Lesson 1 of an A Level teaching resource, produced in conjunction with the Charles Darwin Trust, that uses Darwin's work on pigeon breeding and the work of contemporary scientists to explore genetics and evolution.
This first lesson covers the topics of artificial selection and genetics.
The accompanying teacher's notes can be found on our website at www.linnean.org/funkypigeons
Lesson 1 of an A Level teaching resource, produced in conjunction with the Charles Darwin Trust, that uses Darwin's work on pigeon breeding and the work of contemporary scientists to explore genetics and evolution.
This first lesson covers the topics of artificial selection and genetics.
The accompanying teacher's notes can be found on our website at www.linnean.org/funkypigeons
My talk on genome-wide selection components analysis in a fish with male pregnancy (the Gulf pipefish, Syngnathus scovelli) from the Evolution 2017 meeting. Video of presentation available https://www.youtube.com/watch?v=gOdv99wF_TY
Human Clinical Relevance of Developmental and Reproductive Toxicology and Non...Joseph Holson
Presented at Forest Research Institute, May 13, 2004.
Abstract: Experimental animal models are essential to product development and toxicologic screening. The effective use of such models is dependent on the attributes of: validity, sensitivity, reproducibility, and practicability. For the two endpoints of toxicity of most societal concern, developmental effects, and cancer, experience has taught that differences between animals and humans in drug absorption, distribution, metabolism and elimination most often leads to differences in response both qualitatively, and quantitatively. In developmental toxicology, a high degree of concordance between experimental animal results and human outcomes has been demonstrated. Human reproductive outcomes are often concordant with experimental animal data, but this concordance seems to vary more among species as phenotypes diversify with approaching sexual maturity and subsequent reproductive senescence. This increase in phenotypic diversity also presents difficulties in a priori selection of animal models in non-clinical juvenile toxicity testing. Juvenile periods among species can be divided into pre-term neonatal, neonatal, infancy, childhood and adolescence, based on overall central nervous system and reproductive development. However, because physiologic time differs among species, temporality of target-organ maturation should be reconciled with the human pediatric therapeutic scenario prior to animal model selection. The heuristic impact and resultant guidance for proper selection and use of animal models for juvenile toxicity testing will be demonstrated through the use of case studies involving angiotensin-converting enzyme (ACE) inhibitors, quinilones, fluoxetine and isotretinoin.
2 ajob Winter 2001, Volume 1, Number 1 2001 by The MIT P.docxvickeryr87
2 ajob Winter 2001, Volume 1, Number 1
� 2001 by The MIT Press
Pre co ncep tio n Ge nd er S ele ctio n
Preconception Gender Selection1
John A. Robertson, School of Law, University of Texas at Austin
Safe and effective methods of preconception gender selection through �ow cytometric separation
of X- and Y-bearing sperm could greatly increase the use of gender selection by couples contem-
plating reproduction. Such a development raises ethical, legal, and social issues about the impact
of such practices on offspring, on sex ratio imbalances, and on sexism and the status of women.
This paper analyzes the competing interests in preconception gender selection, and concludes that
its use to increase gender variety in a family, and possibly for selecting the gender of �rstborn,
might in many instances be ethically acceptable.
Advances in genetics and reproductive technology
present prospective parents with an increasing
number of choices about the genetic makeup of
their children. Those choices now involve the use
of carrier and prenatal screening techniques to
avoid the birth of children with serious genetic dis-
ease, but techniques to choose nonmedical charac-
teristics will eventually be available. One
nonmedical characteristic that may soon be within
reach is the selection of offspring gender by pre-
conception gender selection (PGS).
Gender selection through prenatal diagnosis
and abortion has existed since the 1970s. More re-
cently, preimplantation sexing of embryos for
transfer has been developed (Tarin and Handyside
1993; The Ethics Committee of the American So-
ciety of Reproductive Medicine 1999). Yet prena-
tal or preimplantation methods of gender selection
are unattractive because they require abortion or a
costly, intrusive cycle of in vitro fertilization (IVF)
and embryo discard. Attempts to separate X- and
Y-bearing sperm for preconception gender selec-
tion by sperm swim-up or swim-through tech-
niques have not shown consistent X- and Y-sperm
cell separation or success in producing offspring of
the desired gender.
The use of �ow cytometry to separate X- and Y-
bearing sperm may turn out to be a much more re-
liable method of enriching sperm populations for
insemination. Laser beams passed across a �owing
array of specially dyed sperm can separate most of
the 2.8% heavier X- from Y-bearing sperm, thus
producing an X-enriched sperm sample for insemi-
nation.2 Flow cytometry has been used successfully
in over 400 sex selections in rabbit, swine, ovine,
and bovine species, including successive genera-
tions in swine and rabbit (Fugger et al. 1998). A
human pregnancy was reported in 1995 (Levinson,
Keyvanfar, and Wu 1995).
The United States Department of Agriculture
(USDA), which holds a patent on the �ow cy-
tometry separation process, has licensed the Genet-
ics and IVF Institute in Fairfax, Virginia, to study
the safety and ef�cacy of the technique for medical
and “family balancing” reasons in an institutional
review boa.
When males only contribution to offspring is their sperm, females .pdfanurag1231
When males\' only contribution to offspring is their sperm, females are particularly choosy. With
this high level of female choice, sexual ornaments are seen in males, where the ornaments reflect
the male\'s social status. Two hypotheses have been proposed to conceptualize the genetic
benefits from female mate choice.
First, the good genes hypothesis suggests that female choice is for higher genetic quality and that
this preference is favored because it increases fitness of the offspring. This includes Zahavi\'s
handicap hypothesis and Hamilton and Zuk\'s host and parasite arms race. Zahavi\'s handicap
hypothesis was proposed within the context of looking at elaborate male sexual displays. He
suggested that females favor ornamented traits because they are handicaps and are indicators of
the male\'s genetic quality. Since these ornamented traits are hazards, the male\'s survival must
be indicative of his high genetic quality in other areas. In this way, the degree that a male
expresses his sexual display indicates to the female his genetic quality. Zuk and Hamilton
proposed a hypothesis after observing disease as a powerful selective pressure on a rabbit
population. They suggested that sexual displays were indicators of resistance of disease on a
genetic level.
Such \'choosiness\' from the female individuals can be seen in wasp species too, especially
among Polistes dominula wasps. The females tend to prefer males with smaller, more elliptically
shaped spots than those with larger and more irregularly shaped spots. Those males would have
reproductive superiority over males with irregular spots.
Fisher\'s hypothesis of runaway sexual selection suggests that female preference is genetically
correlated with male traits and that the preference co-evolves with the evolution of that trait, thus
the preference is under indirect selection. Fisher suggests that female preference began because
the trait indicated the male’s quality. The female preference spread, so that the females’ offspring
now benefited from the higher quality from specific trait but also greater attractiveness to mates.
Eventually, the trait will only represent attractiveness to mates and no longer represent increased
survival.
An example of mate choice by genes is seen in the cichlid fish Tropheus moorii where males
provide no parental care. An experiment found that a female T. moorii is more likely to choose a
mate with the same color morph as her own. In another experiment, females have been shown to
share preferences for the same males when given two to choose from, meaning some males get
to reproduce more often than others
Solution
When males\' only contribution to offspring is their sperm, females are particularly choosy. With
this high level of female choice, sexual ornaments are seen in males, where the ornaments reflect
the male\'s social status. Two hypotheses have been proposed to conceptualize the genetic
benefits from female mate choice.
First, the good genes hypothesis.
This presentation is the third in a four part webinar series on internal parasites in sheep and goats. This presentation focuses on the diagnostic tools available to producers to help them control parasites in the flocks and herds. The presentation is by Susan Schoenian, University of Maryland Extension Sheep & Goat Specialist.
Killing one day-old male chicks, do we have alternatives (summery)-1Harm Kiezebrink
Throughout the world, male chicks from layer breeds are killed just after hatching, as they are not profitable as regards the production of meat. The Dutch and European parliaments have insisted on research into possible alternatives to the killing of day-old chicks. In the present study we have investigated Dutch public opinion on the acceptability of these alternatives by means of discussions in so- called focus groups and via a public survey through computer-aided personal interviews (CAPI).
To inform the participants about the subject, a film was made to explain the current practice and introduce a number of technological alternatives that would prevent development of male embryos, as well as the possibility of creating a ‘dual-purpose chicken’ that would allow male chicks to be used for meat production.
The topics addressed in the study included the willingness of participants to pay a premium for eggs and chicken meat, were it necessary to prevent killing of male chicks. Focus-group discussions showed that many participants were unaware of the current practice of killing male chicks, and were shocked by this practice.
However, once informed, the participants seemed able to take various considerations into account and rank the alternatives. The alternatives ‘looking into the fresh egg (to determine sex of the egg and not incubate male eggs)’, and ‘dual-purpose chickens’ scored best out of all the possible alternatives, and higher than maintaining the current practice. ‘Influencing the laying hens such that they produce fewer male eggs’ scored the same as maintaining the current practice.
The use of ‘genetic modification to facilitate looking into the fresh egg’ scored only slightly lower than maintaining the current practice. Alternatives whereby developing male embryos die, or are killed, scored lower than maintaining the current practice.
Similar to The effects of bot fly parasitism on mate choice in white-footed mice (Peromyscus leucopus) (20)
Killing one day-old male chicks, do we have alternatives (summery)-1
The effects of bot fly parasitism on mate choice in white-footed mice (Peromyscus leucopus)
1. The Effects of Bot Fly Parasitism on Mate Choice in White-Footed Mice ( Peromyscus leucopus ) Michael J. Cramer and Guy N. Cameron Department of Biological Sciences University of Cincinnati
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6. Peromyscus Bot Fly Life Cycle Females lay eggs in host habitat. Hosts pick up newly hatched larvae . Larvae migrate to inguinal region and develop warble. After 3 rd instar, larvae exit host and burrow underground to pupate. Flies emerge and mate at aggregation sites. 5 days 21 days P. Meyer C. N. Shiffer M. J. Cramer
13. Body Size and Mate Choice Paired t-test t 15 = 2.765; p = 0.014
14. Body Size and Mate Choice F 1, 14 = 14.732, p = 0.001
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Editor's Notes
Sexual selection is an important force in evolutionary and behavioral ecology since Darwin proposed it as an alternative hypothesis to explain the existance of traits inconsistent with natural selection SS is similar to NS except individuals are selected to maximize number of mating opportunities through two mechanisms w/in sexes--individuals compete for access to mates b/t sexes--mating is determined by one sex choosing mates based on some characteristic strength of sexual selection based on mating system in which mating opportunities are limited
Parasites could disrupt sexual selection by affecting competitive ability and/or affecting mate choice
Infected males may be avoided as mates for the following reasons 1. females may develop infections 2. parasites may be passed to offspring neither of these is probable based on bot fly biology 3. male has low resistance to parasites which could be passed to offspring (low genetic quality)
grids were .25 ha reproductive condition based on location of testes for males and whether vagina was open or closed for females
trials videotaped to reduce mouse response to observer chamber divisions: large central section flanked by 2 smaller sections male separated from female: allowed female to smell male but did not allow males to interact
contrary to expectations females spent significantly more time with infected males
males gain weight with infection independent of weight of parasite
Zahavi: males may be better providers for their offspring and/or may confer a genetic advantage (tolerance for common parasite)