Barbara McClintock - Wikipedia
Got a News Tip? The relationship produced some clear hits (“NYPD Blue,” “ Doogie Bochco replaced him with former “L.A. Law” co-star Jimmy Smits, His second wife, Barbara Bosson, co-starred in “Hill Street Blues,”. Editorial Reviews. About the Author. Grace Lebow and Barbara Kane, the co- founders of Aging How To Deal With Difficult Aging Parents: A Relationship Guide For Stressed Out Adult Children. How To Deal With .. Angel Smits · out of 5. Barbara McClintock (June 16, – September 2, ) was an American scientist and She was close to her father, but had a difficult relationship with her mother, tension that began . During this same period, McClintock hypothesized that the tips of Martha Minerva Franklin · Carolyn M. Mazure · Helen L. Smits.
He invited her to Stanford to undertake the study. She successfully described the number of chromosomes, or karyotypeof N.
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Beadle said "Barbara, in two months at Stanford, did more to clean up the cytology of Neurospora than all other cytological geneticists had done in all previous time on all forms of mold. The seed in 10 is colorless, there is no Ac element present and Ds inhibits the synthesis of colored pigments called anthocyanins. In 11 to 13, one copy of Ac is present. Ds can move and some anthocyanin is produced, creating a mosaic pattern.
In the kernel in panel 14 there are two Ac elements and in 15 there are three. In the summer of at Cold Spring Harbor LaboratoryMcClintock began systematic studies on the mechanisms of the mosaic color patterns of maize seed and the unstable inheritance of this mosaicism.
She found that the Dissociation did not just dissociate or cause the chromosome to break, it also had a variety of effects on neighboring genes when the Activator was also present, which included making certain stable mutations unstable. In earlyshe made the surprising discovery that both Dissociation and Activator could transpose, or change position, on the chromosome.
The size of the colored spot on the seed is determined by stage of the seed development during dissociation. McClintock also found that the transposition of Ds is determined by the number of Ac copies in the cell. She referred to Dissociation and Activator as "controlling units"—later, as "controlling elements"—to distinguish them from genes. She hypothesized that gene regulation could explain how complex multicellular organisms made of cells with identical genomes have cells of different function.
In summershe reported her work on the origin and behavior of mutable loci in maize at the annual symposium at Cold Spring Harbor Laboratory, presenting a paper of the same name.
The paper delved into the instability caused by Ds and Ac or just Ac in four genes, along with the tendency of those genes to unpredictably revert to the wild phenotype. She also identified "families" of transposons, which did not interact with one another. She published a paper in Genetics inwhere she presented all her statistical data, and undertook lecture tours to universities throughout the s to speak about her work.
She was interested in studying the evolution of maize through chromosomal changes,  and being in South America would allow her to work on a larger scale. McClintock explored the chromosomal, morphological, and evolutionary characteristics of various races of maize. Over the years I have found that it is difficult if not impossible to bring to consciousness of another person the nature of his tacit assumptions when, by some special experiences, I have been made aware of them.
This became painfully evident to me in my attempts during the s to convince geneticists that the action of genes had to be and was controlled. It is now equally painful to recognize the fixity of assumptions that many persons hold on the nature of controlling elements in maize and the manners of their operation.
One must await the right time for conceptual change. Following Jacob and Monod's Journal of Molecular Biology paper "Genetic regulatory mechanisms in the synthesis of proteins", McClintock wrote an article for American Naturalist comparing the lac operon and her work on controlling elements in maize.
Ac is a complete transposon that can produce a functional transposasewhich is required for the element to move within the genome. Ds has a mutation in its transposase gene, which means that it cannot move without another source of transposase. Thus, as McClintock observed, Ds cannot move in the absence of Ac.
Spm has also been characterized as a transposon. Subsequent research has shown that transposons typically do not move unless the cell is placed under stress, such as by irradiation or the breakage-fusion-bridge cycleand thus their activation during stress can serve as a source of genetic variation for evolution. Rosensteil Award in Inshe was awarded the Louisa Gross Horwitz Prize from Columbia University for her research in the "evolution of genetic information and the control of its expression.
She was compared to Gregor Mendel in terms of her scientific career by the Swedish Academy of Sciences when she was awarded the Prize. During her final years, McClintock led a more public life, especially after Evelyn Fox Keller 's biography of her, A Feeling for the Organism, brought McClintock's story to the public.
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She remained a regular presence in the Cold Spring Harbor community, and gave talks on mobile genetic elements and the history of genetics research for the benefit of junior scientists. McClintock died of natural causes in HuntingtonNew Yorkon September 2, at the age of 90; she never married or had children.
Comfort 's The Tangled Field: Comfort's biography contests some claims about McClintock, described as the "McClintock Myth", which he claims was perpetuated by the earlier biography by Keller. Keller's thesis was that McClintock was long ignored or met with derision because she was a woman working in the sciences. For example, when McClintock presented her findings that the genetics of maize did not conform to Mendelian distributions, geneticist Sewall Wright expressed the belief that she did not understand the underlying mathematics of her work, a belief he had expressed towards other women at the time.
She was intolerant of arrogance She felt she had crossed a desert alone and no one had followed her. Most recent biographical works on women in science feature accounts of her experience.
A recent biography for young adults by Naomi Pasachoff, Barbara McClintock, Genius of Genetics, provides a new perspective, based on the current literature. Intensive research has advanced our understanding about the biological principles underlying diverging RFI in pigs [ 2 — 5 ].
One factor that may contribute to diverging RFI in pigs is the digestive efficiency as well as nutrient demands for the intestinal mucosal immune response and integrity [ 2 — 5 ].
The extent of intestinal nutrient uptake greatly relies on the interplay between digestive secretions, the intestinal absorptive surface and the permeability of the intestinal epithelium [ 67 ].
More feed efficient animals consume less feed based on their growth and maintenance requirements [ 8 ]. Since the FI substantially influences the size and energy requirement of the intestine to degrade the ingested feed [ 9 — 11 ], more feed efficient animals should have a smaller GIT and hence lower energy demands for basal maintenance of the GIT [ 2 ].
Moreover, the mucosal integrity is important to consider with respect to translocation of intestinal antigens, thereby triggering energetically costly immune responses and affecting growth efficiency [ 57 ].
Previous findings for RFI-related differences in GIT size, innate immune response and digestive efficiency in pigs were equivocal [ 2 — 51213 ].
Some studies reported an enhanced ileal digestibility of energy and expression of SGLT1 and GLUT2 in the jejunum of growing pigs [ 314 ], whereas other did not find RFI-related differences for digestive efficiency [ 212 ].
Likewise, gene expression data indicated that the ileal mucosal tight-junction-protein expression and innate immune signaling pathways may play a minor role for variation in RFI of pigs in an unchallenged condition [ 45 ].
However, serum acute-phase-proteins and ileal inflammation markers indicated a stronger immune response in high compared to low RFI pigs [ 5 ].
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To date, most research regarding the impact of the gastrointestinal tract GIT on variation in RFI has been conducted under controlled conditions in one environment [ 2 — 413 ], whereby differences in environment, pig age, diet type and selection strategies for RFI used in the different studies may explain the controversial findings [ 15 ].
Therefore, we hypothesized that if the size, structure and functionality of the GIT play a role in variation of the RFI in pigs, similar RFI-relationships should be found in low and high RFI pigs which were raised under similar conditions in several environments.
The present objective was to investigate the differences in visceral organ size, intestinal structure, mucosal enzyme activity in duodenum, as well as jejunal mucosal integrity and gene expression of nutrient transporters, tight-junction proteins and components of the innate immune response in low and high RFI pigs which were raised at three different locations. Materials and methods Animal procedures and selection for feed efficiency Three pig experiments were conducted at three different research facilities using similar terminal sires, feeding and management protocols, comprising the experimental design, data and sample collection: For the pig trial in AT, all animal experimentation procedures were approved by the institutional ethics committee of the University of Veterinary Medicine Vienna, Austria and the national authority according to paragraph 26 of Law for Animal Experiments, Tierversuchsgesetz —TVG GZ In order to reduce the impact of the sire on FE of the progeny, sows were randomly inseminated with semen from boars Hermitage Genetics, Kilkenny, Ireland which had a high estimated breeding value for feed conversion efficiency.
One common boar was used at all locations in combination with 3 boars being specific for AT, 3 boars specific for NI and 10 boars specific for ROI. Sows were fed similar diet formulations gestation and lactation diets, S1 Table. Pigs were weaned at 28 days of age. Pigs were fed with the same sequence of diets with the same ingredient composition and chemical composition starter, link, weaner and finisher, S1 Table across locations via Feed Intake Recording Equipment FIRE feeders Schauer Agrotonic, Wels, Austria.
Water and feed were freely available throughout the nursery and fattening phases. At each location, pigs were placed on test between day 42 and 91 postweaning when intake was recorded daily and pig weight as well as back-fat depth was recorded weekly.
Following this test period day 91 postweaning RFI was calculated for each pig following which pigs were ranked according to their RFI. Pigs with extreme RFI were selected within litter and sex. For extreme animals of the same sex within a litter to be selected, their RFI had to be greater than two standard deviations distant from the mean of the two RFI ranks.
Visceral organ sampling Pigs had free access to feed until slaughter approximately day postweaning, see Supporting Information and were weighed before slaughter. At slaughter, the abdominal cavity was opened and the visceral organs including the gastrointestinal tract, liver, lungs, and kidneys were removed. Weight of liver, lungs and kidneys were recorded at all three locations.
Length and empty weight of the small intestine and cecum were measured only at AT. In AT, the small intestine and cecum were emptied of digesta, cleaned with water or, for intestinal segments where tissue samples were taken, with phosphate-buffered saline PBScleared of fat and connective tissue, blotted dry on paper towel and weighed. To account for BW differences among pigs, weight of the visceral organs and intestinal length were expressed per kg of BW.
Histological measurements Intestinal tissue samples for histological measurements were collected in AT and ROI, whereby duodenal, ileal and cecal tube samples were collected at both locations and jejunal tube samples only in AT.
Intestinal tube samples 2—3 cm in length were taken from the duodenum 15 cm distal from the pyloric junctionjejunum 2. Intestinal tube pieces were washed with PBS until all digesta were removed. Tube pieces were immediately placed in neutral-buffered pH 7.
After fixation in formalin for 48 h at AT, intestinal tube samples were dehydrated, cleared and embedded in paraffin. For each trait, 15 measurements were taken from intact well-oriented, crypt-villus units.