BIOL 300: Genes Can Be Identified Discussion

Gene

A region of DNA that gives rise to an RNA transcript

Pleiotropic Genes

Genes that are involved in more than one function

Allele

a specific DNA sequence of a gene that encodes for a protein or RNA

Homologous Chromosomes

Chromosomes that are the same size, centromere position, and contain the same genes in the same order, though alleles may differ

Locus

The region where a gene is located

Mutation

A change in the sequence of nitrogenous bases in the DNA

Spontaneous Mutation

Caused by replication error exposure to mutagens, not due to external factors/environment

Single Base Mutation

Substitutions, insertions, deletions

Multiple Base Mutation

chromosomal rearrangements and translocations that affect kilobases or megabases of DNA

Background Level Mutation

the rate at which spontaneous mutations accumulate due to unrepaired changes

Point Mutation

A change in a single nucleotide base pair

Transitions Point Mutation

mutations that change a purine to another purine or a pyrimidine to another pyrimidine

Transversion Point Mutation

mutations that change a purine to a pyrimidine or vice versa

Silent Mutation

A mutation that does not change the amino acid sequence (Same Amino Acid)

Missense Mutation

A mutation that results in a different amino acid being incorporated into a protein

Nonsense Mutation

A mutation that creates a premature stop codon in the protein sequence

Neutral Mutation

A mutation that results in a different amino acid, but one that is chemically similar

Frameshift Mutation

A mutation that shifts the reading frame of the genetic code, changing the entire sequence downstream

Dominant Allele

An allele whose phenotype is always expressed, even in heterozygous organisms

Recessive Allele

an allele whose phenotype is only expressed when two identical copies are present

Wildtype

The phenotype generally found in the natural population, not necessarily dominant

Mutant

Any phenotype different from the natural population

Forward Mutation

A mutation that adversely affects the wildtype phenotype

Back Mutation

a mutation that reverts a mutant back to the wildtype phenotype

True Reversion

A mutation changes the mutant DNA sequence back to the exact original wildtype

Second-site reversion

A second mutation in the same gene that compensates for the effect of the first mutation

Suppressor Mutation

A second mutation in a different gene that compensates for the primary mutation

Null Mutation

a mutation that eliminates the function of the entire polypeptide or a critical domain

Hypomorphic Mutation

Some activity of the polypeptide is reduced, or less gene product is made

Hypermorphic Mutation

a mutation that results in an overactive polypeptide, producing too much product

Neomorphic Mutation

New activity is acquired

Antimorphic Mutation

The new function is against the old activity

Haploinsufficiency

1 copy of WT allele is not enough to express the phenotype = LOF phenotype is expressed

Purpose of Complementation Test

To determine if two mutation of a specific phenotype are in the same gene or different genes.

Complements

Progeny looks like the wild type meaning the mutation occurred in two different genes

Fails to complement

Progeny looks mutant meaning the mutations occurred in the same gene.

LOF Mutations

Apomorphic and Hypomorphic Mutations

GOF Mutations

Hypermorphic, Neomorphic, and Antimorphic Mutations