Identifying Genes Discussion

what is a gene?

region of DNA that gives rise to a RNA transcript

what is a pleiotropic gene?

genes that are involved in more than one function

what is an allele?

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

what is the central dogma?

DNA > RNA > polypeptide/protein

what does reverse transcriptase do?

RNA > DNA

what are homologous chromosomes?

chromosomes with the same size, centromere position, and genes located in the same order

what is a locus?

region where a gene is located on a chromosome

what bases are purines?

adenine and guanine

what bases are pyrimidines?

thymines, cytosines, uracil (for RNA)

what is a mutation?

change in the sequence of nitrogenous bases in DNA

what is a spontaneous mutation?

mutation caused by replication error or exposure to mutagens

what is a background level mutation?

rate at which spontaneous mutations accumulate due to unrepaired changes

what is a single base mutation?

substitution (base is swapped out with another), insertion (base pair(s) is added), and deletions (base pair(s) is removed)

what are multiple base mutations?

chromosomal rearrangements or translocations

what happens when a cytosine is deaminated?

transforms into uracil

what happens when a 5-methylcytosine is deaminated?

transforms into thymine

what is a transition point mutation?

purine to purine or pyrimidine to pyrimidine

what is a transversion point mutation?

purine to pyrimidine or vice versa - rarer

what is a silent point mutation?

results in same AA

what is a missense point mutation?

results in one AA being changed

what is a nonsense point mutation?

results in a premature stop codon

what is a neutral point mutation?

results in different AA but the alternate AA is chemically similar - leads to no significant idfferene in protein function

what is a frameshift mutation?

adds or removes base pair(s) - changes entire sequence downstream if not in multiples of 3

what is a dominant allele?

phenotype always expressed

what is a recessive allele?

phenotype only expressed when two identical copies are present

what is a wildtype allele?

phenotype found in natural population

what is a forward mutation?

mutation that negatively impacts wildtype alleles - one polypeptide mutates and interaction is blocked

what is a back mutation?

a mutation that reverts a mutant allele back into a wildtype allele

what is a true reversion?

mutation that changes mutant DNA sequence into exact original wildtype

what is a second-site reversion?

second mutation in the SAME gene that compensates for first mutations effects

what is a suppressor mutation?

second mutation in a DIFFERENT gene that compensates for the first mutation

what is a null (amorphic) LOF mutation?

function is elimiinated from entire polypeptide/critical domain of polypeptide

what is a hypomorphic LOF mutation?

activity of polypeptide is reduced or less gene product is made

what is a hypermorphic GOF mutation?

too much product is produced or funtional domain of polypeptide works more efficiently

what is a neomorphic GOF mutation?

altered gene product gains a completely new function or is expressed in a new tissue or at a new time during development

what is an antimorphic GOF mutation?

altered gene product not only gains a new function but also antagonizes or disrupts the normal function of the wild-type allele - forms a nonfunctional complex

are GOF alleles dominant or recessive?

dominant

are LOF alleles dominant or recessive?

USUALLY recessive, unless haploinsufficiency occurs

what is haploinsufficiency?

one copy of the wild-type allele isn’t enough to produce a phenotype - the LOF phenotype will be expressed

what does the result “complement” mean on a complementation test?

result is fixed, and progeny presents wildtype - due to mutations occuring on different genes

what does the result “failed to complement” mean on a complementation test?

result failed to fix, and progeny looks mutant - due to mutations occuring in the same gene