Question

Transcription: From DNA to RNA

1. Define a gene.

2. How does RNA differ from DNA?

3. Briefly describe the process of transcription.

4. Describe the process of transcription as it occurs in prokaryotes.

5. What is the role of the promoter?

6. Describe the process of transcription as it occurs in eukaryotes.

7. What is the role of the transcription factors? A mutation exists in transcription factors that causes them to bind slightly downstream of the TATA box, causing them to cover the first 3 nucleotides of a gene. RNA polymerase can still transcribe the gene to mRNA, but it misses the first 3 nucleotides. How would this impact translation?

8. What is the role of kinase and phosphatase in eukaryotic transcription?

9. How does RNA polymerase know which strand of the DNA to transcribe? What would happen if it chose the wrong strand?

10. Why does translation in prokaryotes begin before transcription is complete?

11. What must occur in eukaryotes before translation can begin?

12. How are the ends of the mRNA modified in eukaryotes?

13. What are introns and exons?

14. Describe the process of RNA splicing.

15. What is the role of alternative splicing in evolution?

16. Compare and contrast transcription in prokaryotes and eukaryotes.

Answer 1

1) A gene is a sequence of DNA or RNA. It contains the information about the function of molecules in a molecule. It can also be understood as the basic physical and functional unit of heredity. Genes, which are made up of DNA, act as instructions to make molecules called proteins.

2) DNA is a long chain of deoxyriboses and phosphate backbone. It has four bases - adenine, guanine, cytosine and thymine. While, RNA is a chain of ribose and phosphate backbone. It has four bases - adenine, guanine, cytosine, and uracil.

The structure of RNA is different from DNA in three ways:

1. It forms a single strand sugar-phosphate chain.
2. The sugar in its nucleotides is ribose.
3. The base thymine is replaced by the base uracil.

3) Transcription is the process of RNA synthesis. It is controlled by the interaction of promoters and enhancers. The process of transcription involves four steps Initiation, Promoter escape, Elongation and Termination. In other words, the transcription is the process of mRNA synthesis from an RNA molecule.

4) Prokaryotes are mostly single-celled organisms and lack membrane-bound nuclei and other organelles. Transcription in prokaryotes requires the DNA double helix to partially unwind in the region of RNA synthesis. Prokaryotes use the same RNA polymerase to transcribe all genes.