A cross was performed between a yeast strain that requires methionine and lysine for growth (met− lys−)and another yeast strain, which is met+ lys+. One hundred asci were dissected, and colonies were grownfrom the four spores in each ascus. Cells from thesecolonies were tested for their ability to grow on petriplates containing either minimal medium (min), min+ lysine (lys), min + methionine (met), or min + lys+ met. The asci could be divided into two groupsbased on this analysis:Group 1: In 89 asci, cells from two of the four spore colonies couldgrow on all four kinds of media, while the other two spore coloniescould grow only on min + lys + met.Group 2: In 11 asci, cells from one of the four spore colonies couldgrow on all four kinds of petri plates. Cells from a second one ofthe four spore colonies could grow only on min + lys plates andon min + lys + met plates. Cells from a third of the four sporecolonies could only grow on min + met plates and on min + lys+ met. Cells from the remaining colony could only grow on min+ lys + met.a. What are the genotypes of each of the sporeswithin the two groups of asci?b. Are the lys and met genes linked? If so, what is themap distance between them?c. If you could extend this analysis to many moreasci, you would eventually find some asci with adifferent pattern. For these asci, describe the phenotypes of the four spores. List these phenotypesas the ability of dissected spores to form colonieson the four kinds of petri plates.
A cross was performed between a yeast strain that requires methionine and lysine for growth (met− lys−)
and another yeast strain, which is met+ lys+. One hundred asci were dissected, and colonies were grown
from the four spores in each ascus. Cells from these
colonies were tested for their ability to grow on petri
plates containing either minimal medium (min), min
+ lysine (lys), min + methionine (met), or min + lys
+ met. The asci could be divided into two groups
based on this analysis:
Group 1: In 89 asci, cells from two of the four spore colonies could
grow on all four kinds of media, while the other two spore colonies
could grow only on min + lys + met.
Group 2: In 11 asci, cells from one of the four spore colonies could
grow on all four kinds of petri plates. Cells from a second one of
the four spore colonies could grow only on min + lys plates and
on min + lys + met plates. Cells from a third of the four spore
colonies could only grow on min + met plates and on min + lys
+ met. Cells from the remaining colony could only grow on min
+ lys + met.
a. What are the genotypes of each of the spores
within the two groups of asci?
b. Are the lys and met genes linked? If so, what is the
map distance between them?
c. If you could extend this analysis to many more
asci, you would eventually find some asci with a
different pattern. For these asci, describe the
as the ability of dissected spores to form colonies
on the four kinds of petri plates.
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