[Unit 8.4/5] | Transcription, Splicing & Translation

Question 1

What is the basic outline of protein synthesis?

Answer 1

• DNA provides a sequence of bases as instructions.

• Transcription occurs to produce pre-mRNA

• pre-mRNA is spliced to form mRNA.

• mRNA is used as a template for tRNA to bind to during translation, where the tRNA’s amino acids are linked to form polypeptides.

Question 2

Describe the process of transcription.

Answer 2

1. Enzyme breaks down the hydrogen bonds in a section of DNA.
2. DNA strands unzip, allowing one strand to act as a template.
3. Free RNA nucleotides bind to complementary bases on the template.

• Adenine pairs with Uracil instead of Thymine.

4. RNA polymerase acts to bind adjacent nucleotides in a condensation reaction.
   (The DNA strand closes up as the RNA nucleotides bind to one another.)

• Phosphodiester bonds form between nucleotides.

5. A termination sequence is reached, signalling that the production of pre-mRNA is finished.
6. Pre mRNA is spliced to form mRNA.

Question 3

What is splicing?

Answer 3

The removal of non-coding introns from a DNA/RNA molecule.

Question 4

Describe the process of translation.

Answer 4

1. mRNA binds to a ribosome.
2. tRNA anticodons bind to complementary mRNA codons.
3. tRNA carries a specific amino acid.
4. Ribosome moves along mRNA…

• Producing peptide bonds between the amino acids using ATP.

5. As amino acids bind, their tRNA molecules are released from the ribosome.

Question 7

How is a protein formed from a polypeptide chain?

Answer 7

• Coiled / folded