Increasing the transmission rate of the extra chromosome in a trisomic Nicotiana sylvestris line by modifying the means of pollination

1988 ◽  
Vol 76 (6) ◽  
pp. 891-896 ◽  
Author(s):  
M. Niizeki ◽  
K. Saito
Keyword(s):  
Transmission Rate ◽  
Extra Chromosome ◽  
Nicotiana Sylvestris

TRISOMICS OF AVENA STRIGOSA

1975 ◽  
Vol 17 (2) ◽  
pp. 151-166 ◽  
Author(s):  
Tibor Rajhathy
Keyword(s):  
Transmission Rate ◽  
Extra Chromosome ◽  
Chromosome Length ◽  
Chromosome Morphology ◽  
Balance Theory ◽  
Primary Trisomics ◽  
Qualitative And Quantitative ◽  
Dosage Effects ◽  
Avena Strigosa ◽  
Small Seed

A set of seven primary trisomics and seven derived types were produced in Avena strigosa Schreb., a diploid oat species. Each trisomic type had a distinct phenotype. The primary trisomics were identified on the basis of plant and chromosome morphology. Although fertility (seed-set) and the frequency of transmission of the extra chromosome varied among selfed progenies of the various trisomics, each trisomic can be maintained. The trisomics occurred at a higher frequency in small seed fractions than in samples of large seeds. No straightforward relationship was apparent between chromosome length and trivalent formation but some association between trivalent formation and transmission rate was observed.Several qualitative and quantitative traits were compared between the primary telotri-somics, between these and the disomic and between opposite arm telotrisomics and their corresponding primary trisomic. It was concluded that the results are more compatible with dosage effects than with the gene balance theory.

Certation between euploid and aneuploid pollen grains from a tertiary trisomic of rye, Secale cereale L.

Genome ◽  
1987 ◽  
Vol 29 (2) ◽  
pp. 353-356 ◽  
Author(s):  
J. Janse
Keyword(s):  
Secale Cereale ◽  
Seed Weight ◽  
Genetic Factors ◽  
Seed Set ◽  
Transmission Rate ◽  
Extra Chromosome ◽  
Pollen Grains ◽  
Decisive Role ◽  
Germination Percentage ◽  
Secale Cereale L

Male transmission of the translocated extra chromosome 5R3R was studied in a tertiary trisomic of rye (Secale cereale L.) using two pollination densities. With abundant pollen, male transmission reached 4%. When a mean of four pollen grains were brought on every stigma (restricted pollination), a transmission rate of 20% was obtained. Seed set, mean seed weight, germination percentage, and the percentage of plants finally surviving were lower in the case of restricted pollination. It was concluded that certation between euploid and aneuploid pollen grains plays a decisive role in male transmission of the translocated chromosome. Although it was previously shown that aneuploid microspores have a delayed development, a large proportion must have reached maturity before anthesis. Therefore, genetic factors determining male transmission rate will primarily be expressed during pollen germination and tube growth rather than before anthesis. Key words: rye, tertiary trisomic, euploid pollen grains, aneuploid pollen grains, certation.

Cytogenetics of an unstable trisomie in barley (Hordeum vulgare)

Genome ◽  
1993 ◽  
Vol 36 (2) ◽  
pp. 350-355
Author(s):  
R. J. Singh ◽  
T. Tsuchiya
Keyword(s):  
Transmission Rate ◽  
Meiotic Chromosome ◽  
Extra Chromosome ◽  
Low Frequency ◽  
Chromosome Elimination ◽  
Metacentric Chromosome ◽  
Chromosome 3 ◽  
Chromosome Behavior ◽  
Chromosome Configuration ◽  
Average Transmission

The origin, identification, meiotic chromosome behavior, and breeding behavior of an unstable trisomic barley were studied. The extra chromosome originated by breakage and fusion of an acrocentric chromosome 3 in a plant from an F2 population of a cross between acrotrisomic 3L3S (2n = 14 + 1 acro3L3S) and a balanced lethal stock, xc. (xantha) ac (albino). The F2 population segregated only for the albino trait. The genotypic constitution of the trisomic plant was ac ac (for both normal chromosome 3) and Ac (for the unstable metacentric chromosome). The unstable extra metacentric chromosome was designated as metacentric 3B (abbreviated as meta3B). Meiotic chromosome behavior in plants with 2n = 14 + 1 meta3B differed from plant to plant and within spikes. Some plants showed only trisomic cells with a chromosome configuration of 1 III + 6 II and 7 II + 1 I at metaphase I, whereas other plants showed both trisomie and disomic cells (7 II) that resulted from the elimination of the extra meta3B. The frequency of ring trivalents was low (6.8%). An average transmission rate of unstable meta3B ranged from 4.3 to 12.9%. The elimination of meta3B, and hence loss of the dominant Ac allele, resulted in albino seedlings as well as white stripes on plants, leaves, and spikes. Chromosome numbers of albino seedlings in the progeny of 2n = 14 + 1 meta3B were all diploid (2n = 14), while green seedlings contained 2n = 14 + 1 meta3B. However, progenies of some spikes of one trisomic plant showed a low frequency of green diploids and metatrisomics (2n = 14 + 1 meta3B), which was attributed to crossing-over.Key words: aneuploid, chromosome elimination, kinetochore, meta3B.

TRISOMIC TRANSMISSION IN LOTUS PEDUNCULATUS

1968 ◽  
Vol 10 (3) ◽  
pp. 648-654 ◽  
Author(s):  
Chi-Chang Chen ◽  
W. F. Grant
Keyword(s):  
Pollen Germination ◽  
Transmission Rate ◽  
Extra Chromosome ◽  
Low Frequency ◽  
Pollen Grains ◽  
Tube Growth ◽  
Male Gametes ◽  
Meiotic Irregularities ◽  
Significant Difference ◽  
Lotus Pedunculatus

Transmission of the extra chromosome was studied for four primary trisomic types of Lotus pedunculatus Cav., named Broad, Pointed, Narrow, and Small (trisomic for chromosomes 3, 4, 5 and 6, respectively). Despite the low frequency of transmission (average 9.2%), parental trisomics were recovered in all of the four trisomic types. No significant difference was found between pollen and ovule transmission. It was suggested that either there is no difference in germination and tube growth between the n and n + 1 pollen grains, or selection against the n + 1 male gametes in pollen germination and tube growth is balanced by the mechanism (s) selecting against the n + 1 female gametes. Although there were variations in transmission rate within the same trisomic types, the shorter extra chromosomes tended to be transmitted more frequently than the longer ones. This was interpreted as reflecting the degree of genic unbalance created by the extra chromosome in gametes and zygotes. The longer the extra chromosome, the greater would be the unbalance, and hence the less chance there would be for the n + 1 gametes and 2n + 1 zygotes to be viable. The trisomic types Small and Narrow produced a few unrelated trisomics in their progenies. It was considered that meiotic irregularities in these trisomic types could account for the production of such unrelated trisomics.

Interfacing of a TEM/STEM System to a Computer

1981 ◽  
Vol 39 ◽  
pp. 250-251
Author(s):  
P. Hagemann
Keyword(s):  
Image Analysis ◽  
Transmission Rate ◽  
Analytical Electron Microscopy ◽  
Signal Beam ◽  
Automated Image Analysis ◽  
Beam Deflection ◽  
External Control ◽  
Computer Input ◽  
Instrument Control ◽  
Data Acquisition And Processing

The use of computers in the analytical electron microscopy today shows three different trends (1) automated image analysis with dedicated computer systems, (2) instrument control by microprocessors and (3) data acquisition and processing e.g. X-ray or EEL Spectroscopy.While image analysis in the T.E.M. usually needs a television chain to get a sequential transmission suitable as computer input, the STEM system already has this necessary facility. For the EM400T-STEM system therefore an interface was developed, that allows external control of the beam deflection in TEM as well as the control of the STEM probe and video signal/beam brightness on the STEM screen.The interface sends and receives analogue signals so that the transmission rate is determined by the convertors in the actual computer periphery.

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