BIOL 133 QUIZ 3 | COMPREHENSIVE BIOLOGY STUDY GUIDE, PRACTICE
QUESTIONS & ANSWERS 2026/2027
True or False. Epigenetic changes result in changes to an organism's DNA sequence. - ANS ✔✔This is
false because epigenetic changes result in changes to chemical groups associated with DNA that alter
gene expression.
In 1940, the frequency of the A allele in a large population is 0.4. In 2012, the frequency of the A allele in
this population is 0.2. This is most likely an example of - ANS ✔✔Natural selection
A point mutation that results in a codon that specifies the same amino acid as the non-mutated codon is
called a - ANS ✔✔silent mutation
A frame shift mutation - ANS ✔✔creates a protein with a new sequence of amino acids
Mutations are typically bad for the individuals who inherit them but may be good for a population
overall. This is because mutations - ANS ✔✔are the ultimate source of genetic variation.
In a population of 1000 people, the frequency of people who cannot taste PTC is 0.36 (tasting PTC is
caused by a dominant allele). If this population is in Hardy-Weinberg equilibrium, how many people are
expected to be heterozygous for the alleles involved in tasting PTC? - ANS ✔✔480
Attached ears is an autosomal recessive trait in humans. Assume that there are 90 people with attached
ears in a population of 1000. How many individuals would be expected to be homozygous dominant? -
ANS ✔✔490
Down's syndrome (trisomy 21) is relatively common in the US but trisomy 18 (known as Edward's
syndrome) is rare and the symptoms of Edward's syndrome are more extreme than those of Down's
syndrome. Which of the following is the best explanation for this? - ANS ✔✔Chromosome 18 has more
genes that are important to development than chromosome 21.
The term "_______________" refers to a change in genotype while the term "_______________" refers
to a change in phenotype. - ANS ✔✔mutation ; mutant
An aneuploidy results from a ____________________. If it occurs during ________________, all of the
gametes will have an abnormal chromosome number - ANS ✔✔nondisjunction ; meiosis I
In a population, the frequency of the allele for Huntington's disease, a dominant condition, is 0.01. What
percentage of the population is expected to NOT have Huntington's? - ANS ✔✔98%
In laboratory studies using genetically identical rats, rat pups that have been nurtured by their mothers
grow up to be nurturing mothers. Those that have been neglected grow up to be neglectful mothers.
This difference in maternal behavior is heritable but there is no genetic difference between the mothers.
This is an example of - ANS ✔✔epigenetic changes resulting from different environments.
QUESTIONS & ANSWERS 2026/2027
True or False. Epigenetic changes result in changes to an organism's DNA sequence. - ANS ✔✔This is
false because epigenetic changes result in changes to chemical groups associated with DNA that alter
gene expression.
In 1940, the frequency of the A allele in a large population is 0.4. In 2012, the frequency of the A allele in
this population is 0.2. This is most likely an example of - ANS ✔✔Natural selection
A point mutation that results in a codon that specifies the same amino acid as the non-mutated codon is
called a - ANS ✔✔silent mutation
A frame shift mutation - ANS ✔✔creates a protein with a new sequence of amino acids
Mutations are typically bad for the individuals who inherit them but may be good for a population
overall. This is because mutations - ANS ✔✔are the ultimate source of genetic variation.
In a population of 1000 people, the frequency of people who cannot taste PTC is 0.36 (tasting PTC is
caused by a dominant allele). If this population is in Hardy-Weinberg equilibrium, how many people are
expected to be heterozygous for the alleles involved in tasting PTC? - ANS ✔✔480
Attached ears is an autosomal recessive trait in humans. Assume that there are 90 people with attached
ears in a population of 1000. How many individuals would be expected to be homozygous dominant? -
ANS ✔✔490
Down's syndrome (trisomy 21) is relatively common in the US but trisomy 18 (known as Edward's
syndrome) is rare and the symptoms of Edward's syndrome are more extreme than those of Down's
syndrome. Which of the following is the best explanation for this? - ANS ✔✔Chromosome 18 has more
genes that are important to development than chromosome 21.
The term "_______________" refers to a change in genotype while the term "_______________" refers
to a change in phenotype. - ANS ✔✔mutation ; mutant
An aneuploidy results from a ____________________. If it occurs during ________________, all of the
gametes will have an abnormal chromosome number - ANS ✔✔nondisjunction ; meiosis I
In a population, the frequency of the allele for Huntington's disease, a dominant condition, is 0.01. What
percentage of the population is expected to NOT have Huntington's? - ANS ✔✔98%
In laboratory studies using genetically identical rats, rat pups that have been nurtured by their mothers
grow up to be nurturing mothers. Those that have been neglected grow up to be neglectful mothers.
This difference in maternal behavior is heritable but there is no genetic difference between the mothers.
This is an example of - ANS ✔✔epigenetic changes resulting from different environments.
