chapter 9 bio pt. 2

What is the purpose of DNA replication?

To ensure daughter cells receive an identical copy of the genome.

What rule allows DNA to serve as a template for new DNA strands?

Complementary base pairing (A↔T, G↔C).

What model describes DNA replication?

Semiconservative replication (one old + one new strand).

What are the three basic steps of eukaryotic DNA replication?

initiation, elongation, termination.

List the major enzymes in DNA replication.

Helicase, RNA primase, DNA polymerase, DNA ligase.

What is the difference between the leading and lagging strands?

Leading strand is continuous; lagging strand is synthesized in short fragments.

Why are Okazaki fragments made?

DNA polymerase can only build 5'→3', so lagging strand is discontinuous.

What protects chromosome ends?

Telomerase adds repeated sequences (TTAGGG in humans).

What repairs DNA replication errors?

DNA polymerase proofreading & mismatch repair.

What is the central dogma of genetics?

DNA → RNA → Protein. 

What enzyme synthesizes mRNA from DNA?

RNA polymerase. 

What are the three stages of transcription?

Initiation, elongation, termination. 

What is a promoter?

DNA sequence signaling gene start.

What is splicing?

Removing introns and joining exons.

What is added to mRNA before it leaves the nucleus?

5’ cap & 3’ poly-A tail

Where does translation occur?

Ribosome.

What molecule brings amino acids to the ribosome?

tRNA

What are the three ribosome sites?

A (acceptor), P (peptidyl), E (exit). (“APE”)

What is the first amino acid in most proteins?

Methionine (AUG start codon).

What enzyme charges tRNA with amino acids?

Aminoacyl-tRNA synthetase.

How do prokaryotes regulate genes?

Mostly at transcription level.

What is the lac operon?

Inducible operon that turns on in presence of lactose.

What happens when lactose is absent in the lac operon?

Repressor binds operator → operon OFF.

What is alternative splicing?

Different exon combinations create multiple proteins from one gene.