Explain how mitotic recombination leads to the mosaiccondition termed twin spots.

A colleague e-mails you saying that she has identified an interesting chromosome variation at 21q13. In discussing this discovery with a friend who is not a cytogeneticist, explain how you would describe this location, defining each term in the chromosome address 21q13.

Figure 7.2 If a mutation occurs so that a fungus is no longer able to produce a minus mating type, will it still be able to reproduce? Figure 7.2 (a) In animals, sexually reproducing adults form haploid gametes from diploid germ cells. (b) Fungi, such as black bread mold (Rhizopus nigricans), have haploid-dominant life cycles. (c) Plants have a life cycle that alternates between a multicellular haploid organism and a multicellular diploid organism. (credit c fern: modification of work by Cory Zanker; credit c gametophyte: modification of work by Vlmastra/Wikimedia Commons)

What mechanisms are responsible for: (a) duplication of a chromosome segment; (b) generation of a Down syndrome individual; (c) a chromosome translocation; and (d) polyploidy?