Lecture 14 Mutations and Repair Ch. 18 Flashcards
What are the two major categories of mutations?
Somatic and Germ-line
Somatic mutations arise where?
In tissues other than those that produce gametes
What mutations are restricted to the individual?
Somatic mutations
Germ-line mutations arise where?
In tissues that produce gametes
What mutations can be passed to offspring?
Germ-line mutations
What are transition mutations?
Base substitutions: Purine replaced by purine; pyrimidine replaced by pyrimidine
What are transversion mutations?
Base substitutions: Purine replaced by pyrimidine or vice versa
What are the types of frameshift mutations?
Insertions, and deletions
Describe forward mutations
Mutation that alters the wild-type phenotype
Describe reverse mutation
Mutation that changes the mutant phenotype back into the wild-type
Describe missense mutations
Base substitution that changes the sequence and the meaning of a mRNA codon, resulting in a different amino acid being inserted into a protein
Describe nonsense mutation
Mutation that changes a sense codon into a termination codon
Describe silent mutation
Mutation that changes the sequence of an mRNA codon, but not the meaning
Describe neutral mutation
Missense mutation that alters the amino acid sequence but does not change the function of the protein
What does loss of function mutation cause?
The complete or partial absence of a normal protein function - usually recessive
What does gain of function mutation produce?
An entirely new trait or causes it to appear in an inappropriate tissue or at an inappropriate time
We generally think of mutations affecting the coding sequence, but they often impact what?
The promotor, 5’ or 3’ noncoding sequences, splice junctions, enhancers
Describe suppressor mutation
Genetic change that hides or suppresses the effect of another mutation
Two types:
Intragenic and intergenic
Describe intragenic
Suppressor mutation that occurs in same gene as that containing the mutation being suppressed. Results of the second mutation restores a wild-type phenotype.
Second mutation at a different site in the SAME gene.
Describe intergenic
Suppressor mutation that occurs in gene other than the one bearing the original mutation
DNA pairing is not always perfect, when mispairing due to altered protonation happens what results?
An altered nucleotide that does not get corrected in the next round of replication
Which type of base substitution is usually more common?
Transition mutations
Although transversions would seem to be statistically favored because there are eight possible transversions and only four possible transitions, about twice as many transition mutations are actually observed in the human genome
Briefly describe expanding nucleotide repeats
Expanding nucleotide repeats occur when DNA insertion mutations result in an increase in the number of copies of nucleotide repeat sequence. May account for the penomenon of anticipation.
How can expanding nucleotide repeats occur?
Such an increase in the number of copies of a nucleotide sequence may occur by errors in replication or unequal recombination.