Fgf

Conclusion: Incorporation of bromouracil followed by mispairing leads to a TA-*■ CG transition mutation.

^ If 5-bromouracil pairs with adenine, no replication error occurs.

4 17.19 5-Bromouracil can lead to a replicated error.

17.20 Chemicals may alter DNA bases, (a) The alkylating agent ethylmethanesulfonate (EMS) adds an ethyl group to guanine, producing 6-ethylguanine, which pairs with thymine, producing a C-G : T-A transition mutation. (b) Nitrous acid deaminates cytosine to produce uracil, which pairs with adenine, producing a C-G : T-A transition mutation. (c) Hydroxylamine converts cytosine into hydroxylaminocytosine, which frequently pairs with adenine, leading to a C-G : T-A transition mutation.

f

Original base

Mutagen

Modified base

Pairing partner

Type of mutation

(a)

0 0

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