3.2 Chromosomes

3.2 Chromosomes

1. Nature of Science

   • Autoradiography was used to establish the length of DNA molecules in chromosomes
     • Cairns' technique
       • Comparison of genome size
         • T2 phage
         • Escherichia coli
         • Drosophila melanogaster
         • Homo sapiens
         • Paris japonica
       • Aim 6
         • Staining root tips
       • Aim 7
         • Use of databases to identify gene loci and protein products of genes

2. The number of chromosomes is a characteristic feature of members of a species

   • Prokaryotes
     • Naked Circular DNA
     • Plasmid
   • Eukaryotes
     • Linear DNA with histone proteins
       • Nucleus
         • Diploid (2n)
           • Have pairs of homologous chromosomes
             • Homologous chromosomes carry the same sequence of genes but no necessarily the same alleles of those genes
           • Comparison of 2n chromosome numbers
             • Pan troglodytes
             • Oryza sativa
             • Parascaris equorum
             • Homo sapiens
             • Canis familiaris
         • Haploid (n)
           • One chromosome of each pair

3. Karyogram vs Karyotype

   • A karyogram shows the chromosomes of an organism in homologous pairs of decreasing length
     • Sex chromosomes vs Autosomal chromosomes
     • Deduce sex and diagnose Down syndrome

4. International-mindedness

   • Sequencing of the rice genome involved cooperation between biologists in 10 countries