When a Xenopus oocyte is stimulated with the hormone progesterone, it enters meiosis and arrests at ______, awaiting fertilization by a sperm.
a. prophase I
b. metaphase I
c. prophase II
d. metaphase II
Ans: d. metaphase II
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Which molecule catalyzes covalent bond formation between fragments of DNA.
A. helicase. B. ligase. C. polymerase. D. primase. E. nuclease.
A trait unique to embryonic stem cells that makes them useful for generating knockout animals is that they
A) are totipotent. B) can be grown in culture. C) have been isolated from mice. D) are extremely well characterized at the molecular level.
In order to be detected by a T cell, the class I major histocompatibility (MHC) molecule of infected cells must go through the process of
A) antigen presentation. B) complement activation. C) phagocytosis. D) antibody binding. E) perforin incorporation.
The ____ is responsible for the separation of the chromosomes during the ____ of mitosis
a. cell wall; anaphase b. mitotic spindle; interphase c. mitotic spindle; anaphase d. kinetochore; prophase e. centromere; telophase