Which agent/molecule could cause following changes on DNA? Select from: X-ray, D
ID: 193096 • Letter: W
Question
Which agent/molecule could cause following changes on DNA? Select from: X-ray, DNA polymerase, UV, Alkylating agent, Proflavin, Ac transposon, Ampicilin.
(1) Double-stranded break
(2) Transitional change
(3) Thymine dimer
(4) 8 basepair duplication
(5) Small insertion or deletions
(6) Expansion or contraction of trinucleotide repeats
Synonymous mutation (select as many that apply)
a) Does not cause changes in amino acid.
b) Does not cause any adverse effect to the organism.
c) Is the same as silent mutation.
d) Is the same as neutral mutation.
Explanation / Answer
1.
When the cells are exposed to the ionizing radiation, the direct or indirect action may occur. Direct action takes place when X-rays or beta/alpha particles produces ions that can physically break one or both the strands of the DNA. Therefore, X-ray can cause double-stranded breaks.
2.
Alkylating agents transfer the ethyl or methyl groups to the phosphate group present in the backbone or to the bases. Due to this, it alters the base pairs with the incorrect complement. Therefore, it disrupts the base pairing and may lead to transitional change. Therefore, alkylating agents can cause transitional change.
3.
The UV light leads to the formation of thymine base pairs next to one another in the genetic sequences and bond together into the pyrimidine dimers. This leads to the formation of thymine dimers and adds thymine next to each other. Therefore, UV can cause thymine dimers.
4.
A transposable element refers to the DNA sequence, which alters its location inside the genome. It often leads to the duplication of the gene. The size of the transposable element is 11-bp inverted repeats. Therefore, transposons can cause 8 base-pair duplications.
5.
In an experiment, it was observed that the proflavine-induced mutations lead to the insertion or deletion of a single base pair in the DNA sequence. Therefore, proflavine can cause small insertions or deletions.
6.
Replication slippage is a type of mutation, which leads to the trinucleotide or dinucleotide expansion or contraction at the time of DNA replication. DNA polymerase is the prime enzyme that is responsible for the occurrence of this mutation. Therefore, DNA polymerase can cause expansion or contraction of the trinucleotide.
A synonymous mutation refers to the change in the sequence of the DNA, which codes for an amino acid in the sequence of the protein. However, it does not change the encoded amino acid and hence option (a.) is correct.
It is often considered to be the silent mutations. This can affect the translation, transcription, splicing, and transportation of the mRNA. These mutations do not cause any adverse effects on the organism. It changes the amino acid. Hence, (b.) and (c.) is correct.
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