DNA and protein synthesis

Question 1

What are the two important types of RNA used in protein synthesis?

Answer 1

• MRNA
• TRNA

Question 2

Define a Genome.

Answer 2

The complete set of genes in a cell

Question 3

Define a proteome.

Answer 3

The full range of proteins that a cell is able to produce

Question 4

What is the structure of MRNA? (4)

Answer 4

• A long, single strand
• A single helix
• Acts as a template for DNA, its base pairs are complementary to DNA
• These codons determine the amino acid sequence of the newly formed polypeptide

Question 5

What is the structure of TRNA?

Answer 5

• It is a small molecule made of 80 nucleotides
• it folds into a cloverleaf shape with one end being longer than the other, so an amino acid can easily join
• The opposite end is an anti-codon specific to the amino acid tRNA binds to

Question 6

What is step one of transcription?

Answer 6

• An enzyme binds to the DNA molecule and breaks the hydrogen bonding between complementary bases in DNA
• This unwinds the double helix and exposes the strand’s nucleotides
• One strand acts as a template and the other is the antisense strand

Question 7

What is step two of transcription?

Answer 7

• Free RNA nucleotides join to their complementary bases on the template strand.
• This means A - U and C - G

Question 8

What is step three of transcription?

Answer 8

• RNA polymerase attaches to the mRNA strand and it forms phosphodiester bonds between adjacent nucleotides
• As RNA polymerase joins the nucleotides on the mRNA strand, the DNA molecule rejoins
  -This means that it occurs 12 bases at a time to prevent damage to the DNA molecule

Question 9

What is step four of transcription?

Answer 9

• When RNA polymerase reaches a stop codon, it detaches

Question 10

What is the final step of transcription?

Answer 10

• The bases that correspond to introns are spliced and exons join together

Question 11

Why does splicing not occur in prokaryotes?

Answer 11

In prokaryotes, introns are very uncommon and do not require splicing

Question 12

Describe the process of translation?

Answer 12

• MRNA leaves the nuclear pore and binds to a ribosome
• A TRNA molecule will the complementary anticodon sequence moves to the ribosome and pairs with the codon on MRNA
• along with the anticodon, TRNA also carrys an amino acid
• Another