MCB Mutations

What is a mutation?

an inherited change in genetic information

What is a spontaneous mutation?

occurs in absence of known mutagen; naturally occur in cells

What is an induced mutation?

occurs in presence of known mutagen; chemically induced by mutagens or radiation

What is a somatic mutation?

occurs in nonreproductive cells

What is a germ-line mutation?

occurs in reproductive cells, passed on to all the cells in a person’s progeny

What is a base substitution mutation?

one base pair in duplex DNA replaced with a different base pair

What is a transition mutation?

pyrimidine to pyrimidine, or purine to purine

What is a transversion mutation?

pyrimidine to purine, or purine to pyrimidine

What is an insertion?

one or more extra nucleotides present

What is a deletion?

one or missing nucleotides

What is a synonymous (silent) mutation?

no change in amino acid encoded

What is a missense (nonsynonymous) mutation?

change in amino acid encoded

What is a nonsense mutation?

creates translational termination codon (UAA, UAG, or UGA)

What is a frameshift mutation?

shifts triplet reading of codons out of the correct phase

What can single base changes result in?

protein level changes

What can mutations in protein-coding region change?

an amino acid, truncate the protein, or shift the reading frame

Where are anticodons found?

on tRNAs and are complementary to the codons

What are mutations a source of?

variation in a population and at the heart of evolution

What is anticipation?

the number of repeats tends to correlate with the age of onset and severity of the disease and tends to worsen with subsequent generations

What is strand slippage?

can occur during DNA replication and cause small insertions or deletions

What is fragile-x syndrome?

an excessive number of copies of the CGG repeat

What is a conditional mutation?

expressed only under restrictive conditions (such as high temperature); ex. siamese cats

What is an unconditional mutation?

expressed under permissive conditions as well as restrictive conditions

What is a loss-of-function mutation?

eliminates normal function

What is a gain-of-function mutation?

expressed at incorrect time or in inappropriate cell types

DNA is considered:

accurate; less than 1 error in a billion nucloetides

What is deamination?

a spontaneous chemical change; removing an amino group from a molecule

What produces insertions and deletions?

unequal crossing over in meiosis I

What are mutagens?

chemicals that can cause mutations in DNA; induced mutations

What are base analogs?

chemicals with structures similar to that of nucleotides

What occurs if base analogs are present?

DNA polymerase cannot distinguish them and will incorporate in DNA

What is excision repair?

excise stretch of DNA containing dimer (pairs) on the same strand of DNA and correct “mistake” using a template

What is a mismatch repair?

repair secondary structure of helix containing incorrect pairs

What is forward genetics?

phenotype —> mutation

What is reverse genetics?

mutation —> phenotype

What is a neutral mutation?

changes the amino acid sequence of a protein without altering its ability to function

What is a nucleotide excision repair?

replacement of up to 30 nucleotides, correct several types of DNA damage

What is a base excision repair?

replacement of one to five continuous DNA nucleotides, which corrects oxidative damage

What is a splice site mutation?

causes an exon to be skipped

What is a tandem duplication?

consists of two copies of a gene located next to each other on a chromosome

What is a copy number variant?

DNA sequences that vary in number

What can a mutation to a synonymous codon affect?

mRNA splicing and stability

What are pseudogenes?

can lead to mispairing in meiosis, can ultimately lead to deletions

What are transposons?

can jump into genes, disabling them