Question 1

Q: What is the primary molecular mechanism by which UV light induces carcinogenesis?

Thymine dimers. ***Thymine dimers*** - UV radiation, particularly **UVB**, causes structural damage to **DNA** by inducing the formation of **pyrimidine dimers** (specifically cyclobutane pyrimidine dimers involving thymine residues) between adjacent bases. - If these lesions are not effectively repaired by the **nucleotide excision repair (NER)** pathway, they lead to **mutations** (commonly C to T transitions) in critical genes like **TP53** during DNA replication, driving carcinogenesis. *Inhibition of TP53* - While UV damage often leads to mutations in the **TP53 gene**, this is a downstream consequence of DNA damage, not the primary molecular mechanism of UV-induced injury itself. - **TP53** is typically inactivated via **mutations** caused by failed repair of DNA photoproducts, rather than direct inhibition of the protein by UV light. *Activation of NF-kappa beta signaling pathway* - The **NF-kappaB pathway** is primarily involved in **inflammatory and immune responses** rather than being the direct mechanism of DNA damage-induced carcinogenesis. - While UV exposure does activate inflammatory pathways, this is a secondary response to tissue stress and not the foundational cause of **mutagenesis** and cancer initiation. *Upregulation of cyclin proteins* - Uncontrolled cell cycle progression due to **cyclin** dysregulation is a hallmark of cancer, but it is a result of accumulated **genetic mutations**. - This represents a cellular outcome of cancer development rather than the direct photochemical event initiated by UV radiation interacting with genomic DNA.

Question

What is the primary molecular mechanism by which UV light induces carcinogenesis?

Accepted Answer

Thymine dimers

Answer

Inhibition of TP53

Answer

Activation of NF-kappa beta signaling pathway

Answer

Upregulation of cyclin proteins

Molecular Pathology — MCQs

Molecular Pathology — MCQs

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