USABO Open Exam Questions &
Answers (Grade A+)
Which statement is true about enzymes? Enzymes
A. Are made up of a base containing nitrogen, phosphate, and
ribose.
B. Have activity that is independent of temperature and pH.
C. Lose some or all of their normal activity when their 3-D structure
is disrupted.
D. Provide the activation energy needed to activate a reaction.
E. Work once only and then are destroyed. -
correct answer ✅C. Lose some or all of their normal activity when
their 3-D structure is disrupted.
You have a multicellular organism that reproduces asexually by
fission. When you excise a ~10,000 cell portion of its body, both the
original organism and the excised portion grow into fully formed,
healthy organisms. You take one of the offspring and repeat the
procedure for one hundred and twenty-three generations. Each
time, the resulting organisms are healthy. What must be true of the
nuclei of this species?
A. The cells contain plasmids.
B. The cells have multiple forms of DNA polymerase.
,USABO Open Exam Questions &
Answers (Grade A+)
C. The cells have the majority of their genome stored in circular
DNA.
D. The cells contain active telomerase.
E. The cells contain active fissonase. -
correct answer ✅D. The cells contain active telomerase.
Which of the following correctly describes how the lifespan of a
protein is regulated?
A. The part of the sequence coded for by the UTR tags it for
destruction.
B. Giant protein complexes called ubiquitins destroy proteins after
they have remained in the cell for a certain time.
C. Proteins are methylated over time; heavily methylated proteins
are destroyed by proteasomes.
D. Proteins are tagged with ubiquitins, which are recognized by
proteasomes; the proteasomes destroy the proteins.
E. Proteins tagged with methyl groups are destroyed by ubiquitins. -
correct answer ✅D. Proteins are tagged with ubiquitins, which are
recognized by proteasomes; the proteasomes destroy the proteins.
, USABO Open Exam Questions &
Answers (Grade A+)
Of the following amino acids, which is least likely to form strong
interactions with other amino acids that contribute to the tertiary
structure of a given protein?
A. Histidine
B. Glutamate
C. Cysteine
D. Glycine
E. Serine -
correct answer ✅D. Glycine
Thymine dimers arise when two adjacent thymine bases become
covalently linked. This interferes with normal DNA geometry and
will cause replication errors. Which of the following agents is the
primary cause of the thymine dimers?
A. Chemical mutagens
B. Beta emissions from radioactive decay
C. Gamma rays
D. X-rays
Answers (Grade A+)
Which statement is true about enzymes? Enzymes
A. Are made up of a base containing nitrogen, phosphate, and
ribose.
B. Have activity that is independent of temperature and pH.
C. Lose some or all of their normal activity when their 3-D structure
is disrupted.
D. Provide the activation energy needed to activate a reaction.
E. Work once only and then are destroyed. -
correct answer ✅C. Lose some or all of their normal activity when
their 3-D structure is disrupted.
You have a multicellular organism that reproduces asexually by
fission. When you excise a ~10,000 cell portion of its body, both the
original organism and the excised portion grow into fully formed,
healthy organisms. You take one of the offspring and repeat the
procedure for one hundred and twenty-three generations. Each
time, the resulting organisms are healthy. What must be true of the
nuclei of this species?
A. The cells contain plasmids.
B. The cells have multiple forms of DNA polymerase.
,USABO Open Exam Questions &
Answers (Grade A+)
C. The cells have the majority of their genome stored in circular
DNA.
D. The cells contain active telomerase.
E. The cells contain active fissonase. -
correct answer ✅D. The cells contain active telomerase.
Which of the following correctly describes how the lifespan of a
protein is regulated?
A. The part of the sequence coded for by the UTR tags it for
destruction.
B. Giant protein complexes called ubiquitins destroy proteins after
they have remained in the cell for a certain time.
C. Proteins are methylated over time; heavily methylated proteins
are destroyed by proteasomes.
D. Proteins are tagged with ubiquitins, which are recognized by
proteasomes; the proteasomes destroy the proteins.
E. Proteins tagged with methyl groups are destroyed by ubiquitins. -
correct answer ✅D. Proteins are tagged with ubiquitins, which are
recognized by proteasomes; the proteasomes destroy the proteins.
, USABO Open Exam Questions &
Answers (Grade A+)
Of the following amino acids, which is least likely to form strong
interactions with other amino acids that contribute to the tertiary
structure of a given protein?
A. Histidine
B. Glutamate
C. Cysteine
D. Glycine
E. Serine -
correct answer ✅D. Glycine
Thymine dimers arise when two adjacent thymine bases become
covalently linked. This interferes with normal DNA geometry and
will cause replication errors. Which of the following agents is the
primary cause of the thymine dimers?
A. Chemical mutagens
B. Beta emissions from radioactive decay
C. Gamma rays
D. X-rays
