Mendel's Law 



43 



Fig. 3 shows a somatic cell with the diploid niuiiber 

 of chromosomes. Tii the fomiation of gametes, this 

 number is reduced to the haploid number, which is in 

 this case two. The diagram shows that the reduction 

 division separates (segregates) the two chromosomes 

 carrying the determiner for tallness, so that each gamete 

 contains one. This occurs for the other characters as 

 well as for that of tallness. From the tall plant, therefore, 



Dwarf Parent 



Fig. 3. — Diagram illustrating behavior of chromosomes in Mexdel's 

 cross of tall and dwarf peas. Large rectangular figures, nuclei of zygotes 

 or mature individuals; large circles, gametes; snij^l circles within zygotes 

 and gametes, chromosomes; letters on chromosomes, determiners {T, 

 tallness; Z>, dwarfness). 



all the gametes will contain the detenniner for t;\llness, 

 and from a dwarf plant all of the gametes will contain 

 the determiner for dwarfness. When these two indi- 

 viduals are crossed, the zygote will contain both deter- 

 miners, and these two determiners will be transmitted 

 together in the succeeding cell generations. The indi\id- 

 ual developed from such a zygote will of course be tall, 

 but at the same time it will be carr}ing a recessive deter- 

 miner for dwarfness, and this fact will be shown by its 

 behavior in breeding. The result of inbreeding such hy- 



