AP Bio Unit 6 Studyguide

Origin of replication

Specific sites where DNA replication begins.

Helicase

An enzyme that unwinds and separates double-stranded DNA by breaking hydrogen bonds.

Replication fork

The structure formed when DNA is unwound during replication.

Single-strand binding proteins (SSBs)

Proteins that bind to separated DNA strands to prevent them from reannealing.

Topoisomerase

An enzyme that prevents supercoiling in DNA ahead of the replication fork.

DNA polymerase

An enzyme that adds nucleotides to the growing DNA strand.

Leading Strand

The DNA strand synthesized continuously in the 5' to 3' direction toward the replication fork.

Lagging Strand

The DNA strand synthesized discontinuously in short segments called Okazaki fragments.

DNA ligase

An enzyme that joins Okazaki fragments on the lagging strand.

Somatic mutations

Mutations that occur in body cells and cannot be passed on to offspring.

Germline mutations

Mutations that occur in gametes and can be passed on to offspring.

Gene mutations

Mutations that affect a single gene by altering its nucleotide sequence.

Chromosomal mutations

Mutations that affect large sections of chromosomes or entire chromosomes.

Silent mutation

A nucleotide change that does not alter the amino acid sequence due to the redundancy in the genetic code.

Missense mutation

A single nucleotide change that alters the amino acid sequence of a protein.

Nonsense mutation

A mutation that creates a premature stop codon, leading to a truncated protein.

Spontaneous mutations

Mutations that occur naturally due to errors in DNA replication or repair.

Induced mutations

Mutations caused by external factors such as radiation or chemicals.

Messenger RNA (mRNA)

RNA that carries genetic information from DNA to ribosomes for protein synthesis.

Transfer RNA (tRNA)

RNA that delivers amino acids to ribosomes during protein synthesis.

Small nuclear RNA (snRNA)

RNA involved in RNA processing, specifically splicing of pre-mRNA.

RNA polymerase

The enzyme that synthesizes RNA by adding ribonucleotides during transcription.

Activation of the lac operon

Occurs when lactose binds to the repressor, allowing transcription of genes for lactose metabolism.

Repression of the trp operon

Occurs when tryptophan binds to the repressor, blocking transcription of genes needed for tryptophan synthesis.

Euchromatin

Loosely packed chromatin that is accessible for transcription.

Heterochromatin

Tightly packed chromatin that is generally transcriptionally inactive.

Histone acetylation

The addition of acetyl groups to histones, which loosens DNA and promotes transcription.

DNA methylation

The addition of methyl groups to DNA, which typically silences gene expression.

MicroRNA (miRNA)

Small RNA molecules that can regulate gene expression by blocking translation or promoting degradation of mRNA.

Post-translational modifications (PTMs)

Modifications made to proteins after translation, such as phosphorylation and glycosylation.