Genes a and b are 10 map units apart, b and c are 20 map units apart, and a and c are 30 map units apart. If a triple heterozygote is testcrossed, among 1,000 progeny, how many are expected to result from double crossovers if there is no interference? а. 10;
b. 20;
c. can't be determined
d. 30;
e. 60;

20 ( B )

Explanation:

Given data:

a and b are 10 map units apart

b and c are 20 map units apart

a and c = 30 map units apart

condition ; Triple heterozygote testcrossed

number of progeny = 1000

Determine the number of double crossover result

P( crossover between a and b ) = 10/100 = 0.1

P( crossover between b and c ) = 20/100 = 0.2

p( double crossover ) = 0.1 * 0.2 = 0.02

hence number of double crossovers = number of progeny * 0.02

                                                              = 1000 * 0.02 = 20

answer and explanation;

volcanic rocks are igneous rocks which form from lava, molten rock which has been thrust out of a volcano onto the surface of a rocky body such as an asteroid, planet, or dwarf planet.  

plutonic rocks are igneous rocks which form from subterranean chambers of molten rock or magma. plutonic rocks make up the base of continental crust as well as oceanic crust. their slow rate of formation causes them to be coarse grained since there is plenty of time for large crystals to form before the magma solidifies into rock.

the textural difference is that plutonic rocks are more coarse grained than volcanic rocks. plutonic rocks are coarse grained while volcanic are fine grained ; glassey or fragmental. since fine and coarse are adjectives the decision as to whether a rock is fine or coarse grained is generally made on the bases of whether or not the individual crystals can be seen in most if the rock.