Sex Determination by Observation of Barr Body in Teeth Subjected to High Temperatures

The sex of painted turtles (Chrysemys picta) is determined by the incubation temperature of the egg. At high temperatures (> 30 °C), all females are produced, with a transition to all males at most lower temperatures (24–27 °C). However, two of three previous studies have reported that some females also result when incubation temperatures are low (20–22 °C). In this study C. picta eggs were incubated at low temperatures (21.5 and 22.5 °C); however, macroscopic and histological examination of both embryos and hatchlings did not confirm these reports. Thus, C. picta has, at least typically, the pattern of sex determination that is most common among the genera to which it is most closely allied.

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Determination of Sex Chromatin — A New Concept

Acta geneticae medicae et gemellologiae ◽

10.1017/s1120962300011227 ◽

1972 ◽

Vol 21 (1-2) ◽

pp. 149-170

Author(s):

Syed Shane Raza Zaidi

Keyword(s):

Sex Determination ◽

Y Chromosome ◽

X Chromosome ◽

Mother Cell ◽

Daughter Cell ◽

Barr Body ◽

X Chromosomes ◽

Sex Chromatin

SummaryInstead of the random activation and/or inactivation of the X-chromosome in sex determination, as suggested by the Lyon's hypothesis, a proposal is made here that crossingover between the sister- and/or nonsisterstrands at the sticky or nonsticky loci, at heterochromatinizing regions and at the inactivating centers of the centromère, be responsible for the heterochromatinization and/or heteropyknotization of the X-chromosome. (This proposal will be called the Mustafa hypothesis.)Such would be the basis for the activation and/or inactivation of the X-chromatid(s), which would then replicate into a normal or a heterochromatic X-chromosome respectively. The heterochromatic X-chromosome may be transformed into a heteropyknotized mass of sex chromatin (Barr body). Translocation of the Y-chromosome and of some of the autosomes could also result in the same effect. Hence, the number of heterochromatinized X-chromosomes, and/or of heteropyknotized masses (Barr bodies), in each daughter-cell is directly proportional to half the number of chromatids involved in crossingover and/or translocation in the mother-cell.

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Inheritance of Chromosomes, Sex Determination, and the Human Genome

Gender and the Genome ◽

10.1177/2470289718787131 ◽

2018 ◽

Vol 2 (1) ◽

pp. 16-26 ◽

Cited By ~ 1

Author(s):

Nirmalchandra K. Shetty

Keyword(s):

Sex Determination ◽

Y Chromosome ◽

X Chromosome ◽

Cell Biology ◽

Theoretical Research ◽

Barr Body ◽

X Chromosomes ◽

New Model ◽

Hypothesis Model ◽

New Hypothesis

Who is the determining factor for the sex of the offspring—mother, father, or both parents? This fundamental hypothesis proposes a new model of sex determination, challenging the existing dogma that the male Y chromosome of the father is the sole determinant of the sex of the offspring. According to modern science, the 3 X chromosomes (male XY and female XX) are assumed to be similar, and the sex of the offspring is determined after the zygote is formed. In contrast to this, the new hypothesis based on theoretical research proposes that the 3 X chromosomes can be differentiated, based on the presence of Barr bodies. The first X in female XX chromosomes and X in male XY chromosomes are similar as they lack Barr body and are hereby denoted as ‘X’ and referred to as ancestral chromosomes. The second X chromosome in the female cells which is a Barr body, denoted as X, is different. This X chromosome along with the Y chromosome are referred to as parental chromosomes. Sperm with a Y chromosome can only fuse with an ovum containing the ‘X’ chromosome. Similarly, sperm with the ‘X’ chromosome can only fuse with an ovum containing the X chromosome. Cell biology models of gametogenesis and fertilization were simulated with the new hypothesis model and assessed. Only chromosomes that participated in recombination could unite to form the zygote. This resulted in a paradigm shift in our understanding of sex determination, as both parents were found to be equally responsible for determining the sex of the offspring. The gender of the offspring is determined during the prezygotic stage itself and is dependent on natural selection. A new dimension has been given to inheritance of chromosomes. This new model also presents a new nomenclature for pedigree charts. This work of serendipity may contribute to future research in cell biology, gender studies, genome analysis, and genetic disorders including cancer.

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In situ REM imaging of surface processes on ceramic bulk crystals from 300 to 1670 K in a conventional TEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100087616 ◽

1991 ◽

Vol 49 ◽

pp. 660-661

Author(s):

Z. L. Wang ◽

J. Bentley

Keyword(s):

High Temperatures ◽

Image Resolution ◽

Atomic Processes ◽

Crystal Surfaces ◽

Beam Radiation ◽

Surface Areas ◽

Transmission Electron ◽

Reflection Electron Microscopy ◽

Gas Reactions

Studying the behavior of surfaces at high temperatures is of great importance for understanding the properties of ceramics and associated surface-gas reactions. Atomic processes occurring on bulk crystal surfaces at high temperatures can be recorded by reflection electron microscopy (REM) in a conventional transmission electron microscope (TEM) with relatively high resolution, because REM is especially sensitive to atomic-height steps.Improved REM image resolution with a FEG: Cleaved surfaces of a-alumina (012) exhibit atomic flatness with steps of height about 5 Å, determined by reference to a screw (or near screw) dislocation with a presumed Burgers vector of b = (1/3)<012> (see Fig. 1). Steps of heights less than about 0.8 Å can be clearly resolved only with a field emission gun (FEG) (Fig. 2). The small steps are formed by the surface oscillating between the closely packed O and Al stacking layers. The bands of dark contrast (Fig. 2b) are the result of beam radiation damage to surface areas initially terminated with O ions.

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