In considering the cross yyrr x yyrr, the genotype ratio is yyrr: 2yyrr: 2yyrr: 4yyrr: yyrr: 2yyrr: yyrr: yyrr: yyrr. true fals

False.

In a dihybrid cross, the expected ratio of genotypes is 1:2:1:2:4:2:1:2:1.
In this example the ratio is 1:2:2:4:1:2:1:1:1. So, this ratio is false. It is expected 1YYRR : 2YYRr : 1Yyrr : 2YyRr : 4YYrr : 2YyRR : 1yyRR : 2yyRr : 1yyrr.

The truman doctrine was an american foreign policy whose stated purpose was to counter soviet geopolitical expansion during the cold war. it was announced to congress by president harry s. truman on march 12, 1947, and further developed on july 12, 1948, when he pledged to contain threats to greece and turkey