DNA structure and Replication

alternative RNA splicing

A process that allows a single gene to code for multiple proteins.

codon

A sequence of three nucleotides on an mRNA molecule that codes for a specific amino acid.

deoxyribose

The five-carbon sugar found in DNA nucleotides.

DNA ligase

An enzyme that joins DNA fragments together.

DNA polymerase

An enzyme that synthesizes new DNA strands during replication.

double helix

The twisted, ladder-like structure of DNA.

epigenetic

The study of changes in gene expression that are not caused by changes in the DNA sequence itself.

exon

A segment of a gene that codes for a protein.

gene expression

The process by which a gene's information is used to synthesize a functional product, like a protein.

genetic code

The set of rules by which information encoded in DNA or RNA is translated into proteins.

helicase

An enzyme that unwinds the DNA double helix during replication.

intron

A non–protein-coding intervening sequence that is spliced from mRNA during processing.

lagging strand

The DNA strand that is replicated discontinuously in short fragments.

leading strand

The DNA strand that is replicated continuously in the 5' to 3' direction.

mismatch repair

A cellular process that corrects errors in DNA replication.

mRNA

Messenger RNA; a molecule that carries the genetic code from DNA to the ribosome for protein synthesis.

mutation

A change in the DNA sequence.

nitrogenous base

A nitrogen-containing molecule that is a component of nucleotides.

nontemplate strand

The DNA strand that is not used as a template for transcription.

nucleotide excision repair

A DNA repair mechanism that removes damaged nucleotides.

Okazaki fragments

Short, newly synthesized DNA fragments on the lagging strand.

phosphate group

A functional group that is a component of nucleotides.

post-transcriptional

Referring to events that occur after transcription, such as RNA processing.

post-translational

Referring to events that occur after translation, such as protein folding and modification.

primer

A short strand of RNA that provides a starting point for DNA replication.

promoter

A sequence of DNA where transcription begins.

replication fork

The Y-shaped region where DNA is unwound during replication.

RNA polymerase

An enzyme that synthesizes RNA from a DNA template.

rRNA

Ribosomal RNA; a component of ribosomes.

semiconservative replication

The process of DNA replication in which each new DNA molecule consists of one original strand and one new strand.

splicing

The process of removing introns from pre-mRNA.

start codon

A three-nucleotide sequence that signals the beginning of translation.

stop codon

A three-nucleotide sequence that signals the end of translation.

telomerase

An enzyme that adds DNA to the ends of chromosomes.

telomere

A repetitive DNA sequence at the end of a chromosome that protects it from degradation.

template strand

The DNA strand that is used as a template for transcription.

transcription bubble

The region of DNA that is unwound and open during transcription.

tRNA

Transfer RNA; a molecule that brings amino acids to the ribosome during translation.