Genetic information, variation and relationships

• What is the shape and association of DNA molecules in prokaryotic cells?

  Short, circular and not associated with proteins
• How are DNA molecules structured in the nucleus of eukaryotic cells?

  Very long, linear and associated with proteins called histones
• What do DNA molecules and their associated proteins form in eukaryotic cells?

  A chromosome
• What type of DNA do mitochondria and chloroplasts contain?

  Short, circular and not associated with protein
• What is a gene?

  A base sequence of DNA that codes for the amino acid sequence of a polypeptide or a functional RNA
• What are the two main functions of a gene?

  • Codes for the amino acid sequence of a polypeptide
  • Codes for a functional RNA (including ribosomal RNA and tRNAs)
• What is the fixed position of a gene on a DNA molecule called?

  A locus
• What does a sequence of three DNA bases, known as a triplet, code for?

  A specific amino acid
• What are the characteristics of the genetic code?

  • Universal
  • Non-overlapping
  • Degenerate
• What does it mean that much of the nuclear DNA in eukaryotes does not code for polypeptides?

  It includes non-coding multiple repeats of base sequences between genes
• What are non-coding sequences between genes called?

  Non-coding multiple repeats of base sequences
• What are exons?

  Sequences within a gene that code for amino acid sequences
• How are exons and introns related within a gene?

  Exons are separated by one or more non-coding sequences called introns