Natural exposure of an organism to certain environmental factors, such as
ultraviolet light and chemical carcinogens
(e.g., aflatoxin B1), also can cause mutations.
What causes both spontaneous and induced mutations?
Spontaneous mutations can occur because of
replication errors
or as a consequence of lesions introduced into DNA during normal cell growth. Induced mutations arise after treatment of the organism with an exogenous mutagen being physical or chemical agent increasing the frequency of mutations.
What is the most common spontaneous mutations?
Two of the most frequent spontaneous lesions result from
depurination and deamination
. Depurination, the more common of the two, consists of the interruption of the glycosidic bond between the base and deoxyribose and the subsequent loss of a guanine or an adenine residue from the DNA (Figure 16-7).
What are some common causes of mutations?
A mutation is a change that occurs in our DNA sequence, either due to mistakes when the DNA is copied or as the result of environmental factors such as
UV light and cigarette smoke
. Mutations can occur during DNA replication if errors are made and not corrected in time.
What is a spontaneous mutation give an example?
Spontaneous mutations in mice may result in
benign phenotypes
, such as variable coat colors, or in disorders that have similarities to diseases in man, for example, the hyperphosphatemia (Hyp) mouse, which is representative of X-linked hyperphosphatemia in man.
What is the difference of spontaneous and induced mutation?
The three sources of spontaneous mutations are the errors in DNA replication, spontaneous lesions like depurination and deamination, and transposable genetic elements. Induced mutations
occur due to the incorporation of base analogs, base mispairing, and base damage produced due to mutagens
.
What do you mean by spontaneous and induced mutation?
Spontaneous mutations can occur because
of replication errors or as a consequence of lesions introduced into DNA during normal cell growth
. Induced mutations arise after treatment of the organism with an exogenous mutagen being physical or chemical agent increasing the frequency of mutations.
What are 3 causes of mutations?
Mutations can result from
DNA copying mistakes made during cell division
, exposure to ionizing radiation, exposure to chemicals called mutagens, or infection by viruses.
What are the 4 types of mutation?
- Germline mutations occur in gametes. Somatic mutations occur in other body cells.
- Chromosomal alterations are mutations that change chromosome structure.
- Point mutations change a single nucleotide.
- Frameshift mutations are additions or deletions of nucleotides that cause a shift in the reading frame.
What causes a spontaneous mutation?
Mutations arise spontaneously at low frequency owing to the
chemical instability of purine and pyrimidine bases
and to errors during DNA replication. Natural exposure of an organism to certain environmental factors, such as ultraviolet light and chemical carcinogens (e.g., aflatoxin B1), also can cause mutations.
Can stress cause genetic mutation?
It has been shown that
certain molecular mechanisms can lead to increased mutation rates
when the organism finds itself in a stressful environment. While this may be a correlated response to other functions, it could also be an adaptive mechanism, raising mutation rates only when it is most advantageous.
What are the causes and effects of mutation?
Mutations can also be
caused by exposure to specific chemicals or radiation
. These agents cause the DNA to break down. This is not necessarily unnatural — even in the most isolated and pristine environments, DNA breaks down. Nevertheless, when the cell repairs the DNA, it might not do a perfect job of the repair.
What occurs in a deletion mutation?
A deletion mutation occurs when
a wrinkle forms on the DNA template strand and subsequently causes a nucleotide to be omitted from the replicated strand
(Figure 3). Figure 3: In a deletion mutation, a wrinkle forms on the DNA template strand, which causes a nucleotide to be omitted from the replicated strand.
What is mean by spontaneous mutation?
A ‘naturally’ occurring mutation in the absence of a mutagen
that would otherwise be a known factor for inducing a particular mutation.
When do random or spontaneous mutations happen?
Current research suggests most spontaneous mutations occur as
errors in the repair process for damaged DNA
. Neither the damage nor the errors in repair have been shown to be random in where they occur, how they occur, or when they occur.
How often do spontaneous mutations occur?
Spontaneous mutations occur at a frequency of
10−5–10−6 per locus per generation
due to misincorporation by DNA (or RNA) polymerases.
