Lecture 19 Flashcards
What is a somatic mutation?
Arise in tissues other than those that produce gametes; impact is restricted to the individual
What is a germ-line mutation?
Arise in tissues that produce gametes; can be passed to offspring
What is a de novo mutation?
Alteration in a gene that is present for the first time in one family member as a result of a mutation in a germ cell of one of the parents or in the fertilized egg itself; can be either somatic or germ-line
What is a missense mutation?
Base substitution that results in a different AA
What is a nonsense mutation?
Mutation that changes a sense codon into a termination codon
What is a loss of function mutation?
Causes the complete or partial absence of a normal protein function; usually recessive
What is a neutral mutation?
Missense mutation that alters the AA sequence but does not change the function of the protein
What is a silent mutation?
Mutation that changes the codon sequence but not the AA
What are suppressor mutations? What are the categories?
Suppressor Mutation: genetic change that hides or suppresses the effect of another mutation
Intragenic: occurs in same gene as that containing the mutation being suppressed
Intergenic: occurs in gene other than the one bearing the original mutation
Explain InDels
Result when unequal crossing over produces one chromosome that has an insertion and one chromosome that has a deletion; these are small insertions/deletions
What is the significance of base analogs?
These chemicals have structures that are similar to normal bases that can act as a normal base, but may mispair with other bases in the sequence; for example, 5-bromouracil, an analog of thymine, usually pairs with A but may mispair with G while 2-aminopurine normally pairs with thymine but may mispair with a C; this can lead to replication errors
What are expanding nucleotide repeats?
Increase in the number of copies of a set of nucleotides
What is a forward mutation?
Mutation that alters the wild-type phenotype
What is a reverse mutation?
Mutation that changes the mutant phenotype back into the wild-type
What is a gain of function mutation?
Produces an entirely new trait or causes it to appear in an inappropriate tissue or at an inappropriate time
What is an insertion and what is a deletion mutation?
Insertion: addition of one or more nucleotides
Deletion: deletion of one or more nucleotides
What is a frameshift mutation?
Insertion or deletion that alters the reading frame of a gene
What is an inframe deletion or insertion mutation?
Deletion or insertion of a multiple of three nucleotides that does not alter the reading frame
What is a lethall mutation?
Causes premature death
What are some factors that affect mutation rates?
- Frequency with which a change takes place in DNA
- Probability that when a change takes place, that change will be repaired
- Environmental factors can increase mutation rates
- Genetics background influences mutation rate
What is the mutation that causes fragile-x syndrome?
Trinucleotide repeat mutation; fragile x is associated with a characteristic constriction on the long arm of the chromosome; fragile-x is the most common known genetic cause for mental impairment in boys
