Download Exam 2 Key

BioSci 110, Fall 08
Exam 2
1. __________ is the cell division process that results in the production of ___________
a. mitosis; 2 gametes
b. meiosis; 2 gametes
c. meiosis; 2 somatic (body) cells
d. mitosis; 4 somatic (body) cells
e. *meiosis; 4 gametes
2. A 21-year old male MSU student is sunbathing in Fort Lauderdale during Spring Break. As a result of
excessive UV radiation, a mutation (change in base sequence) occurs in the Y chromosome in a skin cell on
his shoulder. The mutated chromosome:
a. will be passed on to all of his children
b. will be passed on to all of his sons, but none of his daughters
c. will be passed on to all of his sons, and half of his daughters
d. will be passed on to half his sons, but none of his daughters
e. *will not be passed on to any of his children
3. The locus for a gene of interest is marked on the chromosome figures below. At meiosis 1, a crossing-over
event occurs in which the long-arms are exchanged between homologous chromosomes. For which
chromosome(s) will the crossing-over have no effect on the resulting genotypes of the gametes?
a.*
b.
c.
d. B and C
e. All of the above will result in changed genotypes of gametes
4. Hemophilia is a genetic disorder that results in excessive bleeding due to absence of an important clotting
factor. Hemophilia is inherited as an X-linked recessive allele. If a woman with hemophilia marries a normal
man, what outcome do you expect for their children?
a*
b
c
d
e
Girls
100% girls are carriers
100% girls are normal
50% girls are carriers; 50% are hemophiliacs
50% girls are carriers; 50% are normal
50% girls are carrier; 50% are hemophiliacs
Boys
100% are hemophiliacs
100% are hemophiliacs
50% are normal, 50% are hemophiliacs
50% are normal, 50% are hemophiliacs
50% are carriers, 50% are hemophiliacs
(Questions 5 and 6). Squash color is controlled by the interaction of two epistatic genes. White squash (W) is
dominant to colored squash (w). If this gene is homozygous recessive, a second gene (Y) controls squash
color where yellow (Y) is dominant to green (y).
5. Which genotype results in yellow squash?
a. WWyy
b. WwYY
c. WwYy
d. *wwYY
e. wwyy
6. At market, yellow squash sells better than white or green. If a farmer knows that she has seeds with the
genotype WwYy, what would be the best genotype to cross her seeds with to maximize yellow squash
production (and profit)?
a. WWyy
b. *wwYY
c. wwyy
d. WWYY
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BioSci 110, Fall 08
Exam 2
(Questions 7-10) The Canary Islands are seven islands just west of the African continent. The islands
gradually became colonized with life: plants, lizards, birds, etc. Three different species of lizards found on the
islands are similar to one species found on the African continent (Thorpe and Brown 1989). Because of this,
scientists assume that the lizards traveled from Africa to the Canary Islands by floating on tree trunks washed
out to sea.
7. On one of the islands, a well-established population of lizards is made up of hundreds of individual lizards.
The lizards in the lizard population are likely to be:
a. indistinguishable, since there is a lot of interbreeding in isolated populations.
b. the same genotypically, but display differences in their phenotypes.
c. the same phenotypically, but display differences in their genotypes.
d. *similar, yet have some significant differences in their genotypes and phenotypes.
8. Which statement best describes how traits in lizards will be inherited by offspring?
a. When parent lizards learn to catch particular insects, their offspring can inherit their specific insectcatching skills.
b. When parent lizards develop stronger claws through repeated use in catching insects, their offspring can
inherit their stronger-claw trait.
c. When parent lizards’ claws are underdeveloped because easy food sources are available, their offspring
can inherit their weakened claws.
d. *When a parent lizard is born with an extra finger on its claws, its offspring can inherit six-fingered claws.
9. According to the theory of natural selection, where did the variations in body size in the three species of
lizards most likely come from?
a. The lizards needed to change in order to survive, so beneficial new traits developed.
b. The lizards wanted to become different in size, so beneficial new traits gradually appeared in the
population.
c. *Random genetic changes and sexual recombination both created new variations.
d. The island environment caused genetic changes in the lizards.
10. Fitness is a term often used by biologists to explain the evolutionary success of certain organisms. Below
are descriptions of four fictional female lizards. Which lizard might a biologist consider to be the “most fit”?
Body length
Offspring
surviving to
adulthood
Age at death
Comments
Lizard A
20 cm
*Lizard B
12 cm
Lizard C
10 cm
Lizard D
15 cm
19
28
22
26
4 years
Lizard A is very
healthy, strong,
and clever
5 years
Lizard B has
mated with many
lizards
4 years
Lizard C is darkcolored
and very quick
6 years
Lizard D has the
largest territory of
all the lizards
(Questions 11 and 12). In cats, ear shape and hair length are independently
controlled by genes carried on separate chromosomes (they are not linked).
Short hair (H) is dominant to long hair (h), and curled ears (E) are dominant to
straight ears (e).
“Moses” (from Exam 1) has short hair and straight ears. Moses’ mother has
long hair and curled ears.
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BioSci 110, Fall 08
NAME:_____ KEY ______________________
Exam 2
PID: _________
Group#/Name: _______________
11. (16 pts) In the panels below, draw cells from Moses at the phases indicated. Draw the correct number of
cells and chromosomes in each panel and label:
• alleles (B, b, E, e)
• homologous chromosomes (1 pt)
• centromere (1 pt)
• sister chromatids (1 pt)
a. (2 pts) What is Moses’ genotype? Hhee (1 pt Hh; 1 pt ee)
b. (3 pts) Moses’ cell at G2 (after DNA replication)
A correct representation includes:
•
•
•
4 chromosomes correctly labeled with alleles
chromosomes are in the replicated state,
sisters are identical
correct genotype (from above) is represented
d. (3 pts) Moses’ cell/s at metaphase of meiosis 2.
•
•
•
2 cells
each cell has 1 member from the homologous
pair in “c” (ploidy is reduced)
chromosomes are in the replicated state and
aligned by centromeres at the equatorial plane
c. (2 pts) Moses’ cell/s at metaphase of meiosis 1.
•
•
chromosomes are in the replicated state, and
lined up in pairs at the equatorial plane
homologous chromosomes are opposite one
another at the equatorial plane
e. (3 pts) Products of meiosis of Moses’ cell
•
•
•
4 cells
each cell has 1 sister from the replicated
chromosomes in “d” – thus, the chromosomes
are unreplicated in the gametes
gametes are haploid – 1 member from each
homologous pair, following from division of
each M2 cell
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BioSci 110, Fall 08
NAME:_____ KEY ______________________
Exam 2
PID: _________
Group#/Name: _______________
12. (16 pts) Moses’ owner decides to breed him with “Lena”. Lena is homozygous dominant for both traits.
___ a. (2 pts) What is Lena’s genotype? HHEE Rewrite Moses’ genotype (from 16a): Hhee
___ b. (2 pts) What is Lena’s phenotype? Short hair (1pt), curled ears (1pt)
___ c. (2 pts) What genotypes of gametes (eggs) is Lena capable of producing? HE only
___ d. (2 pts) What genotypes of gametes (sperm) is Moses capable of producing? He, he
___ e. (4 pts) Draw the Punnett Square for the cross between Moses and Lena.
HE
He
HHEe
he
HhEe
___ e. (2 pts) Predict the genotypic ratio for kittens resulting from this cross (note: you must include both the
numerical value AND the resultant genotypes for full credit).
50% HHEe; 50% HhEe (also, 1:1, etc.)
1pt – genotypes; 1pt - ratios
___ f. (2 pts) Predict the phenotypic ratio for the kittens resulting from this cross (note: you must include both
the numerical value AND the resultant phenotypes for full credit).
100% of kittens will be short-haired with curled ears
1pt – genotypes; 1pt - ratios
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BioSci 110, Fall 08
NAME:______ KEY _____________________
Exam 2
PID: _________
Group#/Name: _______________
13. (8 pts) A gene found in Brazil nuts, codes for 2S albumin, a protein rich in the essential amino acid
methionine. In an effort to improve the nutritional quality of soybeans, researchers isolated the 2S albumin gene
from Brazil nuts and inserted this gene into the soybean genome. 2S albumin can cause allergic reaction in
many individuals with nut allergies. If an individual is allergic to the protein in Brazil nuts and is not allergic to
soybeans, would you expect them to be allergic to the transgenic soybean?
____ a. (3 pts) YES / NO. BRIEFLY explain. Yes. The 2S albumin gene will code for exactly the same
protein whether in the Brazil nut or in the transgenic soybean. If an individual is allergic to the protein
when it is found naturally in the Brazil nut, he/she will be allergic to the protein when the gene is
expressed in the transgenic soybean.
____ b. (5 pts) In the space below, draw a simple model to show how the above GMO would be made.
Models will be diverse in their appearance. Models must represent the following information:
1pt –Brazil nut contains 2S albumin gene
1pt – the 2S albumin gene is isolated from the source (may include reference to restriction enzymes,
etc.)
1pt – plasmid (or other vector, such as virus or particle gun) is used to move the gene into the soybean
1pt – the gene is integrated into the genome of the soybean
1pt – the gene is copied to other cells in soybean by the process of mitotic cell division
19. (10 pts) In a box-and-arrow model, concepts are structures that are linked by behaviors. Behaviors are
short phrases or linking words that clearly and concisely describe the relationship between structures.
Behaviors are generally active, and therefore tend to be verbs, while structures are concepts or nouns.
____ a. (8 pts) In the space below, construct a box and arrow model that demonstrates your understanding of
the following concepts: gene, allele, DNA molecule, chromosome, protein, phenotype, mutation, and
genetic variation. In your model, the concepts provided should be represented as structures – you may use
them more than once if it helps you build your model.
Each concept listed above is represented accurately in association with a correct behavior.
2 pts awarded for correctly representing the associations indicated below, with correct/accurate
descriptive words:
- chromosome-DNA – DNA is represented as being equivalent to or a component of a chromosome;
hierarchical organization is represented correctly
- gene-allele – alleles are indicated as alternative versions of genes; new alleles arise as the result of
mutations in existing genes
- allele-variation – the consequence of mutations in existing alleles is that new alleles arise. Mutation is
the origin of all variation and the ultimate source of genetic variation in a population
- protein-phenotype – alternative alleles code for the production of different proteins that are expressed
as different phenotypes. Individuals in a population differ in their phenotypes owing to the activity of
proteins encoded by different alleles.
____ b. (2 pts) In a sentence or less, what is the function of your model?
Variable – must be consistent with information represented in model. Anticipated functions include:
origin of genetic variation, etc.
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BioSci 110, Fall 08
Exam 2
NAME:___ KEY________________________
PID: _________
Group#/Name: _______________
14. (10 pts) In an on-line Evolution Pre-test, you were asked to use your current understanding of evolution by
natural selection to explain the changes that occurred in the tree and animal (above). A complete explanation
of natural selection would include 5 fundamental principles of evolution indicated in the left column of the table
below. In the right column, explain how each concept is represented in (or relevant to) the scenario above.
Genetic Variation
Origin of Variation
Inheritance
Fitness
Population Change
Individuals (animals and plants) in the population differ from one another at any
given time. Genetic differences account for the phenotypic variation we see for
height of dinosaurs and plants.
Random mutations in existing alleles result in different sequences of bases, thus
new alleles. Random mutations resulted in alleles for taller heights in both
dinosaurs and plants.
Genetic information is passed from parent to offspring through the gametes.
New alleles that conferred greater height were passed on to offspring of the
dinosaurs and plants.
Individuals differ in their ability to reproduce. Initially, plants that were taller were
able to escape being eaten by dinosaurs, thus produced more offspring than
short plants. Later, dinosaurs that were taller were able to reach the taller plants,
acquire more resources, and reproduce more than short dinosaurs who couldn’t
reach the food.
Alleles for height conferred the greatest fitness advantage for plants (early) and
dinosaurs (later). Be definition, the fittest individuals reproduce the most – they
will pass their alleles on to their offspring. Over time, the alleles for height will
become more abundant in the population (because tall individuals are
reproducing the most), and the population will become taller on average.
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