Lecture #11 Flashcards
How can mutations arise?
spontaneously, as a result of DNA synthesis
What happens when the wrong base pairs are paired by stay due to wobble?
a transition mutation occurs at the next round of DNA replication
What does depurination lead to?
base substitution
What is deamination?
loss of an amino group which changes the type of base pair
What are somatic mutations?
mutations that affect the individual but will not be passed on
What are germ-line mutations?
mutations that will be passed on
What does strand slippage lead to?
Insertions or deletions
What happens if chromosomes misalign during crossing over?
unequal crossing over produces insertions or deletions
What are the two groups of chemical mutagens?
mutagenic only to replicating DNA or mutagenic to both replicating and non-replicating DNA
What are base analogues?
Compounds that mimic nucleotide base pairs
How do base analogues affect DNA?
base analogues can become incorporated into DNA which leads to mispairing and transition mutations
What do oxidative radicals do to DNA?
Damage DNA by chemical changes to nucleotides
What effects do X-rays have on DNA?
can induce chromosome breaks, fusions and translocation
How does UV light effect DNA?
Absorption of UV energy by pyrimidines leads to their dimerization, which leads to distortion of the DNA strand
What effects do acridines have on DNA?
Acridines intercalate between adjacent base pairs and distort the double helix
What are transposable elements?
a transposable elements insert themselves into the DNA and interrupt coding sequences
How is sickle cell anemia caused?
a single base pair change in the beta globin gene
What do mutations that affect non-coding regions do?
Interfere with promotor function to prevent or reduce transcription, or prevent or reduce translation
What is myotonic dystrophy type 1?
CTG expansion in the untranslated region (UTR) of an mRNA transcribed from chromosome 19 encoding an enzyme (kinase)
What is myotonic dystrophy type 2?
CTG expansion in an intron of a gene on chromosome 3encoding a zinc finger transcription factor
What makes an allele dominant or recessive?
Dominant mutation, loss of function mutation, dominant negative mutation, or gain of function mutation
What is a null allele?
A complete loss of function in the recessive allele
What is a hypomorphic allele?
a partial loss of function in the recessive allele
What is a dominant mutation in an allele?
involve a loss OR gain of gene function
What is a loss of function mutation in an allele?
for the genes in which one copy is not enough
What is a dominant negative mutation?
a loss of function mutation that interferes with the normal function of the wild type allele
What is a gain of function mutation?
enhances the normal function of the gene or causes the expression of the gene in the novel cell type
What is the antennapedia mutation in drosophila?
A dominant gain of function mutation in a regulatory region of the Antp gene
What is a missense mutation?
a point mutation in which a single nucleotide change results in a codon that codes for a different amino acid
What is a nonsense mutation?
a point mutation in which a single nucleotide change results in a premature stop codon
What is a frameshift mutations?
When a nucleotide insertion or deletion changes the reading frame of the DNA sequence
What is an expanding mutation?
A duplication mutation that repeats every generation (ex: gen 1 would have 1 duplication, gen 2 would then have 2 and so on)
