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Question
Errors during DNA replication, repair or recombination can lead to base-pair substitution. Such changes are
Errors during DNA replication, repair or recombination can lead to base-pair substitution. Such changes are
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The correct option is D Spontaneous mutations
Spontaneous mutation: A 'naturally' occurring mutation in the absence of a mutagen that would otherwise be a known factor for inducing a particular mutation. Spontaneous mutations on the molecular level can be caused by:1. Tautomerism - A base is changed by the repositioning of a hydrogen atom, altering the hydrogen bonding pattern of that base, resulting in incorrect base pairing during replication.
2. Depurination - Loss of a purine base (A or G) to form an apurinic site (AP site).
3. Deamination - Hydrolysis changes a normal base to an atypical base containing a keto group in place of the original amine group. Examples include C U and A HX (hypoxanthine), which can be corrected by DNA repair mechanisms; and 5MeC (5-methylcytosine) T, which is less likely to be detected as a mutation because thymine is a normal DNA base.
4. Slipped strand mispairing - Denaturation of the new strand from the template during replication, followed by renaturation in a different spot ("slipping"). This can lead to insertions or deletions.
Spontaneous mutation: A 'naturally' occurring mutation in the absence of a mutagen that would otherwise be a known factor for inducing a particular mutation. Spontaneous mutations on the molecular level can be caused by:
1. Tautomerism - A base is changed by the repositioning of a hydrogen atom, altering the hydrogen bonding pattern of that base, resulting in incorrect base pairing during replication.
2. Depurination - Loss of a purine base (A or G) to form an apurinic site (AP site).
3. Deamination - Hydrolysis changes a normal base to an atypical base containing a keto group in place of the original amine group. Examples include C U and A HX (hypoxanthine), which can be corrected by DNA repair mechanisms; and 5MeC (5-methylcytosine) T, which is less likely to be detected as a mutation because thymine is a normal DNA base.
4. Slipped strand mispairing - Denaturation of the new strand from the template during replication, followed by renaturation in a different spot ("slipping"). This can lead to insertions or deletions.
2. Depurination - Loss of a purine base (A or G) to form an apurinic site (AP site).
3. Deamination - Hydrolysis changes a normal base to an atypical base containing a keto group in place of the original amine group. Examples include C U and A HX (hypoxanthine), which can be corrected by DNA repair mechanisms; and 5MeC (5-methylcytosine) T, which is less likely to be detected as a mutation because thymine is a normal DNA base.
4. Slipped strand mispairing - Denaturation of the new strand from the template during replication, followed by renaturation in a different spot ("slipping"). This can lead to insertions or deletions.
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