Section 8.4 Study Guide: DNA Transcription
Vocabulary
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Central dogma
RNA
Transcription
RNA polymerase
Messenger RNA (mRNA)
Ribosomal RNA (rRNA)
Transfer RNA (tRNA)
Review Questions
1. From the diagram below, explain what the central dogma is and how it works. What is happening at
each step?
The central dogma says that protein synthesis is only one way. In your cells it
goes from DNA to RNA (through transcription in the nucleus) to Protein (via the process of
translation – in the cytoplasm).
2. What is transcription?
Transcription converts a gene (a specific sequence of DNA nucleotides) into a single-stranded RNA
molecule called messenger RNA (mRNA).
3. Compare and contrast DNA and RNA. How are they different (name at least 3 differences)?
DNA contains deoxyribose, RNA containes ribose
DNA has the base Thymine while Uracil replaces thymine in RNA.
DNA is double-stranded (double helix) while RNA is single-stranded.
4. What enzyme helps a cell to make a strand of RNA?
RNA Polymerase
5. Summarize the three key steps of transcription.
RNA polymerase and other enzymes assemble at the start of a gene (a sequence of DNA
nucleotides) and begin to unwind the DNA. Using one strand of the DNA as a template, RNA
polymerase strings nucleotides together to make a complementary strand of RNA. The RNA
strand detaches from the DNA as it is being transcribed. Once the RNA strand detaches, the DNA
zips back together.
6. Write the basic function for mRNA, rRNA, and tRNA.
mRNA – intermediate message (transcribed from DNA) that is translated to form a protein.
rRNA – creates ribosomes with the help of other proteins.
tRNA – brings amino acids from the cytoplasm to a ribosome to help make the growing protein.
7. How does the name of each type of RNA tell what it does?
mRNA is a form of the DNA code that tells the cell what type of protein to make. rRNA is a key
component of ribosomes. tRNA transfers, or carries, amino acids from the cytoplasm to the
ribosome.
8. List two ways that the processes of transcription and replication are similar.
Both occur within the nucleus of eukaryotic cells; are catalyzed by large enzymes; involve
unwinding of the DNA double helix; involve complementary base pairing of the DNA strand; and
are highly regulated by the cell.
9. List two ways that the end results of transcription and replication differ.
Replication occurs only once during each round of the cell cycle and makes a double-stranded
copy of all of the DNA in a cell. Transcription on the other hand occurs repeatedly throughout the
cell cycle to make proteins, rRNAs, and tRNAs as needed by the cell. Transcription makes a singlestranded complement of only a particular DNA sequence.