Meiotic behavior of chromosomal polymorphisms in populations of the deer mouse (Peromyscus beatae) /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1989.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | The meiotic behavior of autosomal and sex chromosomal polymorphisms of Peromyscus beatae was examined from whole cell complements of synaptonemal complex (SC), diakinesis/metaphase I, and metaphase II preparations. Included in the analyses were polymorphisms involving pericentric inversions of chromosomes 1, 2, 22, and 23; heteromorphism for an interstitial C-band positive heterochromatic addition to chromosome 22; a terminal euchromatic addition to chromosome 22; and polymorphism in the amount of C-band positive heterochromatin on the short arms of both the X and Y chromosomes. Pericentric inversion heterozygosity was not generally found to disrupt meiosis. Instead of inversion loop formation, the heterozygous chromosomes paired by heterosynaptic straight pairing, resulting in fully paired, normal appearing bivalents. Crossing over as shown by chiasmata position was limited to the homologous portions of the bivalents. However, two individuals heterozygous for pericentric inversions of chromosome 1 were observed to exhibit late pairing of the inverted regions. Additionally, these late pairing ends frequently associated with the sex chromosomes, possibly resulting in a reduction of fertility.Two individuals were heterozygous for an interstitial heterochromatic addition to chromosome 22. Pairing of this bivalent occurred in either of two different manners, both of which resulted in unequal axial lengths. Each of the pairing conformations was converted into fully paired bivalents through the process of synaptic adjustment. Synaptic adjustment also was responsible for the transition of unequal axial lengths in bivalents to fully paired bivalents with no apparent abnormalities in the individual with a euchromatic addition to chromosome 22. Variation in the amount of heterochromatin in the short arms of the X and Y chromosomes of P. beatae was found to manifest itself during early to mid pachynema as axial length differences within the pairing region of the sex bivalent. It is hypothesized that this variation is produced and propagated by unequal crossing over within the heterochromatic short arms, leading to unequal chiasmata in diakinesis/metaphase I bivalents and unequal chromatid lengths in metaphase II chromosomes. Crossing over within the heterochromatin of the X and Y chromosomes supports the hypothesis that there is a fundamental difference between sex chromosome heterochromatin and autosomal heterochromatin. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Zoology." |
| Physical Description: | xii, 116 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |