8.2 - DNA and chromosomes

• What are DNA molecules like in prokaryotic cells ?


  They’re short, circular and not associated with proteins
• Do prokaryotic cells have chromosomes ?


  No
• What are the DNA molecules in eukaryotic cells nuclei like ?


  They’re very long, linear and and are associated with with proteins called histones
• What 2 things form a chromosome ?


  A DNA molecule and its associated proteins
• What is the DNA is mitochondria and chloroplasts, in eukaryotic cells, like ?


  It‘s short, circular and not associated with proteins, just like the DNA in prokaryotic cells
• What’s each single thread of a chromosome called and why ?


  A chromatid as DNA has already replicated to give 2 identical DNA molecules
• What’s the DNA in chromosomes held by ?


  Histones
• What are homologous chromosomes ?


  2 chromosomes that carry the same genes but may not have the same alleles (half from mum, half from dad)