All of the following nucleotide bases are pyrimidines except

A. cytosine.
B. cytosine and thymine.
C. thymine.
D. adenine.
E. uracil.


Answer: D

Biology & Microbiology

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In eukaryotic cells, we sometimes find reverse transcriptase activity, even though the cells are not infected with virus. This activity can be attributed to

A) the presence of transposons integrating into polymerase genes. B) the presence of viroids. C) the presence of retrotransposons. D) infection with small bacteria known as mycoplasmas. E) a novel prion infection.

Biology & Microbiology

Which of the following crosses will NOT produce offspring with the recessive phenotype? Select all that apply.A) TT × TtB) Tt × TtC) TT × TTD) Tt × ttE) tt × tt

What will be an ideal response?

Biology & Microbiology

p53 is often referred to as the “guardian of the genome” by cancer research scientists. According to the diagram, which action by p53 explains its reputation?



a. Mutated p53 results in cancer.
b. p53 can trigger apoptosis.
c. p53 arrests the cell cycle if there is DNA damage.
d. p53 monitors the supply of oxygen in the environment.

Biology & Microbiology

Which of the following are types of symbioses? Check all that apply.  

_____  Batesian mimicry _____  commensalism _____  predation _____  parasitism _____  mutualism _____  Müllerian mimicry

Biology & Microbiology