Answer to Question #165679 in Genetics for Virat

Question

3) Chemical elements of tobacco smoke can change the nucleotide sequence in a DNA molecule by

replacing adenine with thymine or guanine with cytosine. Which kind of mutation is this one? Draw and

explain the mechanisms and consequences of such a change.

Answer 1

Chemicals in tobacco cause a type of point mutation known as transition mutation. Transition mutation causes the replacement of one purine (Adenine, Guanine) base with a pyrimidine (Cytosine, Thymine) base or otherwise the replacement of one pyrimidine base with a purine base. Transversion mutations are caused by either ionizing radiations or by alkylating agents. Spontaneous germline transversion is one of the well-demonstrated mechanisms by which transversion mutations occur, it is a function of 8-oxodG (8-oxo-2' -deoxyguanosine) , an oxidized derivative of deoxyguanosine, a product of DNA oxidization. During replication, the oxidized base 8-oxoguanine causes spontaneous and heritable transversion mutations of Guanine to Thymine bases. The common consequences of this type of mutation are a possibility of; change in the protein sequence or commonly silent mutations, changes in amino acid sequence or missense mutations or create a stop codon.