USABO Open Exam Questions with Complete Solutions 100% Solved| Grade A+
A. Both populations will end up at approximately B=0.80, b=0.20.
B. The island and continent populations will stabilize with an allele frequency of B=0.50, b=0.50.
C. Black mice will move to fixation in both populations, because the B allele is dominant.
D. Both populations will end up at B=0.20, b=0.80.
E. The continent' A. Both populations will end up at approximately B=0.80, b=0.20.
Chromosome segregation is an important step in both mitosis and meiosis. Determine if the
following statements are true or false.
A. Abnormalities in sex chromosome segregation in humans are always fatal.
B. In most mammals and birds, males have XY sex chromosomes.
C. Down's Syndrome is often caused by a chromosome segregation error.
D. It is not uncommon for plants to have more than 2 copies of each chromosome. A. False
B. False
C. True
D. True
Which of the following is a genetic variation of Klinefelter's Syndrome?
A. XXX.
B. XO.
C. XXO.
D. XXXO.
E. XXYY. E. XXYY.
,In the mucus of the intestinal epithelium, you observe an interesting relationship between
mucus-dwelling bacteria and various bacteriophage. Bacteria continually evolve mechanisms to
avoid phage attack, and phage continually evolve methods to get around the bacterial
defenses. This is an example of...
A. Red Queen dynamics.
B. Mutualism.
C. Convergent evolution.
D. Commensalism.
E. Ammensalism. A. Red Queen dynamics.
A dog breeder wants to breed dogs with thick, shaggy coats. Assume that the thick-coat trait is
recessive. Two dogs, both with thick coats and of the same breed, are mated, but all the
puppies are short-haired. From this you can conclude that...
A. Having two copies of the thick coat allele is lethal.
B. There is another gene controlling the expression of the thick-coat genes by epistasis.
C. Dogs of this breed with thick coats are never true breeding for the thick coat trait.
D. There are two thick-coat genes at separate loci; each parent is double recessive for a
different one, and the genes complement each other in the puppies. A. False
B. False
C. False
D. True
A pea plant X dihybrid for flower color and height is crossed with a pea plant Y true breeding for
flower color and height. Pea plant X is tall and has purple flowers while pea plant Y is short and
has white flowers. Given that the genes are on separate chromosomes, tall is dominant to short
and purple is dominant to white, find the phenotypic ratios of the offspring.
, A. 1 tall purple: 1 short purple: 1 tall white: 1 short white.
B. 9 tall purple: 3 short purple: 3 tall white: 1 short white.
C. 9 tall purple: 3 short purple: 4 short white.
D. 9 tall purple: 7 short white.
E. 9 tall purple: 4 short white. A. 1 tall purple: 1 short purple: 1 tall white: 1 short white.
Which of the following statements apply to viral capsids?
A. Viral capsomeres display self-assembly and depending on the virus can form helical or
icosahedral capsids.
B. Each viral capsid is formed from identical capsomeres, which allows for self-assembly.
C. Viral capsomeres are derived from host proteins and undergo virus-specific posttranslational
modifications
D. Viral mRNA transcripts are translated by eukaryotic ribosomes to form capsid proteins. A.
True
B. False
C. False
D. True
If a yellow-coat colored mouse is crossed with a gray-coat colored mouse, what phenotypic
frequency is expected among their progeny?
A. 1/2 yellow, 1/2 gray
B. 3/4 gray, 1/4 yellow
C. 3/4 yellow, 1/4 gray
D. 7/16 gray, 9/16 yellow
E. 9/16 yellow, 7/16 gray A. 1/2 yellow, 1/2 gray
A. Both populations will end up at approximately B=0.80, b=0.20.
B. The island and continent populations will stabilize with an allele frequency of B=0.50, b=0.50.
C. Black mice will move to fixation in both populations, because the B allele is dominant.
D. Both populations will end up at B=0.20, b=0.80.
E. The continent' A. Both populations will end up at approximately B=0.80, b=0.20.
Chromosome segregation is an important step in both mitosis and meiosis. Determine if the
following statements are true or false.
A. Abnormalities in sex chromosome segregation in humans are always fatal.
B. In most mammals and birds, males have XY sex chromosomes.
C. Down's Syndrome is often caused by a chromosome segregation error.
D. It is not uncommon for plants to have more than 2 copies of each chromosome. A. False
B. False
C. True
D. True
Which of the following is a genetic variation of Klinefelter's Syndrome?
A. XXX.
B. XO.
C. XXO.
D. XXXO.
E. XXYY. E. XXYY.
,In the mucus of the intestinal epithelium, you observe an interesting relationship between
mucus-dwelling bacteria and various bacteriophage. Bacteria continually evolve mechanisms to
avoid phage attack, and phage continually evolve methods to get around the bacterial
defenses. This is an example of...
A. Red Queen dynamics.
B. Mutualism.
C. Convergent evolution.
D. Commensalism.
E. Ammensalism. A. Red Queen dynamics.
A dog breeder wants to breed dogs with thick, shaggy coats. Assume that the thick-coat trait is
recessive. Two dogs, both with thick coats and of the same breed, are mated, but all the
puppies are short-haired. From this you can conclude that...
A. Having two copies of the thick coat allele is lethal.
B. There is another gene controlling the expression of the thick-coat genes by epistasis.
C. Dogs of this breed with thick coats are never true breeding for the thick coat trait.
D. There are two thick-coat genes at separate loci; each parent is double recessive for a
different one, and the genes complement each other in the puppies. A. False
B. False
C. False
D. True
A pea plant X dihybrid for flower color and height is crossed with a pea plant Y true breeding for
flower color and height. Pea plant X is tall and has purple flowers while pea plant Y is short and
has white flowers. Given that the genes are on separate chromosomes, tall is dominant to short
and purple is dominant to white, find the phenotypic ratios of the offspring.
, A. 1 tall purple: 1 short purple: 1 tall white: 1 short white.
B. 9 tall purple: 3 short purple: 3 tall white: 1 short white.
C. 9 tall purple: 3 short purple: 4 short white.
D. 9 tall purple: 7 short white.
E. 9 tall purple: 4 short white. A. 1 tall purple: 1 short purple: 1 tall white: 1 short white.
Which of the following statements apply to viral capsids?
A. Viral capsomeres display self-assembly and depending on the virus can form helical or
icosahedral capsids.
B. Each viral capsid is formed from identical capsomeres, which allows for self-assembly.
C. Viral capsomeres are derived from host proteins and undergo virus-specific posttranslational
modifications
D. Viral mRNA transcripts are translated by eukaryotic ribosomes to form capsid proteins. A.
True
B. False
C. False
D. True
If a yellow-coat colored mouse is crossed with a gray-coat colored mouse, what phenotypic
frequency is expected among their progeny?
A. 1/2 yellow, 1/2 gray
B. 3/4 gray, 1/4 yellow
C. 3/4 yellow, 1/4 gray
D. 7/16 gray, 9/16 yellow
E. 9/16 yellow, 7/16 gray A. 1/2 yellow, 1/2 gray
