Bio - 102 - DNA / Mutations

DNA

a double-stranded molecule consisting of two spirally wound polymers of nucleotides that store genetic information, including the information needed to synthesize proteins. Each nucleotide in this molecule is composed of the sugar deoxyribose, a phosphate group, and one of four nitrogenous bases: adenine, cytosine, guanine, or thymine.

Replication

the biological process where a double-stranded DNA molecule is copied to produce two identical DNA molecules

Transcription

the biological process where the genetic information stored in a DNA segment is copied into a messenger RNA (mRNA) molecule

Translation

the second step in gene expression where ribosomes read the genetic instructions from a messenger RNA (mRNA) molecule and use that information to assemble a specific sequence of amino acids, forming a protein

Gene

The smallest unit of DNA that governs a genetic characteristic and contains the code for the synthesis of a protein or an RNA molecule. They are located on chromosomes.

Gene Expression

The creation of a functional product, such as a specific protein or RNA, using the coding information stored in a gene. This expression is the means by which a gene influences the cell or organism in which it is found.

Anti-codon

A sequence of three nitrogenous bases on a transfer RNA molecule that enables it to form complementary base pairs with a corresponding codon on an mRNA molecule.

Codon

A sequence of three nitrogenous bases in an mRNA molecule. Each codon specifies either a particular amino acid or a signal to start or stop the translation of a protein.

Genetic Code

the set of rules by which a cell translates information encoded in genetic material (DNA or RNA) into proteins, using three-letter nucleotide sequences called codons

Elongation

The second of three stages of gene transcription (in which RNA polymerase synthesizes the complete RNA from free nucleotides) or translation (in which the ribosomes read the message in the mRNA to produce a complete chain of amino acids).

Intiation

The first of the three main stages of gene transcription (in which RNA polymerase begins transcribing the template strand of DNA) or translation (in which the ribosome- tRNA complex detects the start codon in an mRNA molecule and protein synthesis begins)

Termination

The third of three stages of gene transcription (in which RNA polymerase reaches the terminator sequence of bases) or translation (in which the ribosome reaches the stop codon).

Exon

A DNA sequence within a gene that encodes part of a protein. Each exon codes for a stretch of amino acids.

Intron

A DNA sequence within a gene that does not specify part of the gene’s final protein or RNA product. Enzymes in the nucleus must remove introns from mRNA, tRNA, and rRNA molecules for these molecules to function properly.

Mutagen

A substance or energy source that alters DNA.

Mutation

A change in the sequence of an organ- ism’s DNA. Because new alleles arise only by mutation, mutations are the original source of all genetic variation.

Ribosome

A minute organelle composed of proteins and RNA at which new proteins are synthesized. Ribosomes can be either attached to the endoplasmic reticulum or free in the cytosol.

Semiconservative replication

DNA replication in which one “old” (template) strand is retained, or conserved, in each new helix.

DNA polymerase

The key enzyme that cells use to replicate their DNA. In DNA technology, DNA polymerase is used in the polymerase chain reaction to make many copies of a gene or other DNA sequence.

RNA polymerase

The key enzyme in DNA transcription. RNA polymerase links together the nucleotides of the RNA molecule specified by a gene.

helicase

an essential enzyme that uses the energy from ATP hydrolysis to unwind and separate double-stranded nucleic acids (DNA or RNA) into single strands.

Ligase

an enzyme which brings about ligation of DNA or another substance.

start codon

A three-nucleotide sequence on an mRNA molecule (usually the codon AUG) that signals where translation should begin.

stop codon

A three-nucleotide sequence on an mRNA molecule that signals where translation should end.

template strand

In gene transcription, the strand of DNA (of the two strands in a DNA molecule) that is copied into RNA and is therefore complementary to the RNA synthesized from it.

transfer RNA (tRNA)

A type of RNA that transfers the amino acid specified by mRNA to the ribosome during protein synthesis.

messenger RNA (mRNA)

A type of RNA that specifies the order of amino acids in a protein.

Ribosomal RNA (rRNA)

A type of RNA that is an important component of ribosomes.