DNA Structure, Replication, and Gene Expression

Griffith's experiment

Demonstrated bacterial transformation via hereditary material.

Transforming Principle

Molecule responsible for cell programming, debated identity.

Hershey-Chase experiment

Proved DNA, not protein, is hereditary material.

DNA

Nucleic acid governing heredity in cells.

Double helix

DNA structure consisting of two intertwined strands.

Sugar-phosphate backbone

Structural framework of DNA, supports nitrogenous bases.

Nitrogenous base pairs

Adenine pairs with Thymine; Cytosine pairs with Guanine.

Nucleotide

Building block of DNA, consists of sugar, phosphate, base.

Antiparallel strands

DNA strands run in opposite directions (5' to 3').

5' end

One end of DNA strand, phosphate group attached.

3' end

Other end of DNA strand, hydroxyl group attached.

S phase

Phase of interphase when DNA replication occurs.

Semiconservative replication

Each new DNA molecule contains one original strand.

Meselson-Stahl experiment

Confirmed semiconservative nature of DNA replication.

Helicases

Enzymes that unwind and separate DNA strands.

Replication origin

Specific DNA sequence where replication begins.

DNA template

Strand serving as a guide for complementary strand synthesis.

Complementary strand

Newly synthesized DNA strand matching the template strand.

Hydrogen bonds

Weak bonds between nitrogenous base pairs in DNA.

Cellular DNA

Identical in all body cells except gametes.

Protein synthesis

Process influenced by the expression of DNA.

Genome replication

Copying entire DNA content for new cell formation.

Replication Fork

Y-shaped area where DNA splits during replication.

Replication Bubble

Unwound region of DNA during replication.

Template Strands

Single unwound DNA strands used for replication.

Primase

Enzyme that synthesizes primer for DNA replication.

DNA Polymerase III

Adds nucleotides in 5' to 3' direction.

DNA Polymerase I

Removes primer sequences after replication completion.

Leading Strand

Continuously replicated DNA strand during elongation.

Lagging Strand

Replicated in short segments called Okazaki fragments.

Okazaki Fragments

Short DNA segments on the lagging strand.

DNA Ligase

Enzyme that splices Okazaki fragments together.

Termination

Dismantling of replication complex after DNA replication.

Helicase

Enzyme that unwinds and cleaves DNA strands.

Transcription

Process of copying DNA into mRNA.

mRNA

Messenger RNA that carries genetic information.

RNA Polymerase

Enzyme that synthesizes mRNA from DNA template.

Promoter Region

DNA sequence where RNA polymerase binds to initiate transcription.

Introns

Non-coding sequences removed from mRNA before translation.

Exons

Coding sequences that remain in mRNA after splicing.

Central Dogma

Flow of genetic information: DNA to mRNA to protein.

Codons

Three-nucleotide sequences on mRNA coding for amino acids.

Anticodons

Three-nucleotide sequences on tRNA complementary to codons.

Gene Expression

Process by which genes are transcribed and translated.

mRNA

Carries genetic info from DNA to ribosomes.

Introns

Non-coding RNA sequences removed before translation.

Exons

Coding RNA sequences that remain after intron removal.

Eukaryotes

Organisms where mRNA intron removal occurs.

Codons

Groups of three mRNA bases coding for amino acids.

tRNA

Transfer RNA linking codons to specific amino acids.

Anticodons

tRNA sequences complementary to mRNA codons.

Ribosomes

Cell structures that synthesize proteins from mRNA.

rRNA

Ribosomal RNA forming the core of ribosomes.

Polypeptide chain

A sequence of amino acids linked together.

A site

Ribosome site where new tRNA enters.

P site

Ribosome site where amino acids are added.

E site

Ribosome site where tRNA exits after transfer.

Bound ribosomes

Produce proteins for export outside the cell.

Free ribosomes

Produce proteins for use within the cell.

Transcription

Process of converting DNA into mRNA.

Translation

Process of synthesizing proteins from mRNA.

Mutation

Mistakes in genetic coding during replication or translation.

Point mutation

Single base change in DNA sequence.

Frameshift mutation

Insertion or deletion altering reading frame.

Silent mutation

No change in amino acid sequence.

Missense mutation

Change in one amino acid in the sequence.

Nonsense mutation

Creates a premature stop codon in translation.

Somatic Mutation

Mutations in body cells, not inherited.

Germ Line Mutation

Mutations in reproductive cells, inherited by offspring.

Point Mutation

Chemical change affecting one or few nucleotides.

Nucleotide Substitution

Replacement of one nucleotide with another.

Frameshift Mutation

Insertion or deletion altering the entire reading frame.

Silent Mutation

No effect on overall cell functioning.

Missense Mutation

Produces slightly altered but functional polypeptide.

Nonsense Mutation

Gene unable to code for functional polypeptide.

Mitochondrial DNA (mtDNA)

DNA inherited only from the mother.

Recombinant DNA

DNA containing genetic material from different sources.

Genetic Engineering

Modifying organisms to express desirable traits.

Restriction Endonucleases

Enzymes cutting DNA at specific recognition sites.

DNA Ligase

Enzyme that joins DNA fragments together.

Plasmids

Circular DNA segments in bacteria containing genetic info.

Gel Electrophoresis

Technique to analyze and compare DNA fragments.

Negative Charge of DNA

Causes DNA to migrate towards positive electrode.

Taq Polymerase

Enzyme used in PCR for DNA amplification.

Polymerase Chain Reaction (PCR)

Method to amplify specific DNA sequences.

Genetically Modified Organisms (GMO)

Organisms with traits not achievable through breeding.

Common Ancestor

An ancestor shared by different species.

Banding Pattern

Visual representation of DNA fragments in gel.

DNA Fragmentation

Cutting DNA into smaller pieces for analysis.