AP Biology Practice Exam 1 ❮ 281
- Gel electrophoresis question (10 points)
A. Electrophoresis experiment (maximum
5 points)
- Mentioning that smaller particles travel
faster. (1 point)
- Mentioning that the fragments of DNA
are placed into wells at the head of the gel
to begin their migration to the other side.
(1 point)
- Mentioning that the DNA migrates only
as electric current is passed through the gel.
(1 point)
- Mentioning that the DNA migrates from
negative charge to positive charge. (1 point)
- Mentioning that when DNA samples
from different individuals are cut with
restriction enzymes, they show variations
in the band patterns on gel electrophore-
sis known as restriction fragment length
polymorphisms(RFLPs). (1 point)
- Mentioning that DNA is specific to each
individual, and when it is mixed with
restriction enzymes, different combina-
tions of RFLPs will be obtained from
person to person. (1 point)
- Definition of a DNA fingerprint as the
combination of an individual’s RFLPs
inherited from each parent. (1 point)
- Mentioning that if an individual’s elec-
trophoresis pattern identically matches
that of the crime scene evidence, the DNA
has spoken and shown the individual to be
the perpetrator, since the probability of two
people having an identical set of RFLPs is
virtually non-existent. (1 point)
B. Paternity (maximum 5 points)
- Mentioning that DNA samples would need
to be taken from the disputed child and the
potential parents involved. (1 point)
- Definition of a restriction enzyme as an
enzyme that cuts DNA at a particular
sequence and creates open fragments of
DNA called “sticky ends.” (1 point)
- Mentioning that the DNA from all the
different individuals involved must be cut
by the same restriction enzyme(s) so that
the RFLPs created can be compared with
each other. (1 point)
- Mentioning that each sample of DNA
must be placed into a different well at the
top of the gel plate. (1 point)
- Mentioning that the DNA will migrate
from negative charge to positive charge,
once the current is applied, to create an
RFLP pattern specific for each individual—
this is a look at the DNA fingerprint of an
individual. (1 point)
- Mentioning that some sort of dye should
be added to the DNA samples that will
allow for proper viewing of the bands after
the current is disconnected. (1 point)
- Mentioning that one of the two DNA cuts
from the child’s fingerprint should match
up with one of the two DNA cuts from
the father’s fingerprint and one from the
mother’s fingerprint as well, because the
child inherits one chromosome of each
homologous pair from the mother and
one from the father. (1 point)
- Speciation question (here, you can obtain
4 points from a couple of the answers; if 4 points
are obtained for an answer, a maximum of
3 points can be obtained from each of the other
2 answers)
A. Geographic barriers (maximum 4 points)
- Mentioning how geographic barriers can
lead to reproductive isolation of members
from the same species. (1 ⁄ 2 point)
- Mentioning that if these geographically
separated species are moved into regions
that have different environments, natural
selection might favor different character-
istics from the same species in the differ-
ent environments. (1 point)
- Mentioning that this is an example of
allopatric speciation—interbreeding ceases
because some sort of barrier separates a
single population into two. (1 point)
- Definition of divergent evolution as the
evolution of two species farther apart from
each other as they are exposed to different
environmental challenges. (1 point)
❯ Free-Response Grading Outline
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