Flashcards for Exam

Key terms and definitions for exam review.

Origin of replication

Where DNA replication starts on the chromosome.

Prokaryote

Cell without a nucleus; has one origin of replication.

Eukaryote

Cell with a nucleus; has many origins of replication.

Lagging strand

DNA strand made in short pieces (Okazaki fragments).

Okazaki fragments

Short DNA pieces made on the lagging strand.

Primase

Enzyme that makes a short RNA primer to start DNA synthesis.

DNA Polymerase I

Removes RNA primers and fills in DNA on lagging strand.

DNA Polymerase III

Main enzyme for making new DNA in prokaryotes.

Ligase

Enzyme that joins DNA fragments together.

Single-stranded binding proteins (SSB)

Keep DNA strands apart during replication.

Topoisomerase

Enzyme that relieves twisting in DNA.

Telomerase

Enzyme that adds DNA to chromosome ends in eukaryotes.

Sliding clamp

Protein that helps DNA polymerase stay attached to DNA.

Base excision repair (BER)

Fixes small DNA damage by removing a single base.

DNA glycosylase

Enzyme that removes damaged bases in BER.

AP site

Place in DNA missing a base (after glycosylase action).

Nucleotide excision repair (NER)

Removes bulky DNA damage.

Mismatch repair

Fixes mistakes made during DNA replication.

MutL/MutH

Proteins involved in mismatch repair.

Direct repair

Fixes DNA damage directly, without removing bases.

Homologous recombination

Repairs DNA breaks using a similar DNA molecule.

Holliday junction

Four-stranded DNA structure formed during recombination.

Transcription

Making RNA from a DNA template.

Promoter

DNA sequence where RNA polymerase binds to start transcription.

TATA box

DNA sequence in eukaryotic promoters, helps start transcription.

Sigma factor

Protein in prokaryotes that helps RNA polymerase find the promoter.

RNA polymerase

Enzyme that makes RNA from DNA.

snRNPs

Help remove introns from RNA.

Spliceosome

Complex that removes introns from pre-mRNA.

5' cap

Modified G nucleotide added to the front of eukaryotic mRNA for stability.

Poly-A tail

Stretch of A nucleotides added to the end of eukaryotic mRNA for stability.

Enhancer

DNA sequence that increases gene expression, can be far from the gene.

Translation

Making protein from mRNA.

Ribosome

Molecular machine that makes proteins.

tRNA

Transfer RNA; brings amino acids to the ribosome.

Aminoacyl-tRNA synthetase

Enzyme that attaches amino acids to tRNA.

Codon

Three-base sequence in mRNA that codes for an amino acid.

Anticodon

Three-base sequence in tRNA that pairs with mRNA codon.

Start codon

First codon in mRNA (usually AUG, codes for methionine).

Stop codon

Codon that signals the end of translation (UAA, UAG, UGA).

Shine-Dalgarno sequence

Sequence in prokaryotic mRNA that helps ribosome find the start codon.

EF-G

Protein that helps move the ribosome along mRNA during translation.

Lac operon

Group of genes in bacteria for lactose metabolism.

Catabolite repression

When glucose prevents the lac operon from being active.

Trp operon

Group of genes for tryptophan synthesis.

Attenuation

Stops transcription early if enough tryptophan is present.

Chromatin remodeling

Changing how tightly DNA is wrapped around histones.

Histone acetylation

Adding acetyl groups to histones to loosen DNA.

Point mutation

Change in a single DNA base.

Nonsense mutation

Mutation that changes a codon to a stop codon.

Frameshift mutation

Insertion or deletion that changes the reading frame of a gene.

Signal sequence

Peptide that directs a protein to a specific location.

Sickle-cell mutation

Point mutation that changes glutamate to valine.