exm2_ans

exm2_ans - MIT Department of Biology 7.28, Spring 2005 -...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
______________________________ MIT Department of Biology 7.28, Spring 2005 - Molecular Biology 7.28 Spring 2005 Exam Two Name ______________________________ Question 1 _____/ 30 points Question 2 _____/ 20 points Question 3 _____/26 points Question 4 _____/24 points Total _____/100 points 1
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
7.28 Spring 2005 Exam Two Name ______________________________ Question 1 (30 Points total). You have discovered a new species of yeast ( M. catecus ) that is able to switch mating types in a manner similar to the normal budding yeast, S. cerevisiae . M. catecus cells exist in three forms: haploids with the b mating type, haploids with the b mating type, and b/ b diploids. The genome sequence of M. catecus is not yet known. You succeed in cloning the MAT locus from one specific isolate of M. catecus, called strain H. Unfortunately, strain H grows poorly in the lab, and its mating type is unknown. Using this cloned DNA, you make a radioactive probe and use this DNA to probe a genomic Southern blot of total M. catecus DNA that has been digested with the restriction enzyme EcoRI. The DNA from three different cultures of a strain well-adapted to lab growth conditions is present on the blot. The cultures contained the following types of cells: (1) b cells, (2) b cells and (3) b/ b diploid cells. Cell type: 7 4 3 2 kb 0.5 b b/ b b Size 1 2 3 Markers Film: strain H MAT probe 1a (6 points) Based on these data, what size EcoRI fragment carries the MAT locus? Also, which mating type was strain H? Briefly explain your answers. The 2.5 kB fragment carries the MAT locus. Strains of mating types b and b should be different at their MAT locus since this contains the genes that determine mating type. The 2.5 kB fragment is present in b strain but not in b strain indicating that this fragment most likely contains the MAT locus. Strain H is b type. The probe made from its MAT locus recognizes two bands in the b strain-one copy at the MAT locus and one copy in the HML/HMR-like silent locus. The probe only recognizes one band in the b strain-the one copy in its HML/HMR-like silent locus. 2
Background image of page 2
7.28 Spring 2005 Exam Two Name ______________________________ As is true in budding yeast, M. catecus encodes a protein that introduces a double-stranded break (DSB) at the MAT locus. Using your cloned MAT DNA as a substrate, you are able to observe this DNA cleavage in M. catecus cell extracts. A schematic map of the MAT clone is shown below, as are the results of some in vitro DNA cleavage assays analyzed by native agarose gel. No Extract + Extract Size Markers 1 2 3 4 - HindIII 6 3 2 1 kb native agarose gel - HindIII 0.5 pMcMAT1 MAT Kan r ori HindIII HindIII Enzyme: 5000 bp 1b (5 points) Based on these data, draw on the schematic of the MAT clone where the M. catecus nuclease cleaves the DNA.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/11/2011 for the course BIO 7.344 taught by Professor Bobsauer during the Spring '08 term at MIT.

Page1 / 13

exm2_ans - MIT Department of Biology 7.28, Spring 2005 -...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online