Astrand of dna in a skin cell contains the bases:
a-t-g-c-c-a-t-c-g-g-t-a
after the cell is exposed to ultraviolet light, the strand contains the bases:
a-t-g-g-c-c-a-t-c-g-g-t-a
which statement describes the result of this exposure?
(1)a new base has been inserted.
(2)a base has been deleted.
(3)one base has been substituted for another.
(4)there have been no changes in the bases.

of those who start drinking before they're 15 will develop alcohol dependence

answer : haversian

[explanation: -(compact bone is organized as parallel columns, known as haversian systems, which run lengthwise down the axis of long bones. these columns are composed of lamellae, concentric rings of bone, surrounding a central channel, or haversian canal, that contains the nerves, blood vessels, and lymphatic system of the bone)]