Features of the Genetic code

• What are the three key features of the genetic code for AQA biology?

  Degenerate, universal, non-overlapping
• The start codon in DNA is TAC
• The start codon codes for the amino acid methionine.
• What is the role of the stop codon in translation?

  Terminates translation
• There are 20 different amino acids coded for by the genetic code.
• The genetic code uses four DNA bases: guanine, cytosine, thymine, and adenine.
• What mathematical formula proves that the genetic code must use three bases to code for at least 20 amino acids?

  $4^{3} =$$64$
• The genetic code is degenerate because most amino acids are coded for by more than one triplet of bases.
• Match the amino acid with a coding triplet:

  Tyrosine ↔️ ATA

  Alanine ↔️ GCC

  Serine ↔️ AGC
• What is a silent mutation, and why does it occur in a degenerate genetic code?

  Change in base, no effect
• The genetic code is universal, meaning the same triplets code for the same amino acids in almost every living thing.
• Why is the universality of the genetic code important in genetic engineering?

  Allows gene transfer between species
• The genetic code is non-overlapping because each base is only part of one triplet that codes for an amino acid.
• What is the advantage of the non-overlapping nature of the genetic code?

  Minimizes mutation impact
• What are introns, and where are they found in DNA?

  Non-coding DNA in eukaryotes
• Exons are sequences of DNA that code for amino acids.
• Match the term with its definition:

  Genome ↔️ Complete set of DNA

  Proteome ↔️ Full range of proteins
• What is the key difference between the genome and the proteome of a cell?

  Genome is fixed, proteome changes
• The genome of all organisms is approximately the same size.

  False
• How many DNA base pairs are in the human genome approximately?

  Three billion