Genetics Mutation Flashcards
[…] are random and rarely occur. Genotypic mutation rate is the number of mutations that happen per replicated […]. Mutations at the DNA level are low and similar in different […]; about 10^-9 per replicated base pair
Gene mutations; base pair; organisms
Genes with elevated mutation rates are called […]. One reason for mutation hotspots is large […] size. For example, the […] gene associated with Duchenne muscular dystrophy and the […] gene associated with neurofibromatosis are large genes each with a mutation rate of about 10 ^ -4.
mutation hotspots; gene; DYS; NF1
Mutations that occur in […] cells, giving rise to sperm and egg, are called germ-line mutations. Germ-line mutations can be passed from one […] to the next. Cells not in the germ line are […] cells; thus mutations in such cells are called somatic mutations. Somatic cells divide by […] and only direct descendants of the original mutated cell will carry the mutation
germ-line; generation; somatic; mitosis
Most commonly, gene mutations substitute, add, or delete one or more […]. Localized mutations, or […] mutations, occur at a specific, identifiable position in a gene or a specific location anywhere else in the genome. Such mutations have varied […] depending on the type of sequence change and the location of the affected part of the gene
DNA base pairs; point; consequences
Base-pair substitution mutations: the replacement of one […] by another. 2 types: […] mutations: one purine replaces another, or one pyrimidine replaces another . […] mutations: a pyrimidine is replaced by a purine or vice versa
nucleotide base pair; Transition; Transversion
[…] mutation: a base-pair change that does not alter the resulting amino acid due to the redundancy of the genetic code (AKA Silent mutation). […] mutation: a base-pair change that results in an amino acid change in the protein. […] mutation: a base-pair change that creates a stop codon in place of a codon specifying an amino acid
Synonymous; Missense; Nonsense
Insertion or deletion of one or more base pairs leads to addition or deletion of […], which may alter the reading frame of the message. These are called […] mutations. The […] amino acid sequence is produced starting at the point of mutation; premature stop codons may also be produced
m R N A nucleotides; frameshift; wrong
Some point mutations […] the amount (but not the amino acid sequence) of protein product produced by a gene. These […] mutations affect regions such as promoters, introns, and the regions coding for 5’-UTR and 3’-UTR segments. Three types of regulatory mutations are recognized: […], […], […].
alter; regulatory; Promoter; Splicing;
Polyadenylation
Mutations that alter consensus sequence nucleotides of promoters are called […] mutations. These interfere with […] transcription initiation. Some promoter mutations cause mild to moderate reductions in transcription levels, whereas others may […] transcription
promoter; efficient; abolish
Efficient splicing of introns from m R N A requires […] at either end of the intron.
Mutations that alter these nucleotides are called […]. These can result in splicing errors and the production of mutant proteins due to the […] of intron sequences in the m R N A
specific sequences; splicing mutations; retention
Some base-pair substitution mutations produce new splice sites that replace or compete with authentic splice sites during […]. These are called […] splice sites. A base-pair substitution changing […] at position 110 of human β-globin intron 1 creates an A G cryptic splice site
This leaves […] additional nucleotides in the mature mRNA
mRNA processing; cryptic; G to A
Mutation of the […] signal sequence at the 3’ end of eukaryotic mRNA can block the proper 3’ processing of mRNA. This occurs in a […] mutant form of the human α-globin gene, leading to severe reduction in functional α-globin protein produced
polyadenylation; rare
[…] mutation: converts a wild-type allele to a mutant allele. […] mutation or [..]: converts mutant alleles to wild-type or near wild-type allele. […] reversion: wild-type DNA sequence is restored by a second mutation within the same codon
Forward; Reverse; reversion; True
[….] reversion: occurs through second mutation elsewhere in the same gene
[…] reversion: occurs by mutation in a different gene that compensates for the original mutation, restoring the organism to wild-type. Second-site reversions are also known as […] mutations because the second mutation “suppresses” the mutant phenotype caused by the first mutation
Intragenic; Second-site; suppressor
[…] mutations arise in cells without exposure to agents capable of inducing mutation. These arise primarily through errors in […] or spontaneous changes in the chemical structure of a nucleotide base.
Spontaneous; DNA replication
D N A replication has very high fidelity due to the accuracy of [….], the “proofreading” ability of D N A polymerases, and the efficiency of mismatch repair. […] due to replication errors occur at a rate of about 1 x10^-9 in wild-type E. coli and about the same in eukaryotes.
DNA polymerases; Mismatches
Alterations in number of D N A repeats occur via […]. The D N A polymerase of the replisome temporarily dissociates from the template and a portion of the newly replicated D N A forms a temporary […]. Resumption of replication leads to […] of some of the repeats and an overall increase in the number of repeats on the daughter strand
strand slippage; hairpin; re-replication
[….] repeat expansion disorders involve strand slippage mutations that cause some hereditary diseases in humans and other organisms. […] alleles of the genes in question normally have a variable number of DNA trinucleotide repeats. Increases in the number of repeats beyond a certain threshold cause the […].
Trinucleotide; Wild-type; disorders
[….] base pairing, similar to third-base wobble, sometimes occurs during D N A replication and is called non–Watson-and-Crick base pairing. These include G with T pairing or C with A pairing; this type of […] is identified as incorporated error. Without repair, replication of the incorporated error converts it into a mutation in an event called […].
Non-complementary; mispairing; replicated error
Depurination; apurinic site; DNA polymerase
Deamination; oxygen; mismatch
When […] cytosine is deaminated, a thymine base is produced, which is now base-paired with guanine. The mismatch repair system can restore the […] G-C pair. If repair does not occur, the G-T pair remains and replication will produce two […], one with the mutant A-T pair and one with the wild-type G-C pair
methylated; wild-type; sister chromatids,
Agents that cause DNA damage leading to mutations are called […]. […] mutations are produced by mutagens in an experimental setting to study types of damage caused, the mutation process itself, or repair responses to damage
Mutagens interact with […] in specific ways to cause particular types of sequence changes
mutagens; Induced; DNA
Chemical mutagens can be classified by their modes of action on D N A as follows: […] base analogs; […] agents; [….] agents; [….] agents; […] agents; […] agents
Nucleotide; Deaminating; Alkylating; Oxidizing; Hydoxylating; Intercalating
A nucleotide base analog is a […] with a structure similar to a D N A nucleotide base. These can pair with normal nucleotides—D N A polymerases cannot […] the analogs from normal nucleotides
For example, 5-bromodeoxyuridine acts as an analog of […].
chemical compound; distinguish; thymine
A deaminating agent […] amino groups from nucleotide bases. Deamination of adenine by nitrous acid produces […], which can mispair and lead to A-T to G-C base-pair substitutions
removes; hypoxanthine
[….] agents added bulky side groups such as methyl (CH3) and ethyl (CH3-CH2) groups to bases. Ethyl methanesulfonate (E M S) is a [….] alkylating agent. Addition of bulky side groups interferes with D N A base pairing by […] the D N A double helix
EMS induces […] mutations through its action on guanine.
Alkylating; powerful; distorting; transition
Hydroxylating agents add […] to a recipient compound. Hydroxylamine adds a hydroxyl group to […], creating hydroxylaminocytosine. This can mispair with adenine, creating a C-G to T-A […].
hydroxyl groups; cytosine; transition mutation
Some molecules are able to fit between […]. These D N A intercalating agents distort the […]. The distortion may result in […] due to added or lost nucleotides
DNA base pairs; DNA duplex; frameshift mutations
[…] are aberrant structures with additional bonds involving nucleotides; caused by UV irradiation. One common photoproduct is a […], formed by covalent bonds between the 5 and 6 carbons of adjacent thymines. A second is called a 6-4 photoproduct, formed by a […] between the 6 carbon on one thymine and the 4 carbon on the other
Photoproducts; thymine dimer; covalent bond
DNA repair systems of most organisms can identify and correct most […]. Those that are not repaired cause disruption of […]. Such disruptions leads to mutations; these are the primary cause of the strong association between excessive […] and skin cancer
pyrimidine dimers; replication; UV exposure
The […] test mimics what happens when animals are exposed to compounds, and determines if the compound or any of its breakdown products is mutagenic. […] are exposed to experimental compounds in the presence of mammalian liver enzymes. In animals, […] chemicals are transported to the liver, where they are broken down by enzymes.
Ames; Bacteria; ingested
Most commonly, […] of Salmonella typhimurium are used. They carry various types of mutations (frameshift or base substitution) interfering with their ability to synthesize […]. The bacteria are exposed to the chemical to be tested, plus an extract of […], and plated on medium lacking histidine
strains; histidine; purified liver enzymes
The number of […]. mutations from his− to his+ are assayed. The suggestion that a compound is mutagenic is shown by a significant increase in the […] in treated strains relative to controls. This includes strains with one type of mutation (base substitution) compared to those with another (frameshift), and […].
reversion; reversion rate; untreated strains
