TRANSCRIPTION AND TRANSLATION

Question 1

What is transcription

Answer 1

The name of the process in which a copy of DNA is made
Copy is known as mRNA
Process occurs in the nucleus of the cell

Question 2

mRNA

Answer 2

sequence of mRNA is determined by the sequence of bases on a length of DNA in transcription
Acts as a template for protein synthesis
Leaves the nucleus through pores and works with ribosomes
Chemically unstable meaning polypeptide synthesis will not occur indefinitely and so can be controlled

Question 3

Describe the process of transcription

Answer 3

1. DNA helicase breaks hydrogen bonds between base pairs exposing them
2. Only one DNA strand acts as a template
3. RNA nucleotides attract to exposed bases
   4.:attraction according to base pairing rule
4. RNA polymerase joines the RNA nucleotides together to form pre mRNA
5. Pre mRNA is spliced to remove introns forming mRNA

Question 4

What is splicing of pre mRNA

Answer 4

Only occurs in eukaryotic cells
Prokaryotic cells dont have introns
Splicing = removing introns and joins exons together (order depends on the protein being made)
Mutations may result in faulty splicing leading to non functional proteins e.g. seen in Alzheimer’s disease

Question 5

Describe the process of translation

Answer 5

1. mRNA leaves the nucleus through nuclear pores
2. Enters the ribosome
3. tRNA Molecules bring amino acids to the ribosome
4. A specific tRNA molecule exists for a specific amino acid
5. Anticodon of tRNA complementary to the codon on mRNA
6. Peptide bonds form between adjacent amino acids
7. tRNA detaches and leaves to collect another amino acid
8. Ribosome moves along mRNA

Question 6

tRNA compared to mRNA

Answer 6

has base pairing mRNA doesnt
tRNA cloverleaf shape mRNA linear
tRNA has amino acid bonding site mRNA doesnt
tRNA is shorter