Which sequence is the best target for damage by UV radiation: AGGCAA, CTTTGA, or GUAAAU? Why aren’t all bacteria killed when they are exposed to sunlight?

Verified step by step guidance

1. Identify the type of nucleic acid each sequence represents: DNA or RNA.
2. Recognize that UV radiation primarily causes damage by forming thymine dimers in DNA.
3. Determine which sequences contain thymine (T) bases, as these are susceptible to UV-induced dimer formation.
4. Compare the sequences: AGGCAA, CTTTGA, and GUAAAU, and identify which has the most thymine bases.
5. Understand that not all bacteria are killed by sunlight because they have repair mechanisms, such as photoreactivation and nucleotide excision repair, to fix UV-induced damage.

Key Concepts

DNA Structure and UV Damage

DNA is composed of sequences of nucleotides, which can be damaged by UV radiation. UV light causes the formation of pyrimidine dimers, primarily thymine dimers, leading to distortions in the DNA structure. This damage can disrupt replication and transcription, ultimately affecting cell viability. Understanding the specific sequences that are more susceptible to UV damage is crucial for identifying the best target.

Bacterial DNA Repair Mechanisms

Bacteria possess various DNA repair mechanisms that allow them to survive UV-induced damage. These include photoreactivation, where light activates enzymes to repair dimers, and nucleotide excision repair, which removes damaged sections of DNA. These repair systems enable many bacteria to withstand exposure to sunlight, explaining why not all are killed despite UV radiation.

Bacterial Diversity and Resistance

Different bacterial species exhibit varying levels of resistance to UV radiation due to genetic diversity and environmental adaptations. Some bacteria have evolved protective mechanisms, such as pigmentation or biofilm formation, which can shield them from UV exposure. This diversity in survival strategies contributes to the resilience of bacterial populations in natural settings, even under sunlight.