Chapter 9.2 – Gene Expression, Transcription, & Translation

What is gene expression?

The process by which a gene’s DNA sequence is used to make a functional product like a protein or RNA.

What is the Central Dogma of molecular biology?

The flow of genetic information: DNA → RNA → Protein.

What are the 3 steps in the Central Dogma?

DNA replication, transcription, and translation.

What is transcription?

The process of copying DNA to make RNA.

What is translation?

The process of using mRNA to build a protein.

Where does transcription occur?

In the nucleus.

Where does translation occur?

On ribosomes in the cytoplasm.

What enzyme carries out transcription?

RNA polymerase.

What are the base pair rules for RNA?

A pairs with U, C pairs with G.

What is mRNA?

Messenger RNA; carries genetic instructions from DNA to ribosome.

What is tRNA?

Transfer RNA; brings amino acids to the ribosome and matches mRNA codons using anticodons.

What is rRNA?

Ribosomal RNA; makes up the ribosome, which assembles proteins.

What is a codon?

A group of 3 mRNA bases that code for 1 amino acid.

What is an anticodon?

3 bases on tRNA that are complementary to a codon on mRNA.

What is a start codon?

AUG; it signals the beginning of translation.

What are stop codons?

UAG, UAA, UGA; signal the end of protein synthesis.

What are introns?

Non-coding segments of RNA removed during splicing.

What are exons?

Coding regions of RNA kept during splicing.

What is a 5' cap?

A protective structure added to the beginning of mRNA.

What is a poly-A tail?

A string of adenines added to the end of mRNA to protect it.

What is splicing?

Editing RNA to remove introns and join exons.

What is an amino acid?

Monomer of a protein; 1 codon = 1 amino acid.

What is a peptide bond?

The bond that links amino acids together.

What is a polypeptide?

A long chain of amino acids; a protein.

What is protein synthesis?

The process of building a protein using transcription and translation.

What are the steps of translation?

Initiation, Elongation, Termination.

What is a frameshift mutation?

An insertion or deletion that shifts the codon reading frame.

What is a silent mutation?

A substitution that does not change the amino acid.

What is a missense mutation?

A substitution that changes one amino acid.

What is a nonsense mutation?

A substitution that creates a stop codon, ending translation early.

Why does RNA use uracil instead of thymine?

U is used in RNA instead of T to distinguish RNA from DNA.

Why convert DNA to RNA?

To protect DNA, regulate gene use, and make many proteins efficiently.

What is the role of RNA polymerase?

It builds the RNA strand during transcription.

What does the ribosome do?

It reads mRNA and assembles amino acids into a protein.

What is the reading frame?

The way mRNA is divided into codons; must start at the correct AUG.

Why are frameshifts dangerous?

They change all downstream amino acids and can ruin the protein.