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Flashcards in Transcription Deck (4)
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Q

Explain the term genetic code

A
  • the sequence of nucleotide bases on a gene provides a code with instructions for the construction of a polypeptide or protein
  • it is a triplet code (known as a codon) –> 3 bases code for 1 amino acid
  • there are 4 bases arranged in groups of 3 so the number of different triplet sequences is 64 (4x4x4)
  • it is a degenerate code –> some amino acids have more than 1 codon that codes for them
1
Q

What is a gene?

A
  • A gene is a length of DNA (sequence of nucleotide bases) that codes for one or more polypeptides
  • genes code for polypeptides such as enzymes
2
Q

Explain the process of DNA replication

A
  • DNA helicase breaks the hydrogen bonds between the bases
  • DNA polymerase binds, and activated free nucleotides will form hydrogen bonds with their complementary bases using the original strand as a template
  • DNA polymerase joins the sugar of one nucleotide with the phosphate of the next
  • DNA ligase seals the gaps in the sugar phosphate backbone
3
Q

Explain the process of transcription (how a nucleotide sequence codes for the amino acid sequence in a polypeptide)

A

• double helix uncoils in the region of the gene
• DNA helicase breaks the hydrogen bonds between the bases in the region of the gene
• - RNA polymerase binds to the template strand, activated RNA nucleotides will form hydrogen bonds with the complementary base pairs
-RNA polymerase moves in a 5’ to 3’ direction joining the phosphate of one nucleotide to C3 of the sugar on the next, forming an mRNA copy of the gene
• mRNA is the same as the coding strand (except it has U instead of T)
• mRNA is complementary to the template strand
• the mRNA then leaves the nucleus through the nuclear pore and travels to a ribosome