Scientific Discoveries 4. Watson and Crick made a successful model of DNA based on
Rosalind Franklin's X-ray studies. This indicated that DNA was
A. a 'triple helix with intertwined bases.
B. a double helix with bases outside the helix.
C. a double helix with bases inside the helix.
D. a single linear molecule of bases held together by
sugar-phosphate bonds.
Check Answer

Organisms are classified, or grouped into categories, based on similarities in their characteristics and/or evolutionary relationships. the study of how organisms are classified is known as

In a hypothetical breed of dogs, coat color is controlled by two genes. there are six different coat colors in this breed: black, brown, cream, gray, silver, and tan. consider the following crosses. cross 1: black females from a lineage of all black dogs are crossed with brown males from a lineage of all brown dogs. f1 males and females are all black. when f1 are intercrossed, f2 males and females are black or brown. cross 2: black females from a lineage of all black dogs are crossed with tan males from a lineage where all males are tan and all females are cream. f1 males are black, f1 females are gray. when f1 are intercrossed, f2 males and females are black, brown, gray, or tan. cross 3: silver females from a lineage where all females are silver and all males are gray are crossed with brown males from a lineage of all brown dogs. f1 males and females are all gray. when f1 are intercrossed, f2 males are black, brown, gray, or tan, f2 females are cream, gray, silver, or tan. select the correct statements regarding the mode of inheritance of the coat color genes. a) both genes are x-linked. b) both genes are autosomal. c) one of the genes modifies the expression of the other gene. d) each gene has an additive effect on the intensity of coat color. e) each gene independently specifies three colors. f) one of the genes is autosomal, and the other is x-linked.

Most animal cells membranes have proteins that pump ions out of the cell and potassium ions into the cell