RECOMBINATION IN SEXUAL ORGANISMS 



61 



in Figure 3.1, their bodies actually fuse together in a process called 

 syngamy, comparable to the fertilization of an egg by a sperm. This 

 results in the formation of a zygote which, in time, gives rise to four 

 gametes. Each of these divides asexually to produce large clones of 

 identical cells. Half of the clones are of mt'^ and half of mt~ mating 

 type. Under proper conditions, individual mt^ and mt~ cells may fuse 

 to form a zvgote once again, and the process repeats. 



Ratios-1 green : 1 yellow 



1 mating type +: 1 mating type - 



FIGURE 3.1. Diagram of the life cycle and the segregation of color in the unicellular 

 green alga, Chlamydomonas reinhardi. This microscopic fresh-water inhabitant swims 

 by using its whiplike flagellae. The normal green type contains chlorophyll ancJ can 

 live by photosynthesis. 



