AP Biology - Unit 6: Gene Expression & Regulation

sonnnnnnn (prolly hardest unit, study!!)

DNA

Deoxyribonucleic acid - Nucleic acid that is responsible for carrying genetic information in a cell. It is double stranded and contains the sugar deoxyribose, and uses nitrogenous bases to code genetic info.

RNA

Ribonucleic acid - Single-stranded nucleic acid involved in protein synthesis, containing the sugar ribose and using the nitrogenous bases adenine, cytosine, guanine, and uracil.

Nucleus

Organelle in eukaryotic cells that stores DNA

Nucleoid

Looped central chromosome in prokaryotic cells that is not membrane bound or circular,

DNA replication is _____

Semiconservative - New strands of DNA are composed of one conserved strand and one newly synthesized strand

Mutation

A permanent change in the nucleotide sequence of DNA that can alter a gene or its expression.

Frameshift mutation

A mutation caused by the insertion or deletion of nucleotides that shifts the reading frame of a gene, altering all downstream codons.

Substitution mutation

A mutation where one nucleotide is replaced by another in a DNA sequence, which may change a codon and alter the amino acid in the protein.

Deletion mutation

A mutation in which one or more nucleotides are removed from a DNA sequence, which can cause a frameshift if the number deleted is not a multiple of three.

Plasmid

A small, circular piece of DNA separate from the bacterial chromosome that can replicate independently and often carries extra genes.

Histone

Protein that DNA wraps around to form nucleosomes, helping package and organize DNA in eukaryotic cells.

Helicase

An enzyme that unwinds the DNA double helix by breaking hydrogen bonds between base pairs, allowing replication or transcription to occur.

Origin of replication

A specific DNA sequence where replication begins, and helicase first unwinds the DNA.

Replication Fork

The Y-shaped region where the DNA double helix is separated into two single strands for replication.

DNA Synthesis is in the ____ Direction

5’ → 3’ direction:
New nucleotides are added to the 3’ end of the growing strand, so synthesis always proceeds from 5’ to 3’.

5’ end

End of DNA/RNA with a free phosphate group. DNA is NOT synthesized towards this end

3’ end

End of DNA/RNA with a free Hydroxyl (-OH) group. DNA is synthesized towards this end

Leading strand

The DNA strand that is synthesized continuously toward the replication fork, following the unwinding of the template.

Lagging strand

The DNA strand that is synthesized discontinuously away from the replication fork in short Okazaki fragments, later joined by DNA ligase.

RNA Primer

A short RNA sequence laid down by primase that provides a 3’-OH for DNA polymerase to start DNA synthesis.

Primase

An enzyme that synthesizes a short RNA primer to give DNA polymerase a starting point for replication.

SSB Proteins (Single-strand binding)

Proteins that bind to separated DNA strands during replication to prevent them from reannealing or forming secondary structures.

Okazaki fragments

Short DNA segments synthesized on the lagging strand during DNA replication that are later joined by DNA ligase.

Ligase

Enzyme that joins Okazaki fragments by sealing gaps in the DNA backbone during replication.

Continuous DNA strands are synthesized _____ the replication fork

towards

DNA Pol I

Enzyme that removes RNA primers and replaces them with DNA

Gene

A segment of DNA that codes for a functional product, usually a protein.

mRNA

RNA molecule that carries genetic information from DNA to the ribosome for protein synthesis.

rRNA

RNA that forms the core of the ribosome and helps catalyze protein synthesis.

tRNA

RNA that carries specific amino acids to the ribosome and matches its anticodon to mRNA codons during translation.

Small RNAs

Short RNA molecules that regulate gene expression or protect the genome, including siRNA and miRNA.

Transcription

Process where DNA is copied into RNA by RNA polymerase.

Promoter

DNA sequence where RNA polymerase binds to start transcription.

RNA Polymerase reads DNA in the ____ direction

3’ to 5’

RNA Is synthesized in the ____ direction

5’ to 3’

Terminator

Sequence of a gene that causes RNA Polymerase to dissociate, ending transcription

Template strand

Strand of DNA that serves as a guide for RNA Synthesis during transcription

Template strand is also called:

antisense strand and noncoding strand

RNA is made to mimic the

non-template strand

Coding strand

DNA strand identical in sequence to the RNA transcript (except T in DNA is U in RNA); not used as the direct template.

Polysomes

Clusters of ribosomes simultaneously translating the same mRNA to make multiple copies of a protein.

Codon

Group of 3 nitrogenous bases that codes for an amino acid