Regulatory segments of DNA that function to increase transcription levels in eukaryotes are called:

• A. promoters.
• B. silencers.
• C. enhancers.
• D. transcriptional start sites.
• E. activators.

Answer: (C)

Verified step by step guidance

1. Understand the role of regulatory DNA segments in gene expression. These segments can either increase or decrease the transcription of genes.
2. Identify the function of each option: Promoters are DNA sequences where RNA polymerase binds to initiate transcription. Silencers are sequences that can repress transcription. Enhancers are sequences that increase the transcription levels of associated genes. Transcriptional start sites are the locations where transcription begins. Activators are proteins that bind to enhancers to increase transcription.
3. Focus on the term 'increase transcription levels' in the problem statement. This indicates a positive regulatory role.
4. Recognize that enhancers are the regulatory DNA segments specifically known for increasing transcription levels by interacting with activators and other transcription factors.
5. Conclude that the correct answer is 'enhancers' as they are the DNA segments that function to increase transcription levels in eukaryotes.