8.7 - Protein Synthesis: Transcription

Question 1

Splicing in eukaryotes:

Answer 1

• both introns and exons are transcribed into the initial mRNA transcript (pre-mRNA
• pre-mRNA undergoers RNA splicing - introns are removed and exons are joined together
• produces mature mRNA consists of exon sequences
• mature mRNA then travels out of the nucleus for translation

Question 2

differences in transcription in prokaryotes and eukaryotes:

Answer 2

1. in prokaryotes, DNA is produced from transcription without splicing
2. in eukaryotes, pre-mRNA is spliced after transcription to remove introns before being transported to the cytoplasm

Question 3

What happens in transcription?

Answer 3

1. Transcription begins with the RNA polymerase enzyme binding to DNA.
2. The hydrogen bonds between the DNA bases break, and the two strands of the double helix separate.
3. The antisense strand acts as the template for mRNA synthesis.
4. Free RNA nucleotides align with the DNA template through complementary base pairing.
5. In the RNA molecule, uracil pairs with adenine, while adenine pairs with thymine, and cytosine pairs with guanine.
6. RNA polymerase catalyses the formation of phosphodiester bonds between adjacent RNA nucleotides.
7. A complementary mRNA strand is formed, carrying the same base sequence as the DNA sense strand.
8. The process ends when RNA polymerase reaches a stop codon, detaches from DNA and terminates transcription.
9. mRNA is released, detaches from DNA, and DNA rewinds into its double helix structure.

Question 4

Where does translation then occur for eukaryotic cells after transcription?

Answer 4

exits the nucleus and enters the cytoplasm where translation occurs

Question 5

Where does transcription take place within eukaryotic cells?

Answer 5

takes place within the nucleus