Gene s controls the sharpness of spines in a type of cactus. cactuses with the dominant allele, s, have sharp spines, whereas homozygous recessive ss cactuses have dull spines. at the same time, a second gene, n, determines whether or not cactuses have spines. homozygous recessive nn cactuses have no spines at all.
if doubly heterozygous ssnn cactuses were allowed to self-pollinate, the f2 would segregate in which of the following ratios?
a) 3 sharp-spined: 1 spineless
b) 1 sharp-spined: 2 dull-spined: 1 spineless
c) 1 sharp-spined: 1 dull-spined: 1 spineless
d) 1 sharp-spined: 1 dull-spined
e) 9 sharp-spined: 3 dull-spined: 4 spineless

The answer is E) 9 sharp-spined:3 dull-spined:4 spineless.

It is known that the in dihybrid cross (a cross between two different traits), the phenotypic ratio between the offspring in the F2 generation is 9:3:3:1:
9 - individuals with both dominant traits (SSNN),
3 - individuals with the first dominant trait and the second recessive trait (SSnn),
3 - individuals with the first recessive trait and the first recessive trait (ssNN),
1 - individual with both recessive traits (ssnn).

According to this, there will be 9 sharp-spined cactuses (SSNN), 3 dull-spined cactuses (ssNN), and 4 spineless cactuses (3 cactuses with SSnn genotype and 1 cactus with ssnn genotype).

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