USABO OPEN EXAM NEWEST 2025 ACTUAL EXAM
COMPLETE ACTUAL QUESTIONS AND CORRECT
DETAILED ANSWERS (VERIFIED ANSWERS)||
USABO OPEN EXAM NEWEST 2025 |ALREADY
GRADED 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. - 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.
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. - 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. - D. Proteins
are tagged with ubiquitins, which are recognized by proteasomes; the proteasomes
destroy the proteins.
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 - 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
E. UV rays - E. UV rays
Which of the following oligonucleotides would have the highest melting point
when paired with the proper complementary strand?
A. 5'-AAAAAAAA-3'
B. 5'-ATGCATGC-3'
C. 5'-CGCGCGCG-3'
D. 5'-TTTTGGGG-3'
E. 5'-TATATATA-3' - C. 5'-CGCGCGCG-3'
Which of the following is a way in which the cell increases gene expression in the
nucleus?
A. Acetylation of histone tails
B. DNA methylation
C. Locating a gene within heterochromatin
D. Dephosphorylating DNA
E. Alternative splicing - A. Acetylation of histone tails
Which of the following statements about cellular ultrastructure is FALSE?
, A. Nonmotile eukaryotic cilia are composed of 9 doublets of microtubules in a
ring, with no microtubules in the center ('9+0').
B. Bacterial flagella are composed of 9 doublets of microtubules in a ring, with
two microtubules in the center ('9+2').
C. Motile eukaryotic cilia are composed of 9 doublets of microtubules in a ring,
with two microtubules in the center ('9+2').
D. Centrioles are composed of nine triplets of microtubules arranged in a ring.
E. The basal bodies of eukaryotic flagella are composed of nine triplets of
microtubules arranged in a ring. - B. Bacterial flagella are composed of 9 doublets
of microtubules in a ring, with two microtubules in the center ('9+2').
Which of the following chemicals or groups of chemicals is not a major
determinant of flower color?
A. Flavonols
B. Carotenoids
C. Cyanidin
D. Phytoalexins
E. Betacyanins - D. Phytoalexins
Which of the following is not a characteristic of cycads?
A. Secondary growth from a vascular cambium
B. Fruit
C. True leaves
D. Insect pollination
E. Presence of neurotoxins and carcinogens in plant tissues - B. Fruit
COMPLETE ACTUAL QUESTIONS AND CORRECT
DETAILED ANSWERS (VERIFIED ANSWERS)||
USABO OPEN EXAM NEWEST 2025 |ALREADY
GRADED 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. - 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.
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. - 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. - D. Proteins
are tagged with ubiquitins, which are recognized by proteasomes; the proteasomes
destroy the proteins.
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 - 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
E. UV rays - E. UV rays
Which of the following oligonucleotides would have the highest melting point
when paired with the proper complementary strand?
A. 5'-AAAAAAAA-3'
B. 5'-ATGCATGC-3'
C. 5'-CGCGCGCG-3'
D. 5'-TTTTGGGG-3'
E. 5'-TATATATA-3' - C. 5'-CGCGCGCG-3'
Which of the following is a way in which the cell increases gene expression in the
nucleus?
A. Acetylation of histone tails
B. DNA methylation
C. Locating a gene within heterochromatin
D. Dephosphorylating DNA
E. Alternative splicing - A. Acetylation of histone tails
Which of the following statements about cellular ultrastructure is FALSE?
, A. Nonmotile eukaryotic cilia are composed of 9 doublets of microtubules in a
ring, with no microtubules in the center ('9+0').
B. Bacterial flagella are composed of 9 doublets of microtubules in a ring, with
two microtubules in the center ('9+2').
C. Motile eukaryotic cilia are composed of 9 doublets of microtubules in a ring,
with two microtubules in the center ('9+2').
D. Centrioles are composed of nine triplets of microtubules arranged in a ring.
E. The basal bodies of eukaryotic flagella are composed of nine triplets of
microtubules arranged in a ring. - B. Bacterial flagella are composed of 9 doublets
of microtubules in a ring, with two microtubules in the center ('9+2').
Which of the following chemicals or groups of chemicals is not a major
determinant of flower color?
A. Flavonols
B. Carotenoids
C. Cyanidin
D. Phytoalexins
E. Betacyanins - D. Phytoalexins
Which of the following is not a characteristic of cycads?
A. Secondary growth from a vascular cambium
B. Fruit
C. True leaves
D. Insect pollination
E. Presence of neurotoxins and carcinogens in plant tissues - B. Fruit
