Solved by a verified expert:Four basic genetics problems
Practice problems
1. You’re working in a lab that studies a particularly
gruesome parasite from the Amazon that infests people’s ear canals while they
sleep. This parasite has a diploid number of 12 chromosomes in its somatic
cells, consisting of 6 homologous pairs (i.e. 6 maternal and 6 paternal
chromosomes). Another student in your lab tells you that only one-fourth of the
gametes produced by meiosis in this parasite will have all of it’s chromosomes
from either maternal or paternal origin (i.e. all the chromosomes from dad or
all the chromosomes from mom). Assume that meiosis in this parasite works just
like meiosis in organisms we’ve talked about in class and explain whether you
think the student is correct.
2. A diploid somatic cell from a rat has a total of 42
chromosomes (2n = 42). Answer the following questions:
A. How many different chromosomes (i.e. carrying different
genes) does the rat have?
B. How many molecules of DNA are in the nucleus of a somatic
rat cell in G1?
C. How many telomeres are in the nucleus of a somatic rat
cell in G1?
D. How many molecules of DNA are in the nucleus of a somatic
rat cell in G2?
E. How many telomeres are in the nucleus of a somatic rat
cell in G2?
F. How many DNA molecules are in the nucleus of a rat cell
in metaphase of mitosis?
G. How many chromosomes are in the nucleus of a rat cell in
metaphase of mitosis?
H. How many DNA molecules are in the nucleus of a rat cell
in metaphase I of meiosis?
I. How many chromosomes are in the nucleus of a rat cell in
metaphase I of meiosis?
J. How many DNA molecules are in the nucleus of a rat cell
in metaphase II of meiosis?
K. How many chromosomes are in the nucleus of a rat cell in
metaphase II of meiosis?
3. For a particular plant, red flowers (A) are dominant over
yellow flowers (a). An initial cross was made between a plant that was
true-breeding for red flowers, and another plant true-breeding for yellow
flowers. F1 progeny, all having red flowers, were allowed to form seeds, which
were then planted to generate F2 progeny. Pollen from all the resulting F2
plants was pooled and used to fertilize true-breeding yellow plants. What
proportion of the progeny resulting from this cross would be expected to have
yellow flowers?
4. You learn that a Mars lander has retrieved a bacterial
sample from the polar ice caps. You obtain a sample of the bacteria and perform
the same kind of experiment that Meselson and Stahl did to determine how the
Mars bacteria replicates its DNA. Based on the following equilibrium
centrifugation results, what type of replication would you propose for this new
bacteria?
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