assignment Figure 1 shows a DNA damage that has arisen as a result of ultraviole

Question

assignment

Figure 1 shows a DNA damage that has arisen as a result of ultraviolet light irradiation.

1) What is called the type of DNA damage shown and which bases are included in the damage?
2) Name and describe the two repair processes, each of which can eliminate the type shown
DNA damage in prokaryotic cells. Name the enzymes that are part of the processes and explain
their functions.
It happens rarely that the DNA damage shown is not being repaired. In such case, the DNA polymerase tends to insert a single A to the displayed DNA damage during the replication of the damaged DNA strand. This type of mutation has just happened in a particular protein-coding gene. This gene's mRNA looked before the damage as shown below:
5 '... AUG GCC GAG CCA GUG UUA GGG AGU ... 300 nucleotides ... .CUC UAG ... 3'
The mutation occurs before the 300 unspecified nucleotides. The 300 unspecified nucleotides encode 100 unspecified amino acids. The mRNA is translated into it
indicated reading frame.
3) Write down the sequence of the mRNA generated by transcription of the mutated gene.
What change occurs in the decoding of the mRNA as a result of the mutation and which
Consequence does this have for the polypeptide encoded by the mutated gene? Write down
the amino acid sequence encoded by the normal or the mutated gene (exclude those
unspecified amino acids from the sequence).

Explanation / Answer

1. Pyrimidine dimer. Bases shows are Thymine
2. photoreactivation repair - Energy from visible light is utilized to break the cyclobutane ring structure.
Excision repair, the uvr system excises the dimer, and the gap is filled in by the proof-reading activity of DNAPol I.

Thymidine Dimers are produced when adjacent thymidine residues are covalently linked by exposure to ltraviolet radiation. Covalent linkage may result in the dimer being replicated as a single base, which results in a frameshift mutation.

3. Mutated mRNA seq - AUG GCC GAG CCA GUG UAG GGA GU

The stop codon occurs due to Frame shift mutation.
Consequence does this have for the polypeptide encoded by the mutated gene is Truncated protein or nonfunctional protein.

Normal - Met-Ala-Glu-Pro-Val-Leu-Gly-Ser
Mutated - Met-Ala-Glu-Pro-Val-stop codon

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