BIO 184: Quiz 4 (10 pts.) Name:


1.       On the picture of the spread of human chromosomes (below), circle homologous chromosome pair 1 and explain how you identified them.


Also identify the sex of the individual from which these chromosomes came and explain how you determined the sex.



2.       The watermelon, Citrullus lanatus, has 11 different chromosomes or a diploid chromosome number of 2n = 22. To create seedless watermelons, diploid plants are treated with colchicine, such that they become tetraploid. Then crosses are made using gametes produced by the diploid plants and gametes produced by the tetraploid plant. The resulting offspring are triploid and produce defective seeds because normal meiosis requires pairs of homologs.


         How many chromosomes should be present in the sporophyte tissue of the triploid watermelons?




         From what you have learned about the activity of colchicine (aka colcemid), explain how colchicine would aid in the creation of tetraploid plants.









3.       How many chromosomes would a human with a trisomy have?


Name a human chromosomal abnormality due to trisomy and describe three major symptoms associated with it. Explain how the syndromes associated with aneuploidies show that each chromosome carries many genes.





4.       The G-banded chromosomes below illustrate a translocation in humans, called t(3;4)(p21;q34). The "p" and "q" refer to chromosome arms, and the numbers refer to the bands along the arms. The centromeres (lined up on the horizontal line) are considered zero points and numbers get larger as you approach the tips of the chromosomes.


         Define the term translocation.






         Closely examine the patterns of bands on the normal and rearranged chromosomes. On the diagram above, clearly indicate what parts of the normal chromosomes were rearranged in the translocation.



5.       Before DNA sequences were available, the relationship between humans and other primates was supported by similarities between their chromosomes. For example, the G-banding pattern of chromosome 4 of humans and chimpanzees is shown below.


It has been suggested that one can be derived from the other by the occurrence of an inversion.


      Define the term inversion.




      Then clearly indicate on the diagram above the segment most likely involved in the inversion.