Expansions and contractions of the genetic map relative to the physical map of yeast chromosome III

1988 ◽  
Vol 8 (2) ◽  
pp. 595-604
Author(s):  
L S Symington ◽  
T D Petes

To examine the relationship between genetic and physical chromosome maps, we constructed a diploid strain of the yeast Saccharomyces cerevisiae heterozygous for 12 restriction site mutations within a 23-kilobase (5-centimorgan) interval of chromosome III. Crossovers were not uniformly distributed along the chromosome, one interval containing significantly more and one interval significantly fewer crossovers than expected. One-third of these crossovers occurred within 6 kilobases of the centromere. Approximately half of the exchanges were associated with gene conversion events. The minimum length of gene conversion tracts varied from 4 base pairs to more than 12 kilobases, and these tracts were nonuniformly distributed along the chromosome. We conclude that the chromosomal sequence or structure has a dramatic effect on meiotic recombination.

1988 ◽  
Vol 8 (2) ◽  
pp. 595-604 ◽  
Author(s):  
L S Symington ◽  
T D Petes

To examine the relationship between genetic and physical chromosome maps, we constructed a diploid strain of the yeast Saccharomyces cerevisiae heterozygous for 12 restriction site mutations within a 23-kilobase (5-centimorgan) interval of chromosome III. Crossovers were not uniformly distributed along the chromosome, one interval containing significantly more and one interval significantly fewer crossovers than expected. One-third of these crossovers occurred within 6 kilobases of the centromere. Approximately half of the exchanges were associated with gene conversion events. The minimum length of gene conversion tracts varied from 4 base pairs to more than 12 kilobases, and these tracts were nonuniformly distributed along the chromosome. We conclude that the chromosomal sequence or structure has a dramatic effect on meiotic recombination.


1987 ◽  
Vol 7 (1) ◽  
pp. 68-75 ◽  
Author(s):  
A Gaudet ◽  
M Fitzgerald-Hayes

Centromere DNA from 11 of the 16 chromosomes of the yeast Saccharomyces cerevisiae have been analyzed and reveal three sequence elements common to each centromere, referred to as conserved centromere DNA elements (CDE). The adenine-plus-thymine (A + T)-rich central core element, CDE II, is flanked by two short conserved sequences, CDE I (8 base pairs [bp]) and CDE III (25 bp). Although no consensus sequence exists among the different CDE II regions, they do have three common features of sequence organization. First, the CDE II regions are similar in length, ranging from 78 to 86 bp measured from CDE I to the left boundary of CDE III. Second, the base composition is always greater than 90% A + T. Finally, the A and T residues in these segments are often arranged in runs of A and runs of T residues, sometimes with six or seven bases in a stretch. We constructed insertion, deletion, and replacement mutations in the CDE II region of the centromere from chromosome III, CEN3, designed to investigate the length and sequence requirements for function of the CDE II region of the centromere. We analyzed the effect of these altered centromeres on plasmid and chromosome segregation in S. cerevisiae. Our results show that increasing the length of CDE II from 84 to 154 bp causes a 100-fold increase in chromosome nondisjunction. Deletion mutations removing segments of the A + T-rich CDE II DNA also cause aberrant segregation. In some cases partial function could be restored by replacing the deleted DNA with fragments whose primary sequence or base composition is very different from that of the wild-type CDE II DNA. In addition, we found that identical mutations introduced into different positions in CDE II have very similar effects.


Genetics ◽  
1991 ◽  
Vol 129 (2) ◽  
pp. 343-357 ◽  
Author(s):  
C S Newlon ◽  
L R Lipchitz ◽  
I Collins ◽  
A Deshpande ◽  
R J Devenish ◽  
...  

Abstract DNA was isolated from a circular derivative of chromosome III to prepare a library of recombinant plasmids enriched in chromosome III sequences. An ordered set of recombinant plasmids and bacteriophages carrying the contiguous 210-kilobase region of chromosome III between the HML and MAT loci was identified, and a complete restriction map was prepared with BamHI and EcoRI. Using the high frequency transformation assay and extensive subcloning, 13 ARS elements were mapped in the cloned region. Comparison of the physical maps of chromosome III from three strains revealed that the chromosomes differ in the number and positions of Ty elements and also show restriction site polymorphisms. A comparison of the physical map with the genetic map shows that meiotic recombination rates vary at least tenfold along the length of the chromosome.


Genetics ◽  
1989 ◽  
Vol 123 (1) ◽  
pp. 69-80 ◽  
Author(s):  
R H Borts ◽  
J E Haber

Abstract We have measured gene conversion tract length in strains of the yeast Saccharomyces cerevisiae containing three to six restriction site heterozygosities in a 9-kb interval. Tetrads containing a conversion were identified genetically by nonmendelian segregation of a marker in the middle of the interval. Gene conversions accompanied by a crossover have a tract length of 1.4 kb +/- 0.7 kb, which is indistinguishable from a tract length of 1.6 +/- 0.8 for conversions without an associated exchange. Among tetrads identified first as having a crossover in the interval, the average gene conversion tracts were apparently significantly shorter (0.71 +/- 1). We provide evidence that this apparent difference is due to the method of measuring conversion tracts and does not reflect a real difference in tract length. We also provide evidence that the number and position of restriction site markers alters the apparent distribution of the conversion tracts. More than ninety percent of the conversion tracts spanning three or more sites were continuous.


1986 ◽  
Vol 6 (4) ◽  
pp. 1352-1356
Author(s):  
L L Button ◽  
C R Astell

A yeast Saccharomyces cerevisiae telomeric region was isolated by chromosome walking from HML alpha, the most distal known gene on the chromosome III left (IIIL) end. The terminal heterodisperse 3.3-kilobase (kb) SalI fragment on chromosome IIIL, 8.6 kb distal to HML alpha, was cloned in a circular vector to generate a telomeric probe. Southern hybridization and DNA sequencing analyses indicated that 0.6 kb (+/- 200 base pairs) of 5'-C1-3A-3' simple tandem repeat sequence, adjacent to a 1.2-kb type X ARS region, constitutes the telomere on the chromosome IIIL end, and no type Y' ARS region homologies exist between HML alpha and the IIIL terminus.


1984 ◽  
Vol 99 (5) ◽  
pp. 1559-1568 ◽  
Author(s):  
K S Bloom ◽  
E Amaya ◽  
J Carbon ◽  
L Clarke ◽  
A Hill ◽  
...  

The centromere region of Saccharomyces cerevisiae chromosome III has been replaced by various DNA fragments from the centromere regions of yeast chromosomes III and XI. A 289-base pair centromere (CEN3) sequence can stabilize yeast chromosome III through mitosis and meiosis. The orientation of the centromeric fragments within chromosome III has no effect on the normal mitotic or meiotic behavior of the chromosome. The structural integrity of the centromere region in these genomic substitution strains was examined by mapping nucleolytic cleavage sites within the chromatin DNA. A nuclease-protected centromere core of 220-250 base pairs was evident in all of the genomic substitution strains. The position of the protected region is determined strictly by the centromere DNA sequence. These results indicate that the functional centromere core is contained within 220-250 base pairs of the chromatin DNA that is structurally distinct from the flanking nucleosomal chromatin.


1986 ◽  
Vol 6 (4) ◽  
pp. 1352-1356 ◽  
Author(s):  
L L Button ◽  
C R Astell

A yeast Saccharomyces cerevisiae telomeric region was isolated by chromosome walking from HML alpha, the most distal known gene on the chromosome III left (IIIL) end. The terminal heterodisperse 3.3-kilobase (kb) SalI fragment on chromosome IIIL, 8.6 kb distal to HML alpha, was cloned in a circular vector to generate a telomeric probe. Southern hybridization and DNA sequencing analyses indicated that 0.6 kb (+/- 200 base pairs) of 5'-C1-3A-3' simple tandem repeat sequence, adjacent to a 1.2-kb type X ARS region, constitutes the telomere on the chromosome IIIL end, and no type Y' ARS region homologies exist between HML alpha and the IIIL terminus.


Genetics ◽  
1994 ◽  
Vol 137 (1) ◽  
pp. 5-18 ◽  
Author(s):  
R E Malone ◽  
S Kim ◽  
S A Bullard ◽  
S Lundquist ◽  
L Hutchings-Crow ◽  
...  

Abstract The properties of gene conversion as measured in fungi that generate asci containing all the products of meiosis imply that meiotic recombination initiates at specific sites. The HIS2 gene of Saccharomyces cerevisiae displays a high frequency of gene conversion, indicating that it is a recombination hotspot. The HIS2 gene was cloned and sequenced, and the cloned DNA was used to make several different types of alterations in the yeast chromosome by transformation; these alterations were used to determine the location of the sequences necessary for the high levels of meiotic conversion observed at HIS2. Previous work indicated that the gene conversion polarity gradient is high at the 3' end of the gene, and that the promoter of the gene is not necessary for the high frequency of conversion observed. Data presented here suggest that at least some of the sequences necessary for high levels of conversion at HIS2 are located over 700 bp downstream of the end of the coding region, extend over (at least) several hundred base pairs, and may be quite complex, perhaps involving chromatin structure. Additional data indicate that multiple single base heterologies within a 1-kb interval contribute little to the frequency of gene conversion. This contrasts with other reports about the role of heterologies at the MAT locus.


1987 ◽  
Vol 7 (1) ◽  
pp. 68-75
Author(s):  
A Gaudet ◽  
M Fitzgerald-Hayes

Centromere DNA from 11 of the 16 chromosomes of the yeast Saccharomyces cerevisiae have been analyzed and reveal three sequence elements common to each centromere, referred to as conserved centromere DNA elements (CDE). The adenine-plus-thymine (A + T)-rich central core element, CDE II, is flanked by two short conserved sequences, CDE I (8 base pairs [bp]) and CDE III (25 bp). Although no consensus sequence exists among the different CDE II regions, they do have three common features of sequence organization. First, the CDE II regions are similar in length, ranging from 78 to 86 bp measured from CDE I to the left boundary of CDE III. Second, the base composition is always greater than 90% A + T. Finally, the A and T residues in these segments are often arranged in runs of A and runs of T residues, sometimes with six or seven bases in a stretch. We constructed insertion, deletion, and replacement mutations in the CDE II region of the centromere from chromosome III, CEN3, designed to investigate the length and sequence requirements for function of the CDE II region of the centromere. We analyzed the effect of these altered centromeres on plasmid and chromosome segregation in S. cerevisiae. Our results show that increasing the length of CDE II from 84 to 154 bp causes a 100-fold increase in chromosome nondisjunction. Deletion mutations removing segments of the A + T-rich CDE II DNA also cause aberrant segregation. In some cases partial function could be restored by replacing the deleted DNA with fragments whose primary sequence or base composition is very different from that of the wild-type CDE II DNA. In addition, we found that identical mutations introduced into different positions in CDE II have very similar effects.


Genetics ◽  
1989 ◽  
Vol 123 (1) ◽  
pp. 81-95 ◽  
Author(s):  
E J Louis ◽  
J E Haber

Abstract The presence of the tRNA ochre suppressors SUP11 and SUP5 is found to induce meiosis I nondisjunction in the yeast Saccharomyces cerevisiae. The induction increases with increasing dosage of the suppressor and decreases in the presence of an antisuppressor. The effect is independent of the chromosomal location of SUP11. Each of five different chromosomes monitored exhibited nondisjunction at frequencies of 0.1%-1.1% of random spores, which is a 16-160-fold increase over wild-type levels. Increased nondisjunction is reflected by a marked increase in tetrads with two and zero viable spores. In the case of chromosome III, for which a 50-cM map interval was monitored, the resulting disomes are all in the parental nonrecombinant configuration. Recombination along chromosome III appears normal both in meioses that have no nondisjunction and in meioses for which there was nondisjunction of another chromosome. We propose that a proportion of one or more proteins involved in chromosome pairing, recombination or segregation are aberrant due to translational read-through of the normal ochre stop codon. Hygromycin B, an antibiotic that can suppress nonsense mutations via translational read-through, also induces nonrecombinant meiosis I nondisjunction. Increases in mistranslation, therefore, increase the production of aneuploids during meiosis. There was no observable effect of SUP11 on mitotic chromosome nondisjunction; however some disomes caused SUP11 ade2-ochre strains to appear white or red, instead of pink.


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