Cytogenetics: The Central Dogma, DNA Replication, Transcription, and Translation

Vocabulary-style flashcards based on lecture slides detailing Central Dogma mechanisms, enzymes in DNA replication, types of RNA, eukaryotic vs prokaryotic transcription, and translation steps.

DNA Replication

The process by which DNA is essentially doubled within a dividing cell.

Semi-Conservative Method

The method of DNA replication that results in a double-stranded DNA molecule containing one parental strand and one new daughter strand.

Substrates of DNA Replication

The four deoxyribonucleoside triphosphates: dATP, dCTP, dGTP, and dTTP.

DNA B protein (Helicase)

An enzyme that unwinds the complementary double-stranded DNA helix at the replication fork.

Primase

A DNA-dependent RNA polymerase that synthesizes a short RNA primer in a $5'$ to $3'$ direction.

DNA Topoisomerase I & II

Enzymes that relieve torsional strain caused by supercoiling by cutting and rejoining single or double DNA strands.

DNA Polymerase

Enzyme responsible for DNA chain elongation during replication.

DNA Ligase

An enzyme that joins Okazaki fragments by catalyzing the formation of phosphodiester bonds to seal nicks.

DNA A protein

Protein that recognizes and binds to the origin of replication (Ori) and denatures the DNA duplex.

SSB (Single strand binding protein)

Protein that binds separated single-stranded DNA to stabilize it and prevent re-association.

Ter binding protein

Protein that binds termination sequences to prevent helicase from further unwinding DNA and facilitate termination.

Proofreading Activity

The $3'$ to $5'$ exonuclease activity possessed by DNA polymerases to remove incorrect bases during synthesis.

DNA Polymerase I (Prokaryotic)

Prokaryotic enzyme involved in gap filling and RNA primer removal/synthesis between Okazaki fragments on the lagging strand.

DNA Polymerase II (Prokaryotic)

Prokaryotic polymerase primarily involved in DNA proofreading and DNA repair.

DNA Polymerase III (Prokaryotic)

The main prokaryotic enzyme responsible for leading and lagging strand DNA synthesis.

DNA Polymerase $\alpha$ (Eukaryotic)

Eukaryotic polymerase responsible for gap filling and synthesis between Okazaki fragments of the lagging strand.

DNA Polymerase $\beta$ (Eukaryotic)

Eukaryotic DNA polymerase specifically dedicated to DNA repair.

DNA Polymerase $\gamma$ (Eukaryotic)

Eukaryotic DNA polymerase responsible for mitochondrial DNA synthesis.

DNA Polymerase $\delta$ (Eukaryotic)

Eukaryotic enzyme responsible for synthesis of leading and lagging strands.

DNA Polymerase $\epsilon$ (Eukaryotic)

Eukaryotic enzyme responsible for DNA proofreading and DNA repair.

Primosome

A complex formed by the enzyme primase in association with SSB proteins that produces RNA primers.

Leading Strand

The DNA chain running $3' \rightarrow 5'$ that is copied continuously by DNA polymerase III in the $5' \rightarrow 3'$ direction toward the replication fork.

Lagging Strand

The DNA chain running $5' \rightarrow 3'$ that is copied discontinuously away from the replication fork, requiring multiple RNA primers.

Okazaki Fragments

Short, newly synthesized DNA fragments formed on the lagging template strand during DNA replication.

Prokaryotic Topoisomerase Inhibitors

Antibiotic drugs including Novobiocin, Nalidixic acid, and Ciprofloxacin that inhibit prokaryotic DNA gyrase to treat infections.

Human Topoisomerase Inhibitors

Anticancer drugs such as Camptothecin, Adriamycin, Etoposide, and Doxorubicin that inhibit human topoisomerase.

Heterochromatin

Highly condensed, tightly packed, transcriptionally inactive chromatin rich in repetitive DNA sequences.

Euchromatin

Less condensed, relaxed, transcriptionally active chromatin rich in protein-coding genes.

Transcription

The synthesis of a single-stranded RNA (mRNA) molecule from a double-stranded DNA template strand in a $5'$ to $3'$ direction.

mRNA (messenger RNA)

RNA type that carries genetic code from DNA in triplets of nucleotides (codons) to serve as a template for protein synthesis.

rRNA (ribosomal RNA)

RNA type that combines with proteins and enzymes in the cytoplasm to form ribosomes.

tRNA (transfer RNA)

Adapter RNA molecules that carry specific amino acids and read the genetic code on mRNA during translation.

Sense Strand

The non-template DNA strand ($5' \rightarrow 3'$) that shares the same base sequence as mRNA (with thymine instead of uracil) and acts as the plan to make a protein.

Antisense Strand

The template DNA strand ($3' \rightarrow 5'$) read by RNA polymerase to synthesize complementary mRNA.

Promoter Region

A specific sequence of DNA where RNA polymerase binds to initiate transcription, requiring a sigma factor in prokaryotes.

Introns

Non-coding sections of nucleic acids located between coding regions that are excised from pre-mRNA during splicing.

Exons

Coding regions of nucleic acids that remain after splicing to form mature mRNA.

5' Cap

A modified guanine molecule added to the 5' end of pre-mRNA during RNA processing.

Poly-A Tail

A sequence of multiple adenines added to the 3' end of pre-mRNA during processing.

Translation

The process of decoding mRNA sequences within ribosomes to synthesize polypeptides (proteins).

A-site (Acceptor Site)

The ribosomal binding site where incoming aminoacyl-tRNA molecules bind during translation elongation.

P-site (Donor Site)

The ribosomal binding site that holds the tRNA attached to the growing polypeptide chain.

Start Codon

The codon AUG on mRNA that signals the start of protein translation and codes for methionine.

Stop Codons

Nucleotide triplets (UAA, UAG, UGA) that bind release factors and signal the termination of translation.