Base analogs are molecules that can substitute for normal bases in DNA and RNA. They have a similar structure to adenine, guanine, cytosine, or thymine but can pair with multiple natural bases. This affects DNA replication and transcription, leading to mutations. Option C, 5-bromouracil, is identified as a base analog that is used to treat cancer because it substitutes for thymine and pairs with both adenine and guanine during DNA replication, causing mutations.

1. BASE
ANALOGS
BIBHU PRASAD
RATH
LECT. IN BOTANY

2. Which one of the following is a base
analogue [BHU 1984]
• A) Nitrous acid
• B) Colchicine
• C) 5 - bromouracil
• D) Caffeine acycloguanosine

3. • Base analogues are molecules that can
substitute for normal bases in nucleic acids.
• Base analogs are molecules which have a very
similar structure to one of the four
nitrogenous bases which are used in DNA
(adenine, guanine, cytosine or thymine).
5-bromouracil

4. • Usually, substitution of a base analogue will
result in altered base pairings and structural
changes that affect DNA replication and
transcription of genes.
• 5-bromouracil, 2-aminopurine, 6-
mercaptopurine, and acycloguanosine
2-aminopurine

5. • Since 5-bromouracil can pair with either
adenine or guanine, it also affects base
pairing during DNA replication, which leads
to mutations.
• An analogue of adenine, 2-aminopurine, also
causes mutations in a similar way since it can
pair with either T or C.
6- mercaptopurine

6. • Neoplasm, a new and abnormal
growth of tissue in a part of the
body, especially as a
characteristic of cancer.
• 5-Bromouracil is used to treat
neoplasms.
Image courtesy:
https://en.wikipedia.org/wiki/Neoplasm