Mutations - Terms

triplet expansion

3 base pair repeat is duplicated, sometimes up to thousands of times

Haploid

A cell having one chromosome set or an organism composed of such cells.

Diploid

A cell having two chromosome sets or an individual organism having two chromosome sets in each of its cells.

Oncogene

A gain-of-function mutation that contributes to the production of cancer.

Synonymous Mutation

A mutation hat changes one codon for an amino acid into another codon for that same amino acid. Also called a silent mutation.

Point Mutation

A mutation that alters a single base position in a DNA molecule by converting it to a different base or by by the insert/deletion of a single base in a DNA molecule.

Spontaneous Lesions

DNA dmage occuring in the absence of exposure to mutagens; due primarily to the mutagenic action of the by-products of cellular metabolism

Allele

Different versions of a gene.

Proto-Oncogene

Genes that are normally involved in promoting cell growth. Mutation results in misregulation of the protein such that it signals to the cell to grow (and divide) all the time, even in the absence of growth factors that normally signal the cell to divide. Gain-of-function mutations in one copy of the photo-oncogene can make a cell.

Tumor Suppressor Gene

Genes that normally down-regulate cell division. Loss-of-function mutations in both copies of the gene are required to cause cancer. Genetic predisposition to dance -> an individual inherits one allele from their parents. Therefore, they only need one (more) copy of the gene to acquire a mutation. Knudsen's two-hit hypothesis. Some families will be more likely to produce offspring that will eventually get cancer. EX: RB, p53, BRCA1/2 (indirectly by increasing mutation rates).

Biochemical Mutation

Mutation affects the production of a enzyme involved in the metabolism of an organism.

Silent Mutation

Mutation does not result in any change in the amino acid sequence of the protein. Remember, the genetic code is degenerate.

Somatic Mutation

Mutation in a cell other than the cells that form gametes. Mutation will never be passed on to offspring. Mutation may give rise to a mutant sector if it occurs during development.

Gain of Function Mutation

Mutation results in a protein that has lost some form of regulation or gained some activity over the level of the normal protein. Will often times be dominant over the wild-type allele.

Loss of Function Mutation

Mutation results in production of little-to-no functional protein. Nonsense mutations. Are usually recessive to the WT allele.

Morphological Mutation

Mutation that affects that outward visible properties (size, shape, color) of an organism.

Conditional Mutation

Mutation that results in a phenotype only under certain conditions. Often the condition that is considered in the laboratory in temperate.

Lethal Mutation

Mutation that results in death of an organism.

Nonsense Mutation

Mutation that results in one codon being changed to a stop codon. This new stop codon is called a "premature stop codon". The result of this kind of mutation is shorter protein that is often times nonfunctional.

Germinal Mutation

Mutations in the cells that are destined to development into gametes. Mutation will be passed on to the offspring of organism. Often times an individual will have only one copy of a mutant gene. Therefore, there is a 50% chance that the offspring will inherit the mutant gene since only one set of chromosomes is passed on to the offspring.

Prototrophic

Organisms that are able to synthesize all the biological molecules that they need to survive if given the basic elements. (N, C, P, S)

Auxotrophic

Organisms that can survive ONLY if given nutritional supplements. They are deficient in the enzymes necessary to produce one or more essential biochemical molecules (like amino acids or nucleotides).

Transversion

Purine replaced by a pyrimidine and a pyrimidine replaced by a purine. EX: GC -> TA, GC -> CG

Restrictive Condition

The condition at which the mutation results in mutant phenotype.

Phenotype

The detectable outward manifestation of a specific genotype. EX: Blood type - A, B, AB and O.

Gene

The fundamental physical and functional unit of heredity, which carries information from one generation to the next; a segment of DNA composed of a transcribed region and a regulatory sequence that makes transcription possible.

Wild Type

The reference point for a gene. It will be the version of a gene that occurs in nature of the version found in the standard laboratory stock of an organism. Often abbreviated wt. "normal" "+"

Genotype

The specific composition of a certain gene. Often refers to the entire allelic composition of an organism. Ex: Blood type (Ib, Ib1, Ibi).

apurinic site

a DNA site that has lost a purine residue

Spontaneous Mutation

a mutation occurring in the absence of exposure to mutagens

Depurination

loss of guanine or adenine base from a nucleotide

Missense Mutation

mutation results in one codon being changed to another. At the protein level, there will be one amino aid that is different.

Frameshift Mutation

one base deletion or insertion (indwells). Will result in a change in the reading frame during translation. Amino acid encoded by the codon that had insert.deletion will be incorrect and the rest of the protein sequence will also be incorrect. Shorter protein is usually made as reading frame shift will result in a stop codon being brought into the reading frame.

Transition

purine replaced by apron and a pyrimidine replaced by a pyrimidine. EX: GC -> AT, TA -> CG

deamination

removal of NH2 (amine) and replacement with =O

Permissive Condition

the condition at which the mutation results in no abnormal phenotype.

Tautomers

the same atoms in a molecule but they are arranged in different positions and have different bonding