Exam 2: Mutations I Flashcards
define a somatic mutation
arise in tissues other than those that produce gametes and impact is restricted to the individual
arise post fertilization an ex is cancer
define a germ-line mutation
arise in tissue that produce gametes and can be passed to offspring
from mom and dad; incorporated in gametes
are mutations always harmful?
no; mutations are building blocks for evolution as mutations can be functionally better than original gene for the environment the organism is in
somatic mutations occur in _ cells and are passed to new cells through _
nonreproductive cells and are passed to new cells through mitosis creating a clone of cells having the mutant gene population of mutant cells
germ-line mutations occur in cells that give rise to _ through _
cells that give rise to gametes, meiosis and sexual reproduction allow germ line-line mutations to be passed to approx half the members of the next generation who will cary the mutation in ALL THEIR CELLS
de novo mutations
an 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 (sperm/egg) of one of the parents or in the fertilized egg itself.
de novo can be either germ line or somatic?
yes
de novo mutations get greater attention when determining pathological causation why?
a de novo mutation happens for the first time in a family (usu during meiosis during replication an aa change happens) neither mom or dad has it so its brand new and gets a marker for being important as it is not inherited
a base substitution alters a _
single codon
insertions and deletions, 2 types
frameshift mutations
in-frame insertions and deletions
an insertion or a deletion alters _
the reading frame and may change many codons
expanding nucleotide repeats
increase in the number of copies of a set of nucleotides
a transition is the substitution of
a purine for a purine or a pyrimidine for a pyrimidine
a transversion is the substitution of
a pyrimidine for a purine or a purine for a pyrimidine
trinucleotide repeat mutations increase
generationally
trinucleotide repeat mutations (expansion) leads to
inactivation of product of a gene ex fragile x and huntington’s disease
trinucleotide repeat mutations (expansion) leads to
increases generationally, results in inactivation of product of a gene ex fragile x (fragile site where repeat is expanded as tendency for mistakes to happen)
neutral mutation
missense mutation that ALTERS THE AA seq but does not change the function of the protein
neutral mutation
missense mutation that ALTERS THE AA seq but does not change the function of the protein
tolerant bc aa seq change may come from the same family of aas and/or stretch of protein is not critical to protein fcn
silent mutation
mutation changes the codon seq but not the aa
new codon encodes the same aa; no change in aa seq
missense mutation
missense mutation is when the change of a single base pair causes the substitution of a different amino acid in the resulting protein. This amino acid substitution may have no effect, or it may render the protein nonfunctional.
new codon encodes a diff aa; there is a change in aa seq
nonsense mutation
mutation that changes a sense codon into a termination codon
new codon is a stop codon thus premature termination of translation; truncation
reverse mutation
mutation that changes the mutant phenotype back into the wild-type
what it important of conserved aa seqs
if an aa seq does not change over time it means that the seq is efficient and needs to be conserved bc it is already optimal
what is expansion
expansion of trinucleotides
if a nucleotide does not change a codon (change in aa), does it have no effect?
not all detrimental mutations are in the coding part of the protein, can be in noncoding. ex is tsar royal family where nucleotide change resulted in loss of splice site; changed aas but not coding part of genome but in splice site. lose exon or gain intron = a lot of aa shuffling
we generally think of mutations affecting the coding seq, but they often impact:
the promoter, 5’ or 3’ noncoding seqs, splice jxns, enhancers
silent or synonymous mutations change the _ but not the _
changes the codon seq but not the aa
redundancy of genetic code
CHARGE syndrome: dna seq analysis of the coding region of the CHD7 gene identified a heterozygous predicted disease-associated nonsense seq variant
is the mutation dominant or recessive?
has to be dominant bc child has one bad and one good copy, but is displaying phenotype so must be dominant
gain of function mutation
produces an entirely new trait of causes it to appear in an inappropriate tissue or at an inappropriate time (ex constitutive activation)
suppressor mutation
genetic change that hides or suppresses the effect of another mutation turned off inappropriately
intragenic suppressor mutation
occurs in same gene as that containing the mutation being suppressed
may alter mutated codon, or re-establish the frame (reverse) if there was a previous frame shift
intergenic suppressor mutation
occurs in gene other than the one bearing the original mutation
intergenic suppressor mutation
occurs in gene other than the one bearing the original mutation
in other genes, perhaps a pathway, and changes the consequences of a mutation in another gene
characteristics of insertion mutation
addition of one or more nucleotides
characteristics of deletion mutation
deletion of one or more nucleotides
characteristics of frameshift mutation
insertion or deletion that alters the reading frame of a gene
characteristics of in-frame deletion or insertion
deletion or insertion of a multiple of 3 nucleotides that does not alter the reading frame
characteristics of expanding nucleotide repeats
increases the number of copies of a set of nucleotides
characteristics of missense mutation
changes a sense codon into a different sense codon, resulting in the incorporation of a different aa in the protein
characteristics of nonsense mutation
changes a sense codon into a nonsense (stop) codon, causing premature termination of translation
characteristics of silent mutation
changes a sense codon into a synonymous codon, leaving the aa seq of the protein unchanged
characteristics of a neutral mutation
changes the aa seq of a protein w/o altering its ability to function
characteristics of loss of function mutation
causes a complete or partial loss of function
characteristics of gain of function mutation
causes the appearance on a new trait or function or cause the appearance of a trait in inappropriate tissue or at an inappropriate time
characteristics of lethal mutation
causes premature death
factors affecting mutation rates (4)
- frequency w/ 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 causes adaptive mutation (2)
- genetic variation critical for evolutionary change that brings about adaptation to new environments
- stressful conditions, where adaptation might be necessary to survive, induce increased mutation in bacteria
mutations that were inherited from a parent describes what time of mutation
germ-line
t/f: mutations provide the raw material for evolution
true
