Please help me out with this problem...I have no clue how to even approach this problem and I need to figure out URGENTLY! Thank you all in advance for your input!! ^^======
You carry out a large scale cross between the indicated two strains of Neurospora crassa, and observed a number of aberrant asci, five of which are shown below:
A m B x a + b
1)
A m B
A m B
A m B
A + b
a m B
a + B
a + b
a + b
2)
A m B
A m B
A m b
A m b
a m B
a + B
a + b
a + b
3)
A m B
A m B
A m b
A + b
a + B
a + B
a + b
a + b
4)
A m B
A m B
A m b
a m B
a m B
a + b
a + b
5)
A m B
A m B
A + b
A + b
a + B
a + B
a + b
a + b
The colleges hwo provided the strains insists that they are both deficient in the same geen in the DNA mismatch repair pathyway. The results of your cross seem to contradict this assertion.
a) which of the asci would you exhibit as evidence that your colleage is incorrect?
b) Which ascus or asci provide the best evidence that DNA mismatch repair in these strains is not 100% efficient?
c) Among all asci resulting from meioses in which heteroduplexes form across the m/+ region, what proortion of asci will be tetratype for the A and B markers and also show 4:4 segregation of m : + , under the assumption that 43% of heteroduplexes in the region are not corrected, 32% are corrected to m and 25% are corrected to +? State and justify any assumptions you had to make in order to answer this question. Explain origin of all spores in ascus (3).
