DNA Replication and Gene Expression

These flashcards cover key concepts related to DNA replication and gene expression processes, including definitions and functions of important terminology.

DNA Replication

The biological process of producing two identical replicas of DNA from one original DNA molecule.

S-phase

The synthesis phase of the cell cycle, during which DNA replication occurs.

Nucleotide

The basic structural unit of DNA and RNA, consisting of a phosphate group, a sugar, and a nitrogenous base.

DNA Polymerase

An enzyme that synthesizes DNA molecules from deoxyribonucleotides.

Template Strand

The strand of DNA used by enzymes to synthesize a new complementary strand.

5' to 3' Direction

The direction in which DNA and RNA are synthesized, with new nucleotides added to the 3' hydroxyl group.

Primer

A short nucleic acid sequence that provides a free 3' hydroxyl group for DNA polymerase to start synthesis.

Complementary Base Pairing

The specific hydrogen bonding between nitrogenous bases in DNA and RNA.

DNA Helicase

An enzyme that unwinds the double helix of DNA at the replication fork.

Leading Strand

The strand that is synthesized continuously in the 5' to 3' direction during DNA replication.

Lagging Strand

The strand that is synthesized discontinuously in short fragments away from the replication fork.

Okazaki Fragment

Short segments of DNA synthesized on the lagging strand during DNA replication.

DNA Ligase

An enzyme that joins the sugar-phosphate backbones of DNA fragments.

Telomere

The repetitive DNA sequences at the ends of chromosomes that protect them.

Telomerase

An enzyme that adds repetitive DNA sequences to the ends of eukaryotic chromosomes.

Topoisomerase

An enzyme that alters the supercoiling of DNA molecules.

Mismatch Repair (MMR)

A DNA repair system that corrects errors made during DNA replication.

Base Excision Repair (BER)

A DNA repair pathway that removes damaged or modified single bases.

Nucleotide Excision Repair (NER)

A versatile DNA repair pathway that removes bulky DNA lesions.

Gene Expression

The process of using information from a gene to synthesize a functional gene product.

Transcription

The process of synthesizing RNA from a DNA template.

Translation

The process of synthesizing a protein from an mRNA template.

RNA Polymerase

An enzyme that synthesizes RNA molecules from a DNA template.

Promoter

A specific DNA sequence that signals the beginning of a gene.

Lac Operon

A cluster of genes in bacteria involved in lactose metabolism.

Operator

A DNA sequence that binds a repressor protein to control transcription.

Repressor Protein

A protein that inhibits gene transcription by binding to the operator.

Transcription Factors

Proteins that control the rate of gene transcription.

Enhancer Sequence

A DNA sequence that can bind activator proteins to increase transcription.

Chromatin

The complex of DNA and proteins that forms chromosomes in eukaryotic cells.

Nucleosome

The basic repeating unit of chromatin, consisting of DNA wound around histone proteins.

Histone Acetylation

The addition of acetyl groups to histone proteins, associated with increased gene expression.

DNA Methylation

The addition of a methyl group to a cytosine base in DNA.

CpG Sequence

A region of DNA where a cytosine is followed by a guanine nucleotide.

DNA Methyltransferase (DNMT)

An enzyme that catalyzes the transfer of a methyl group to DNA.

Nucleoside

A molecule consisting of a nitrogenous base linked to a sugar.

Nucleotide

A nucleoside with one or more phosphate groups attached.

Pyrimidine

A nitrogenous base with a single-ring structure.

Purine

A nitrogenous base with a double-ring structure.

PRPP (Phosphoribosyl Pyrophosphate)

An activated sugar molecule that is a precursor in nucleotide synthesis.

CPS II (Carbamoyl Phosphate Synthetase II)

The enzyme that catalyzes the first committed step in pyrimidine biosynthesis.

OMP (Orotidine Monophosphate)

An intermediate in pyrimidine biosynthesis.

UMP (Uridine Monophosphate)

A pyrimidine nucleotide and precursor for other pyrimidine nucleotides.

THF (Tetrahydrofolate)

A coenzyme essential for the synthesis of purines and thymine.

IMP (Inosine Monophosphate)

The first purine nucleotide to be synthesized.

Ribonucleotide Reductase

An enzyme that catalyzes the reduction of ribonucleotides to deoxyribonucleotides.