In order to infect a cell, a virus must
A. have a special protein on its surface that can interact with a protein on the surface of the host cell.
B. produce a special extension of its cytoplasm when it comes into contact with the appropriate host cell.
C. actively burrow through the cell wall or cell membrane of the host cell to reach the cell's nucleus.
D. inject its protein into the cell while the nucleic acid remains attached to the host cell surface.
Answer: A
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One function of sphincter muscles is to
a. control the passage of food through the GI tract b. secrete digestive juices into the GI tract c. control peristalsis d. trigger hormone release e. grind large food particles
Compare chicken, frog, and mammalian ova as to size and the amount of yolk present.
Ova Size Amount of Yolk Chicken Frog Mammalian
The hormone secreted by the blastocyst that is found in the mother's urine and is the basis for most pregnancy tests.
A) Human chorionic gonadotropin
B) Zygote
C) Chorion
D) Morula
E) Folic acid
F) Fertilization
G) Blastocyst
H) Parturition
I) Cleavage
J) Ovulation
K) Placenta
L) Implantation
A man inherited a chromosome with a deletion that removes a tumor-suppressor gene. The protein encoded by this gene normally functions in DNA damage repair. Which series of events would be most likely to lead to cancer?
A) Loss-of-heterozygosity of the tumor-suppressor gene followed by driver mutations in two different proto-oncogenes B) A loss-of-function mutation in a proto-oncogene followed by a gain-of function mutation in a tumor-suppressor gene C) Loss-of-heterozygosity of the tumor-suppressor gene followed by passenger mutations in several genes of unknown function D) A gain-of-function mutation in a proto-oncogene followed by a chromosomal duplication of a region including a tumor-suppressor gene that functions the G1-to-S checkpoint