DNA and Protein synthesis

Question 1

Two stages of protein synthesis

Answer 1

1. Transcription

• Production of mRNA from DNA
• Nucleus

2. Translation

• Production of polypeptides from the sequence of
  codons
  carried by mRNA
• Cytoplasm on ribosomes

Question 2

Describe process of transcription

Answer 2

In the Nucleus:
-DNA helicase breaks hydrogen bonds and unwinds double helix
-RNA nucleotides align next to their complementary bases on the template strand. Forming (temporary) hydrogen bonds - Uracil replaces thymine in RNA
-RNA polymerase joins adjacent nucleotides - condensation reaction
- Forming phosphodiester bonds
-When RNA polymerase reaches stop codon, mRNA detaches from DNA and leaves the nucleus through nuclear pores

Question 3

What’s splicing

Answer 3

In eukaryotes the pre-mRNA contains introns and exons. Splicing removes introns because they are the non-coding part of DNA while exon codes for an amino acid

Question 4

Describe the process of translation.

Answer 4

• Sequence of mRNA codons determines sequence of amino acids
• tRNAs carry specific amino acids, in relation to their anticodon
• At the ribosome, tRNA codon binds to mRNA codon
• tRNA anticodon complementary to mRNA codon
• Hydrogen bonds formed
• Two amino acids joined by condensation, forming a peptide bond
• Using energy from ATP
• tRNA detaches, ribosome moves along mRNA to next codon
• Continues until stop codon

Question 5

Importance of the enzyme

Answer 5

For DNA to be transcribed it first needs to be unwound so the enzyme DNA helicase is extremely important as it breaks hydrogen bonds between complementary base pairs. Without DNA helicase unwinding the DNA can be difficult as you cannot break the hydrogen bonds without damaging the DNA.

RNA polymerase is crucial for transcription as it joins adjacent nucleotides together. For example Uracil binds with Adenine and then it forms a phosphodiester bond to form the mRNA sequence.

Transcription and Translation is important as it allows for the formation of polypeptide chains. These are very important in forming proteins and some form enzymes. Without transcription and translation there would be no proteins in the body let alone enzymes which means no DNA helicase produced for the breakdown of hydrogen bonds so it makes DNA replication and transcription less effective and slower