Genetic Dominance & Cellular Processes

In learning genetics, many students misunderstand and misinterpret what “dominance” means. Understanding is easier if students realize that dominance is not a mechanism, but rather a consequence of underlying cellular processes. For example, metabolic pathways are often little affected by changes in enzyme concentration. This means that enzyme-producing alleles usually show complete dominance. For genes producing nonenzymatic proteins such as collagen or hemoglobin, the amount of product matters, and dominance relationships are more complicated. Furthermore, with hemoglobin, dominance can change depending on what aspect of the phenotype is being studied and on the environmental conditions. X-linked genes are a special case, whether enzymatic or not. Because of X-chromosome inactivation, only one X-linked allele can be active in a cell, which means that the concept of dominance cannot be applied at the cellular level. Instead, a type of dominance is demonstrated at the individual level; but even so, dominant traits may fail to be expressed, and recessive traits can be expressed. Teaching not only what is happening but why it\u27s happening will give students a deeper understanding, not only of dominance relationships, but of the underlying cellular processes as well

Human Evolution

A common characteristic of humans is a desire to know their roots. This is evident not only in the tracing of family ancestries, but in the excitement about and attention given to the study of the roots of our entire species - the study of human evolution. We have, over the past few million years, evolved from an ape-like ancestor to modern Homo sapiens. Like evolution in general, the fact of human evolution is as firmly established as anything in science. There are, however, differences among scientists concerning details of this process. In this paper I will give an historical overview and summary of our knowledge of human evolution, and will focus on current disagreements

Ecology of Iowa Drosophila II. Lowland Forest and Sand Prairie

The seasonal abundances of Drosophila species collected from a lowland forest community and from a sand prairie community in northeastern Iowa are compared. With some important exceptions, the patterns seen in the lowland forest community were similar to what had been observed in a previous collection (Jennings et al. 1985). Fewer species and many fewer individuals were collected from the sand prairie community, although in general the patterns seen were similar to those of the lowland forest community. Strong evidence of microhabitat differentiation was seen in both communities. In contrast to our previous study, none of the seasonal abundance patterns were significantly correlated with temperature

\u27Eve\u27 in Africa: Human Evolution Meets Molecular Biology

Recent advances in the study of human origins have increased our understanding of our ancestors. There have been new, major fossil finds. WT 17000, a 2.5 million-year-old robust Australopithecus found in Kenya (Walker et al. 1986), led to a revision of early hominid phylogeny (Delson 1986; 1987). Existing fossil materials have been reassessed. For example, Tattersall (1986) maintains that at least two unrecog­- nized hominid species (Homo neanderthalensis, H. hei­ delbergensis and possibly H. steinheimensis ) existed be­ tween the times of H . erectus and fully modern H . sapiens

Ecology of Iowa Drosophila I. Lowland Forest

We have studied the seasonal abundances of Drosophila species collected from a lowland forest community in northeastern Iowa. Eleven species were collected of which six were collected in appreciable numbers (over 20 individuals). One species, D. affinis, is dominant until early summer when it virtually disappears and a second species, D. tripunctata, becomes dominant. Two other species, D. falleni and D. robusta, also are very common early in the year and collected much less frequently later. It is hypothesized that temperature is a critical factor in determining these seasonal patterns

Local Ecology and Multiple Mating in a Natural Population of Drosophila melanogaster

The measurement of fitness components in natural populations is among the most important problems of population genetics. Much effort has been devoted to the measurement of one aspect of the reproductive component of fitness, the storage and use of sperm by females

The 21 cm Signature of Cosmic String Wakes

We discuss the signature of a cosmic string wake in 21cm redshift surveys. Since 21cm surveys probe higher redshifts than optical large-scale structure surveys, the signatures of cosmic strings are more manifest in 21cm maps than they are in optical galaxy surveys. We find that, provided the tension of the cosmic string exceeds a critical value (which depends on both the redshift when the string wake is created and the redshift of observation), a cosmic string wake will generate an emission signal with a brightness temperature which approaches a limiting value which at a redshift of $z + 1 = 30$ is close to 400 mK in the limit of large string tension. The signal will have a specific signature in position space: the excess 21cm radiation will be confined to a wedge-shaped region whose tip corresponds to the position of the string, whose planar dimensions are set by the planar dimensions of the string wake, and whose thickness (in redshift direction) depends on the string tension. For wakes created at $z_i + 1 = 10^3$, then at a redshift of $z + 1 = 30$ the critical value of the string tension $\mu$ is $G \mu = 6 \times 10^{-7}$, and it decreases linearly with redshift (for wakes created at the time of equal matter and radiation, the critical value is a factor of two lower at the same redshift). For smaller tensions, cosmic strings lead to an observable absorption signal with the same wedge geometry.Comment: 11 pages, 4 figures; a couple of comments added in the discussion sectio

GLIMPSE: I. A SIRTF Legacy Project to Map the Inner Galaxy

GLIMPSE (Galactic Legacy Infrared Mid-Plane Survey Extraordinaire), a SIRTF Legacy Science Program, will be a fully sampled, confusion-limited infrared survey of the inner two-thirds of the Galactic disk with a pixel resolution of \~1.2" using the Infrared Array Camera (IRAC) at 3.6, 4.5, 5.8, and 8.0 microns. The survey will cover Galactic latitudes |b| <1 degree and longitudes |l|=10 to 65 degrees (both sides of the Galactic center). The survey area contains the outer ends of the Galactic bar, the Galactic molecular ring, and the inner spiral arms. The GLIMPSE team will process these data to produce a point source catalog, a point source data archive, and a set of mosaicked images. We summarize our observing strategy, give details of our data products, and summarize some of the principal science questions that will be addressed using GLIMPSE data. Up-to-date documentation, survey progress, and information on complementary datasets are available on the GLIMPSE web site: www.astro.wisc.edu/glimpse.Comment: Description of GLIMPSE, a SIRTF Legacy project (Aug 2003 PASP, in press). Paper with full res.color figures at http://www.astro.wisc.edu/glimpse/glimpsepubs.htm

Five Kepler target stars that show multiple transiting exoplanet candidates

We present and discuss five candidate exoplanetary systems identified with the Kepler spacecraft. These five systems show transits from multiple exoplanet candidates. Should these objects prove to be planetary in nature, then these five systems open new opportunities for the field of exoplanets and provide new insights into the formation and dynamical evolution of planetary systems. We discuss the methods used to identify multiple transiting objects from the Kepler photometry as well as the false-positive rejection methods that have been applied to these data. One system shows transits from three distinct objects while the remaining four systems show transits from two objects. Three systems have planet candidates that are near mean motion commensurabilities---two near 2:1 and one just outside 5:2. We discuss the implications that multitransiting systems have on the distribution of orbital inclinations in planetary systems, and hence their dynamical histories; as well as their likely masses and chemical compositions. A Monte Carlo study indicates that, with additional data, most of these systems should exhibit detectable transit timing variations (TTV) due to gravitational interactions---though none are apparent in these data. We also discuss new challenges that arise in TTV analyses due to the presence of more than two planets in a system.Comment: Accepted to Ap

Advancing Alternative Analysis: Integration of Decision Science.

Decision analysis-a systematic approach to solving complex problems-offers tools and frameworks to support decision making that are increasingly being applied to environmental challenges. Alternatives analysis is a method used in regulation and product design to identify, compare, and evaluate the safety and viability of potential substitutes for hazardous chemicals.Assess whether decision science may assist the alternatives analysis decision maker in comparing alternatives across a range of metrics.A workshop was convened that included representatives from government, academia, business, and civil society and included experts in toxicology, decision science, alternatives assessment, engineering, and law and policy. Participants were divided into two groups and prompted with targeted questions. Throughout the workshop, the groups periodically came together in plenary sessions to reflect on other groups' findings.We conclude the further incorporation of decision science into alternatives analysis would advance the ability of companies and regulators to select alternatives to harmful ingredients, and would also advance the science of decision analysis.We advance four recommendations: (1) engaging the systematic development and evaluation of decision approaches and tools; (2) using case studies to advance the integration of decision analysis into alternatives analysis; (3) supporting transdisciplinary research; and (4) supporting education and outreach efforts