4.2 DNA And Protein Synthesis

Question 1

Describe translation

5 steps

Answer 1

1. mRNA leaves the nucleus via the nuclear pores
2. Ribosomes lock onto the mRNA.
3. The tRNA molecule’s anticodon bond to the specific complimentary codon. A second bonds in the same way
4. ATP is used to form peptide bonds between amino acids in close contact. The tRNA molecule moves away.
5. The process continues to form a polypeptide chain until the stop signal is reached

Question 2

Describe transcription

6 steps

Answer 2

1. DNA helicase breaks the hydrogen bonds, separating the strands and uncoiling it at that point
2. Exposed bases act as a template. RNA polymerase bonds to template strand
3. Complimentary free mRNA nucleotides join to the template strand
4. The mRNA is now a complimentary copy. DNA polymerase join the mRNA nucleotides together to form mRNA. This is called pre mRNA
5. Pre mRNA contains introns which must be spliced. Enzymes removes the introns and joins the extrons together
6. The hydrogens bonds between the complimentary bases in DNA and the DNA is wound back into a helix again

Question 3

Describe the differences between tRNA as mRNA

Answer 3

tRNA: 
Amino acid + codon active site
Smallest molecule
Clover shaped molecule
Chemically more stable than mRNA 
Contains H bonds

mRNA:
Contains codons
Larger than mRNA 
Single helix molecule
Less stable than tRNA 
No h bonds