Gene Mutation, Transposable Elements and DNA Repair Flashcards
Mutation
Heritable change in genetic information.
Somatic Mutation
Mutation that arises in somatic cells and does not give rise to gametes.
Germ Line Mutation
Mutation in a germ-line cell (one that gives rise to gametes).
Gene Mutation
Mutation that affects a single gene or locus.
Base Substitution
Mutation in which a single pair of bases in DNA is altered.
Frameshift Mutation
Mutation that alters the reading frame of a gene.
Transversion
Base substitution in which a purine is replaced by a pyrimidine, or a pyrimidine is replaced by a purine.
Transition
Base substitution in which a purine is replaced by a different purine, or a pyrimidine is replaced by a different pyrimidine.
Insertion
Mutation in which one or more nucleotide pairs are added to a DNA sequence.
Deletion
Mutation in which one or more nucleotides are deleted from a DNA sequence.
Reverse Mutation (Reversion)
Mutation that changes a mutant phenotype back into the wild type.
In Frame Insertion
Insertion of some multiple of three nucleotides that do not alter the reading frame of the gene.
Forward Mutation
Mutation that alters a wild-type phenotype.
Expanding Nucleotide Repeat
Type of mutation in which the number of copies of a set of nucleotides (most often three nucleotides) increases in succeeding generations.
Neutral Mutation
Mutation that changes the amino acid sequence of a protein but does not alter the function of the protein.
Nonsense Mutation
Mutation that changes a sense codon (one that specifies an amino acid) into a stop codon (one that terminates translation).
Loss Of Function Mutation
Mutation that causes the complete or partial absence of normal function.
Silent Mutation
Change in the nucleotide sequence of DNA that does not alter the amino acid sequence of a protein.
Gain Of Function Mutation
Mutation that causes the cell to produce a protein or gene product whose function is not normally present; the result could be an entirely new gene product or one produced in an inappropriate tissue or at an inappropriate time in development.
Spontaneous Mutation
Mutation that arises from natural changes in DNA structure or from errors in replication.
Lethal Mutation
Mutation that causes premature death.
Mutation Rate
Frequency with which a wild-type allele changes to a mutant allele; generally expressed as the number of mutations per biological unit (i.e., mutations per cell division, per gamete, or per round of replication).
Incorporated Error
Incorporation of a damaged nucleotide or mismatched base pair into a DNA molecule.
Induced Mutation
Mutation that results from environmental agents, such as chemicals or radiation.
Unequal Crossing Over
Misalignment of the two DNA molecules during crossing over, resulting in one DNA molecule with an insertion and the other with a deletion.
Strand Slippage
Slipping of the template and newly synthesized strands in replication in which one of the strands loops out from the other and nucleotides are inserted or deleted on the newly synthesized strand.
Deamination
Loss of an amino group NH2 from a base.
Depurination
Break in the covalent bond connecting a purine base to the 1’-carbon atom of deoxyribose sugar, resulting in the loss of the purine base.
Replicated Error
An incorporated error that is replicated, leading to a permanent mutation.
Intercalating Agent
Molecule that is the approximately same size as a nucleotide and may become sandwiched between adjacent bases in DNA, distorting the three-dimensional structure of the DNA helix and causing single-nucleotide insertions and deletions in replication.
Pyrimidine Dimer
Structure in which a bond forms between two adjacent pyrimidine molecules on the same strand of DNA; distorts the normal configuration of the DNA molecule and often blocks replication.
Mutagen
Any environmental agent that significantly increases the rate of mutation above the spontaneous rate.
Alkylating Agents
A chemical that can add a methyl (CH3) group to a nucleotide.
Base Analog
Chemical substance that has a structure similar to that of one of the four standard nitrogenous bases of DNA and may be incorporated into newly synthesized DNA molecules in replication.
Terminal Inverted Repeat
Sequences found at both ends of a transposable element that are inverted complements of one another.
Transposition
Movement of a transposable element from one location to another.
Ames Test
Test in which special strains of bacteria are used to evaluate the potential of chemicals to cause cancer.
Flanking Direct Repeat
Short, directly repeated sequence produced on either side of a transposable element when the element inserts into DNA.
Transposable Element
DNA sequence capable of moving from one site to another within the genome through a mechanism that differs from that of homologous recombination.
DNA Transposon
Transposable element that transposes as DNA.
retrotransposon
Type of transposable element in eukaryotic cells that possesses some characteristics of retroviruses and transposes through an RNA intermediate.
SOS system
System of proteins and enzymes that allows a cell to replicate its DNA in the presence of a distortion in DNA structure; makes numerous mistakes in replication and increases the rate of mutation.
Mistmatch Repair
Process that corrects mismatched nucleotides in DNA after replication has been completed. Enzymes excise incorrectly paired nucleotides from the newly synthesized strand and use the original nucleotide strand as a template for replacing them.
Direct repair
DNA repair in which modified bases are changed back into their original structures.
base-excision repair
DNA repair that first excises modified bases and then replaces the entire nucleotide.
nucleotide-excision repair
DNA repair that removes bulky DNA lesions and other types of DNA damage.
