Mutation, variants and Polymorphism Flashcards
Where do these alleles come from?
Mutation
What is mutation?
causes either a partial or complete loss of function, but sometimes results in a gain of function,including new functions
Something undersirable or broken and when a variation in DNA sequence originated recently, and is rare in a population
mutation
If a mutation changes the phenotype of an individual, the individual is said to be
Mutant
variants of DNA sequences (and other phenotypes) that co-exist in a population at relatively high frequencies (>1%).
Polymorphism
a difference in DNA sequence that explains whether a person has red hair rather than brown or black hair is an example of
Polymorphism
types of mutation
- Deletion
- substitution
- insertion
Mutations may either occur ____, or may be induced by exposure to _______.
Spontaneously, mutagens
arise from many sources including natural errors in DNA replication, usually associated with base mispairing, or else insertion deletion especially within repetitive sequences.
Spontaneous mutations
Result from mispairing, DNA damage, or sequence interruptions caused by chemical, biological, or physical mutagens.
Induced mutations
By randomly ________, then screening for a ________, it is possible to identify genes associated with specific biological pathways.
inducing mutations, specific phenotype
____________ are dynamic, abundant components of eukaryotic genomes and important forces in evolution.
Transposable elements
limited by silent mutations, redundancy, and embyronic lethality.
The efficiency of mutant screening
Mutation of different genes can produce a similar ________.
phenotype
Complementation testing determines whether two mutants are the result of mutation of the same gene (__________), or if each mutant is caused by mutation of a different gene (_______).
(allelic mutations), (non-allelic mutations).
This ______ causes one or more bases on either strand to be temporarily displaced in a ____ that is not paired with the opposite strand. If this ____ forms on the _________, the bases in the loop may not be ________, and a _______ will be introduced in the growing daughter strand. Conversely, if a region of the daughter strand that has just been ________ becomes displaced in a ______, this region may be ______ again, leading to an ________ of additional sequence in the daughter strand, as compared to the template strand.
strand-slippage, loop, loop, template strand, loop, replicated, deletion, replicated, loop, replicated, insertion
Mispairing of bases (e.g. G with T) can occur due to
- tautomerism
- alkylating agents
- or other effects.
occur occasionally during replication, especially in regions with short, repeated sequences. This can lead to either deletion (left) or insertion (right) of sequences compared to the products of normal replication (center), depending on whether the template strand or daughter strand “loops-out” during replication.
Strand-slippage
Thus regions with ____ are tend to be highly polymorphic, and are thereforecparticularly useful in genetics. They are called
short-sequence repeats
(SSRs), microsatellites
may disrupt the coding or regulatory sequence of a gene, including the fusion of part of one gene with another.
insertion
insertions can occur spontaneously, or they may also be intentionally stimulated in the laboratory as a method of mutagenesis called
transposon-tagging
an insertional element modified from a bacterial pathogen, is used as a mutagen in some plant species.
T-DNA
Transposable elements (TEs) are also known as
mobile genetic elements, or more informally as jumping genes.
They are present throughout the chromosomes of almost all organisms. These DNA sequences have a unique ability to be cut or copied from their original location and inserted into new locations in the genome.
Transposable elements
