Solved by a verified expert:Biology 2112: Lab 11 Genetics
Problems Fall 2015
These problems are the final lab exercise
and are worth 15 points. Similar
problems will appear on the final lab exam.
To receive complete credit for a question, you must document you answers
with the appropriate work; a Punnett Square, showing the gametes, etc. that
leads you to your answer. Use separate
paper for your answers. No credit will
be given for an answer that lacks supporting argument. Show all your work in a neat and orderly
fashion. Making the lab instructor
search will reduce your allotted points. Turn problems into your lab instructor
on the day of your lab at the final lab after the Fall break. If you put them
in a mailbox, the problems must be date stamped by the office. But a missing problem
set is not our responsibility. Late penalty doubled to 40% per day.
1.
What genetically distinct gametes can be produced by organisms with the
following genotypes?
RrGg rrGG RrGG rrgg
2.
What progeny would you expect
in the following crosses? Choose and
recombine the gametes. You do not need to have a complete Punnett Square
showing repeated possibilities.
RrGg
x RrGG Rrgg
x rrGG RrGG x Rrgg RrGg x rrgg
3.
In Tomatoes, the allele for red
fruit is dominant over the allele for yellow
fruit. If a plant that is homozygous
for red fruit is crossed with a plant
with yellow fruit –
a) what is/are the genotype(s) and the phenotype(s) of the fruit
produced in the F1 generation?
b) what is/are the genotype(s) and the phenotype(s) of the fruit
produced in the F2 generation?
c) what is the phenotypic ratio of the F2 fruit?
4. A
plant with red flowers is crossed with a plant with white flowers. All the F1 plants produced red
flowers. When the F1plants
are allowed to self-pollinate, they produce 623 plants with red flowers and 198
plants with white flowers. What are the
genotypes of the P and F1 generations?
5.
In Tomatoes, the allele for red
fruit is dominant over the allele for yellow
fruit. The allele for tall plants is dominant over the allele
for short plants. Find the genotypes and phenotypes of the F1
and F2 generations and the phenotypic ratio of a cross between a
homozygous dominant in both genes and a homozygous recessive in both genes. The
homozygous individuals are the Parental generation.
6. The probability that a baby will be a
boy is ½ as is the probability that a baby will be a girl. Explain this fact by explaining the mechanism
of meiosis in the production of gametes and the process of fertilization. If a family has 4 boys and 3 girls, what is
the probability that the next child will be a girl?
7. Duchenne Muscular Dystrophy is caused by
a relatively rare X-linked recessive allele (mutation). Use XMfor a
normal gene and Xm for the mutated allele. It causes progressive
muscle degeneration and usually leads to death by age 20. An unaffected man marries a normal woman
whose brother was affected by this disorder.
Neither set of parents of the couple have muscular dystrophy. What is
the probability their first child will be a son who is affected with the
disease, how about a daughter? Explain,
using a Punnett square(s), how you arrived at your answer.
8. A
skin cell from a human female undergoes mitosis. For an unknown reason, the centromeres of one of the two number 4 chromosomes fail to separate. Describe the resultant chromosome number of the two daughter cells. Indicate the genetic make-up each cell. Suppose this happened to a single cell in reproductive tissue undergoing meiosis II (the
cell went through Meiosis I normally). What would be the chromosome number of the resulting cells from this cell? Provide a diagram to illustrate this. If instead of a problem with Meiosis II, the
problem was with homologous chromosomes not separating in Meiosis I, what would
be the complement of chromosomes for each of the resultant gametes produced? Provide a diagram to illustrate this. For all scenarios assume that the cells
finish mitosis and meiosis even if not viable due to an abnormal chromosome
count.
9. A
rare condition known as adermatoglyphia leads to such smooth fingertips that
the individual has no fingerprints. It has been dubbed the “immigration
delay disease” because sufferers have such a hard time entering foreign
countries. Recently the cause has been traced to a point mutation in the very
first nucleotide of an intron. The
allele with this mutation (F) is dominant to the wild type allele (f). The condition also leads to less hand sweat
than the average person and researchers think that the gene might help skin
cells fold over one another early in fetal development. A woman with adermatoglyphia marries a man with
adermatoglyphia (assume both are heterozygous).
Why might it be difficult to calculate the probability they will have a
child with fingerprints. Consider the genotypes and phenotypes of all potential
children and the possible contribution of the gene to early fetal
development? (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3155166/
– Amer. J. Hum. Genet. 89, 302–307, 2011.
You do not need to consult this reference but you should read a commentary on
it http://news.sciencemag.org/sciencenow/2011/08/the-mystery-of-the-missing-fingerprints.html).
Note that this problem is as much to teach you about the ambiguities of
some problems as statistics.
)
10.
As a consequence of independent assortment of chromosomes during meiosis
(the biological explanation for Mendel’s 2nd law), each mature
gamete from an individual differs greatly in the combination of chromosomes
inherited from the parents of that individual.
However, random assortment of chromosomes is not the sole source of
reassorting genetic information during meiosis.
Explain why this could be so using the following data. On the same chromosome there are two genes
for finger length and hair texture, with long fingers (F) & curly hair
dominant (H) over short fingers (f) and straight hair (h). The parents of a man had the following
genotypes FFHH and ffhh. His wife shows
the homozygous recessive phenotype for both traits, short fingers with straight
hair. One of their children has the long
finger and straight hair phenotype.
Diagram the homologous chromosomes, the gametes, any relevant events
before and during gamete production and fertilization to support your argument
explaining how this child could have this particular phenotype.
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