MG Ch. 15 Flashcards
(T/F)Tautomers of nucleotide bases are isomers that differ from each other in the location of one hydrogen atom in the molecule.
True. Tautomeric shift differ by 1 proton
Which nucleotide will base‑pair with the enol form of 5‑bromouracil?
Guanine.
5-bromo replaces Adinine with Thiamine, after 1 replication cycle it binds to guanine
The outcome of a tautomeric shift is?
change the bonding structure of the molecule, making non-complementary base-pairing possible.
(T - G or C - A paring)
Which of the following events could result in a frameshift mutation? Tautomeric shift Base deletion Point mutation Incorporation of base analogs
Base deletion
A base deletion would shorten the DNA sequence and change the reading frame of the mRNA.
Generally speaking, which of the following mutations would most severely affect the protein coded for by a gene?
a frameshift deletion at the beginning of the gene
A frameshift mutation at the beginning of a gene would affect every codon after the point where the mutation occurred. During protein synthesis, incorrect amino acids would be inserted from the point where the frameshift mutation occurred on; the resulting protein would most probably be nonfunctional. For this reason, a frameshift mutation at the beginning of a gene is generally the most severe type of mutation
5’ - C A A - 3’
3’ - G T T - 5’
Suppose that a transient tautomeric shift occurred in the guanine base to produce a rare tautomer in the partial DNA sequence just prior to a round of DNA replication.
Which base would be added opposite this rare tautomer during DNA replication?
Thiamine
What is tautomeric shift?
Tautomeric shift is an intramolecular proton shift that changes the bonding structure of the molecule
Why are X rays more potent mutagens than UV radiation?
X rays are of higher energy and shorter wavelength than UV light. They have greater penetrating ability and can create more disruption of DNA.
What is a spontaneous mutation?
Mutations that occur as a result of natural biological and/or chemical processes are considered spontaneous.
Which repair mechanism is most likely affected if the enzyme DNA glycosylase is not functioning properly?
base excision repair
Adenine methylase is an enzyme used during mismatch repair (MMR). It helps determine which strand needs to be repaired by discriminating between the template and new DNA strand. If this enzyme is mutated, how would MMR be affected?
MMR would be hindered because both strands would be unmethylated and both would appear as new DNA strands and it would not be able to determine which strand has the error.
What is the difference between a transition and a transversion mutation?
Transition - pyrimidine replaces another pyrimidine
Transversion - Pyrimidine replace a purine
One might suggest that transposons are more likely to insert in noncoding regions of the genome because they are _____ in those regions
more stable
It is possible that transposons insert ____ and that selection eliminates those that have interrupted ___ regions of the genome.
such regions are _____ to influence the phenotype.
randomly
coding
more likely
