topic 4

• What is the main topic of AQA A Level Biology Topic 4?

  Genetic information, variation & relationships
• What is a similarity between DNA in eukaryotic and prokaryotic cells?

  Nucleotide structure is identical
• How are adjacent nucleotides in DNA joined?

  By phosphodiester bonds
• What type of DNA do mitochondria and chloroplasts have?

  Similar structure to prokaryotic DNA
• What is a key difference between eukaryotic and prokaryotic DNA?

  Eukaryotic DNA is longer
• How is eukaryotic DNA structured compared to prokaryotic DNA?

  Eukaryotic DNA is linear, prokaryotic is circular
• What proteins are associated with eukaryotic DNA?

  Histone proteins
• What do eukaryotic genes contain that prokaryotic genes do not?

  Introns

  
• What is a chromosome?

  Long, linear DNA with histone proteins

  
• Where are chromosomes located in eukaryotic cells?

  In the nucleus
• What is a gene?

  A sequence of DNA bases coding for proteins
• What does a locus refer to in genetics?

  Fixed position of a gene on DNA
• What is the nature of the genetic code?

  It is a triplet code
• What does a triplet code consist of?

  A sequence of 3 DNA bases
• What does it mean that the genetic code is universal?

  Same triplets code for amino acids in all organisms
• What does it mean that the genetic code is non-overlapping?

  Each base is part of only one triplet
• What does it mean that the genetic code is degenerate?

  An amino acid can be coded by multiple triplets

  
• What are non-coding base sequences?

  DNA that does not code for polypeptides
• Where are non-coding base sequences found?

  Between genes and within genes (introns)
• What are introns?

  Base sequences that don’t code for amino acids
• What are exons?

  Base sequences coding for amino acid sequences
• What are the key differences between introns and exons?

  • Introns: Non-coding sequences in eukaryotic cells
  • Exons: Coding sequences for amino acids
• What are the similarities and differences between eukaryotic and prokaryotic DNA?

  Similarities:

  • Identical nucleotide structure
  • Joined by phosphodiester bonds
  • Mitochondrial/chloroplast DNA similar to prokaryotic

  
  

  Differences:

  • Eukaryotic DNA is longer and linear
  • Eukaryotic DNA associated with histones
  • Eukaryotic DNA contains introns