Inversion of DNA sequences within chromosomes is a common process in evolution. The following gene arrangements in a particular chromosome are found in four different species: First sequence: ABCDEF
Second sequence: ABFEDC
Third sequence: FEDABC
Fourth sequence: ADEFBC

Assuming that the arrangement in the first sequence is the ancestor/reference arrangement, in what evolutionary order did the four species arise, such that the fewest number of inversions occur between each species (place the first sequence as the earliest species in your ordering)?

The correct answer is "Fist sequence; Fourth sequence; Second sequence; Third sequence".

Explanation:

Inversion of DNA is a process that often occurs during evolution of chromosomes. It occurs when the breakage of a chromosome in two places, results in the reinsertion of a DNA but in a reversed fashion. The evolutionary order of predecessors of inversion of DNA can be established by looking on the number of nucleotides that are different in the sequences of DNA. In this case, the first sequence is the ancestor and it haves the sequence "ABCDEF". The second in the evolutionary order is the fourth sequence since it originates from the first sequence only by changing the "BC" nucleotides to the end of the sequence "ADEFBC". The third in the evolutionary order is the second sequence since it still starts in AB, but has the other four nucleotides different: "ABFEDC". The last in the evolutionary order is the third sequence, which is completely different and reversed respect to the first sequence: "FEDABC".

it would be c. xylem.

white blood cells or wbc s are mainly 2 types-

1.agranulocytes

2.granulocytes

the monocytes or macrophages of agranulocytes , dendritic cells which are accessory leucocytes, and b cells which is one type of lymphocytes   identify the antigens present on the pathogen's surface. these three cells are called antigen presenting cells(apc) which are phagocytes and destroy the antigens by secreting antitoxins. besides this leukocyte is always plays vital role in the immunity of the body.