Sickle cell disease is caused by a:

a. change in one allele.

b. change in the size of a chromosome.

c. change in two proteins.

d. change in the number of chromosomes in a cell.

Which of the following is not considered an appendage of the skin? nails glands follicles none of the above

The negative change found inside the plasma membrane is created by potassium ions sodium ions hydrogen ions chlorine ions

Under the soviet system, the government a. controlled all forms of communication. b. allowed newspapers to print whatever they wanted. c. controlled editorials but not the reporting of news. d. encouraged access to a wide variety of news sources. select the best answer from the choices provided a b c d