Final answer:
The parts of a DNA molecule amongst the options are the promoter, silencer, and enhancer. The poly A tail is associated with mRNA; the sigma subunit and transcription factors are proteins that interact with DNA but are not part of its structure.
Step-by-step explanation:
Within a DNA molecule, several elements play crucial roles in the process of transcription and gene expression. From the options provided, the following are parts of a DNA molecule:
- Promoter (a): This is a specific sequence of DNA nucleotides where RNA polymerase binds to initiate transcription.
- Silencer (b): DNA sequences that can bind transcription regulatory proteins (repressors) to inhibit the expression of a gene.
- Enhancer (f): DNA sequences that can increase the rate of transcription when regulatory proteins (activators) bind to them.
On the other hand, elements like the poly A tail, sigma subunit, and transcription factors are not parts of the DNA molecule:
- The poly A tail is added post-transcriptionally to the 3' end of mRNA.
- The sigma subunit is a component of the prokaryotic RNA polymerase that confers specificity to transcription.
- Transcription factors are proteins that regulate the transcription of genes by binding to DNA but are not part of the DNA molecule itself.