA sequence; codon = matching 3-base mRNA sequence.

Briefly outline transcription.

Initiation: transcription factors + RNA polymerase bind promoter; Elongation: RNA pol builds mRNA; Termination: RNA pol finishes and releases mRNA.

What does tRNA do?

Anticodon pairs with mRNA codon; tRNA carries the matching amino acid.

What initiates translation and where does it start?

Small ribosomal subunit + initiator tRNA scan mRNA to the start codon AUG.

Summarize elongation in translation.

New tRNA enters A site → peptide bonds form with P site tRNA → ribosome translocates; old tRNA exits E site.

List interphase subphases and what happens.

G₁ growth/decision; S DNA replication; G₂ growth & division prep.

What does semi-conservative DNA replication mean?

Each daughter DNA has one old strand + one new strand.

Match the mitosis phases to the key events: Prophase.

Chromosomes condense; spindle forms; nuclear envelope breaks.

Match the mitosis phases to the key events: Metaphase.

Chromosomes line up at midline.

What promotes vs inhibits cell division?

Promote: nutrients, growth factors, anchorage. Inhibit: high cell density (contact inhibition).