DNA, Translation, Transcription

Nucleotide

The building block of nucleic acids, consisting of a phosphate group, a sugar molecule (deoxyribose in DNA), and a nitrogenous base.

3' prime side and 5' prime side

The ends of a nucleotide, with the prime numbers indicating the position of the carbon atom in the sugar molecule.

Nitrogenous base

A molecule that is attached to the sugar molecule in a nucleotide, such as cytosine, thymine, uracil, adenine, or guanine.

Pyrimidines

Nitrogenous bases with a single, 6-membered ring, including cytosine, thymine, and uracil.

Purines

Nitrogenous bases with a 5-membered ring attached to a 6-membered ring, including adenine and guanine.

Transformation

The phenomenon of a change in genotype and phenotype due to the assimilation of foreign DNA.

DNA polymerase

Enzymes that catalyze the elongation of new DNA strands during replication.

Semiconservative model of replication

The model that predicts each daughter DNA molecule will have one old strand (parent molecule) and one newly made strand.

Primase

An enzyme that starts a short RNA chain (primer) by adding RNA nucleotides one at a time using parental DNA as a template.

Replication fork

A Y-shaped region where new DNA strands are elongating during DNA replication.

Antiparallel

The opposite orientation of the two strands in the DNA double helix.

Central Dogma of Molecular Genetics

The concept that cells are governed by a cellular chain of command, with RNA acting as a bridge between genes and proteins.

Transcription

The synthesis of RNA using DNA information.

Translation

The synthesis of a polypeptide using information in mRNA.

Genetic code

The triplet code that determines the sequence of amino acids in a protein, with codons being read in the 5' to 3' direction.

RNA polymerase

The enzyme that catalyzes the synthesis of RNA by joining together RNA nucleotides that are complementary to the DNA template strand.

RNA synthesis

The process of creating RNA molecules using DNA as a template.

Uracil

A nitrogenous base found in RNA that pairs with adenine.

Thymine

A nitrogenous base found in DNA that pairs with adenine.

DNA polymerase

An enzyme that adds nucleotides to the growing DNA strand.

Primer

A short segment of RNA or DNA that serves as a starting point for DNA synthesis.

Helicase

An enzyme that unwinds the DNA double helix during DNA replication.

RNA Polymerase

An enzyme that synthesizes RNA using DNA as a template.

Transcription

The process of synthesizing RNA from a DNA template.

Promoter

A specific sequence of DNA that signals the start of transcription.

Transcription factors

Proteins that mediate the binding of RNA polymerase to the promoter and initiation of transcription.

Transcription initiation complex

The assembly of transcription factors and RNA polymerase bound to a promoter.

TATA box

A specific promoter sequence that is crucial for the formation of the transcription initiation complex in eukaryotes.

Elongation

The process of adding nucleotides to the growing RNA strand during transcription.

Termination

The process of ending transcription and releasing the RNA transcript.

Terminator

A specific sequence of DNA that signals the end of transcription in bacteria.

Polyadenylation signal

A specific sequence of DNA that signals the end of transcription in eukaryotes.

RNA processing

The modification of RNA molecules after transcription in eukaryotic cells.

Primary transcript

The RNA molecule produced after transcription in eukaryotes.

5' cap

A modified nucleotide added to the 5' end of the primary transcript during RNA processing.

Poly-A tail

A sequence of adenine nucleotides added to the 3' end of the primary transcript during RNA processing.

RNA splicing

The process of removing introns and joining exons in eukaryotic RNA transcripts.

Introns

Noncoding regions of RNA transcripts that are removed during RNA splicing.

Exons

Coding regions of RNA transcripts that are expressed and usually translated into amino acid sequences.

Spliceosome

A complex of proteins and small nuclear ribonucleoproteins (snRNPs) that carries out RNA splicing.

Alternative splicing

The process of including different combinations of exons in the final mRNA molecule, leading to the production of different protein isoforms.

Translation

The process of synthesizing proteins from mRNA using ribosomes.

Messenger RNA (mRNA)

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

Transfer RNA (tRNA)

The RNA molecule that carries amino acids to the ribosome during translation.

Amino acids

The building blocks of proteins.

Aminoacyl-tRNA synthetases

Enzymes that attach the correct amino acid to the corresponding tRNA molecule.

Ribosomes

Complexes of proteins and ribosomal RNA (rRNA) that facilitate protein synthesis.

A site

The ribosomal site where the tRNA carrying the next amino acid to be added to the growing polypeptide chain binds.

P site

The ribosomal site where the tRNA carrying the growing polypeptide chain binds.

E site

The ribosomal site where discharged tRNAs leave the ribosome.

Initiation

The first stage of translation, where the ribosome assembles on the mRNA and the first amino acid is added to the growing polypeptide chain.

Elongation

The second stage of translation, where amino acids are added one by one to the growing polypeptide chain.

Termination

The final stage of translation, where the ribosome reaches a stop codon and the polypeptide chain is released.

Codon

A three-nucleotide sequence on mRNA that codes for a specific amino acid.

Anticodon

A three-nucleotide sequence on tRNA that is complementary to a codon on mRNA.

Wobble

The flexible pairing at the third base of a codon-anticodon pair, allowing some tRNAs to bind to more than one codon.

Translation

The process in which the genetic information in mRNA is used to synthesize a protein.

tRNA

Transfer RNA molecules that carry amino acids to the ribosome during translation.

P site

The site on the ribosome where the tRNA carrying the growing polypeptide chain is located.

E site

The site on the ribosome where the empty tRNA is moved to and released.

A site

The site on the ribosome where the next codon to be translated is brought in by the mRNA.

Termination of Translation

The process of translation ending when a stop codon reaches the A site of the ribosome.

Release factor

A protein that promotes the release of the polypeptide chain from the tRNA in the P site during termination of translation.

Protein Folding

The process in which a polypeptide chain spontaneously coils and folds to form a protein with a specific three-dimensional shape.

Post-Translational Modifications

Modifications that may be required for a protein to become functional after synthesis.

Gene Mutations

Changes in the genetic material of a cell or virus.

Mutagens

Physical or chemical agents that can cause mutations.

Point Mutations

Chemical changes in just one base-pair of a gene.

Nucleotide Substitutions

Point mutations that involve the replacement of one or more nucleotides in a gene.

Frameshift Mutations

Mutations that result from the insertion or deletion of nucleotides, causing a shift in the reading frame of the gene.

Silent Mutation

A substitution mutation that does not change the amino acid produced by a codon due to redundancy in the genetic code.

Missense Mutation

A substitution mutation that still codes for an amino acid, but not the correct amino acid.

Nonsense Mutation

A substitution mutation that changes an amino acid codon into a stop codon, leading to a nonfunctional protein.

Insertions and Deletions

Mutations that involve the addition or loss of a nucleotide in the DNA or mRNA sequence.

One Nucleotide Insertion or Deletion

A frameshift mutation caused by the insertion or deletion of a single nucleotide, resulting in a change in every amino acid past that point.

Alteration of Chromosome Number

Changes in the number of chromosomes, often caused by nondisjunction during meiosis.

Nondisjunction

Failure of homologous chromosomes to separate normally during meiosis.

Aneuploidy

The condition resulting from the fertilization of gametes in which nondisjunction occurred, leading to an abnormal number of chromosomes.

Deletion

A type of chromosomal alteration where a segment within a chromosome is removed.

Inversion

A type of chromosomal alteration where a chromosomal segment is reversed.

Duplication

A type of chromosomal alteration where a segment within a chromosome is repeated.