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Heredity

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Title: Heredity  
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Heredity

Heredity is the passing of species to evolve. The study of heredity in biology is called genetics, which includes the field of epigenetics.

Contents

  • Overview 1
  • Relation to theory of evolution 2
  • History 3
    • Gregor Mendel: father of genetics 3.1
    • Modern development of genetics and heredity 3.2
    • Common genetic disorders 3.3
  • Types of heredity 4
    • Dominant and recessive alleles 4.1
  • See also 5
  • Notes and references 6
  • External links 7

Overview

Heredity of phenotypic traits: Father and son with prominent ears and crowns.
DNA structure. Bases are in the centre, surrounded by phosphate–sugar chains in a double helix.

In humans, genome is called its genotype.[2]

The complete set of observable traits of the structure and behavior of an organism is called its suntanned skin comes from the interaction between a person's phenotype and sunlight;[4] thus, suntans are not passed on to people's children. However, some people tan more easily than others, due to differences in their genotype:[5] a striking example is people with the inherited trait of albinism, who do not tan at all and are very sensitive to sunburn.[6]

Heritable traits are known to be passed from one generation to the next via

  • Stanford Encyclopedia of Philosophy entry on Heredity and Heritability
  • ""Experiments in Plant Hybridization" (1866), by Johann Gregor Mendel," by A. Andrei at the Embryo Project Encyclopedia

External links

  1. ^ Sturm RA, Frudakis TN (2004). "Eye colour: portals into pigmentation genes and ancestry". Trends Genet. 20 (8): 327–32.  
  2. ^ a b Pearson H (2006). "Genetics: what is a gene?". Nature 441 (7092): 398–401.  
  3. ^ Visscher PM, Hill WG, Wray NR (2008). "Heritability in the genomics era—concepts and misconceptions". Nat. Rev. Genet. 9 (4): 255–66.  
  4. ^ Shoag J et al. (Jan 2013). "PGC-1 coactivators regulate MITF and the tanning response". Mol Cell 49 (1): 145–57.  
  5. ^ Pho LN, Leachman SA. (Feb 2010). "Genetics of pigmentation and melanoma predisposition". G Ital Dermatol Venereol. 145 (1): 37–45.  
  6. ^ Oetting WS, Brilliant MH, King RA (1996). "The clinical spectrum of albinism in humans". Molecular medicine today 2 (8): 330–5.  
  7. ^ Griffiths, Anthony, J. F.; Wessler, Susan R., Carroll, Sean B., Doebley J (2012). Introduction to Genetic Analysis (10 ed.). New York: W. H. Freeman and Company. p. 3.  
  8. ^  
  9. ^ Phillips PC (2008). "Epistasis—the essential role of gene interactions in the structure and evolution of genetic systems". Nat. Rev. Genet. 9 (11): 855–67.  
  10. ^ Wu R, Lin M (2006). "Functional mapping – how to map and study the genetic architecture of dynamic complex traits". Nat. Rev. Genet. 7 (3): 229–37.  
  11. ^ Jablonka, E.; Lamb, M. J. (2002). "The changing concept of epigenetics". Annals of the New York Academy of Sciences 981 (1): 82–96.  
  12. ^ Jablonka, E.; Raz, G. (2009). "Transgenerational epigenetic inheritance: Prevalence, mechanisms, and implications for the study of heredity and evolution". The Quarterly Review of Biology 84 (2): 131–176.  
  13. ^ Bossdorf, O.; Arcuri, D.; Richards, C. L.; Pigliucci, M. (2010). "Arabidopsis thaliana"Experimental alteration of DNA methylation affects the phenotypic plasticity of ecologically relevant traits in . Evolutionary Ecology 24 (3): 541–553.  
  14. ^ Jablonka, E.; Lamb, M. (2005). Evolution in four dimensions: Genetic, epigenetic, behavioural, and symbolic. MIT Press.  
  15. ^ Laland, K. N.; Sterelny, K. (2006). "Perspective: Seven reasons (not) to neglect niche construction". Evolution 60 (8): 1751–1762.  
  16. ^ Chapman, M. J.; Margulis, L. (1998). "Morphogenesis by symbiogenesis". International Microbiology 1 (4): 319–326.  
  17. ^ a b Wilson, D. S.; Wilson, E. O. (2007). "Rethinking the theoretical foundation of sociobiology". The Quarterly Review of Biology 82 (4): 327–48.  
  18. ^ Bijma, P.; Wade, M. J. (2008). "The joint effects of kin, multilevel selection and indirect genetic effects on response to genetic selection". Journal of Evolutionary Biology 21 (5): 1175–1188.  
  19. ^ Vrba, E. S.; Gould, S. J. (1986). "The hierarchical expansion of sorting and selection: Sorting and selection cannot be equated". Paleobiology 12 (2): 217–228. 
  20. ^ Griffiths, Anthony, J. F.; Wessler, Susan R.; Carroll, Sean B.; Doebley, John (2012). Introduction to Genetic Analysis (10 ed.). New York: W. H. Freeman and Company. p. 14.  
  21. ^ Charlesworth, Brian and Charlesworth, Deborah (November 2009). "Darwin and Genetics". Genetics November 2009 vol. 183 no. 3 757–766 183 (3): 757–766.  
  22. ^ Bard, Jonathan BL (2011). "The next evolutionary synthesis: from Lamarck and Darwin to genomic variation and systems biology". Cell Communication and Signaling 9 (30): 30.  
  23. ^ "Francis Galton (1822-1911)".  
  24. ^ Liu Y. (May 2008). "A new perspective on Darwin's Pangenesis". Biol Rev Camb Philos Soc. 83 (2): 141–9.  
  25. ^ Lipton, Bruce H. (2008). The Biology of Belief: Unleashing the Power of Consciousness, Matter and Miracles. Hay House, Inc. p. 12.  
  26. ^ Negbi, Moshe (Summer 1995). "Male and female in Theophrastus's botanical works". Journal of the History of Biology 28 (2): 317–332.  
  27. ^ Hipócrates (1981). Hippocratic Treatises: On Generation - Nature of the Child - Diseases Ic. Walter de Gruyter. p. 6.  
  28. ^ "Aristotle's Biology - 5.2. From Inquiry to Understanding; from hoti to dioti.". Stanford University. Feb 15, 2006. Retrieved March 26, 2013. 
  29. ^ Eumenides 658-661
  30. ^ Snow, Kurt. """Antoni van Leeuwenhoek's Amazing Little "Animalcules. Leben. Retrieved March 26, 2013. 
  31. ^ Lawrence, Cera R. (2008). Hartsoeker's Homunculus Sketch from Essai de Dioptrique. Embryo Project Encyclopedia.  
  32. ^ Gottlieb, Gilbert (2001). Individual Development and Evolution: The Genesis of Novel Behavior. Psychology Press. p. 4.  
  33. ^ Henig, Robin Marantz (2001). The Monk in the Garden : The Lost and Found Genius of Gregor Mendel, the Father of Genetics. Houghton Mifflin.  
  34. ^ a b Carlson, Neil and et al. Psychology the Science of Behavior, p. 206. Pearson Canada, United States of America. ISBN 978-0-205-64524-4.
  35. ^ Mayr & Provine 1998
  36. ^ Mayr E. 1982. The growth of biological thought: diversity, evolution & inheritance. Harvard, Cambs. p. 567 et seq.
  37. ^ Palumbi, Stephen R. (1994). "Genetic Divergence, Reproductive Isolation, and Marine Speciation". Annual Review of Ecology and Systematics 25: 547–572.  
  38. ^ Gould S. J. Ontogeny and phylogeny. Harvard 1977. p. 221–2
  39. ^ Handschuh, Stephan; Mitteroecker, Philipp (June 2012). "Evolution—The Extended Synthesis. A research proposal persuasive enough for the majority of evolutionary biologists?". The International Society for Human Ethology 27 (1–2): 18–21.  

Notes and references

See also

Determination and description of a mode of inheritance is achieved primarily through statistical analysis of pedigree data. In case the involved loci are known, methods of molecular genetics can also be employed.

6. Locus–locus interactions
5. Sex-linked interactions
4. Coincidental and environmental interactions

These three categories are part of every exact description of a mode of inheritance in the above order. In addition, more specifications may be added as follows:

3. Correlation genotypephenotype
2. Involved chromosomes
1. Number of involved loci

The description of a mode of biological inheritance consists of three main categories:

An allele is said to be dominant if it is always expressed in the appearance of an organism (phenotype) provided that at least one copy of it is present. For example, in peas the allele for green pods, G, is dominant to that for yellow pods, g. Thus pea plants with the pair of alleles either GG (homozygote) or Gg (heterozygote) will have green pods. The allele for yellow pods is recessive. The effects of this allele are only seen when it is present in both chromosomes, gg (homozygote).

Dominant and recessive alleles

An example pedigree chart of a sex-linked disorder (the gene is on the X chromosome)
An example pedigree chart of an autosomal recessive disorder.
An example pedigree chart of an autosomal dominant disorder.

Types of heredity

Common genetic disorders

Trofim Lysenko however caused a backlash of what is now called Lysenkoism in the Soviet Union when he emphasised Lamarckian ideas on the inheritance of acquired traits. This movement affected agricultural research and led to food shortages in the 1960s and seriously affected the USSR.

Almost all aspects of the synthesis have been challenged at times, with varying degrees of success. There is no doubt, however, that the synthesis was a great landmark in evolutionary biology.[39] It cleared up many confusions, and was directly responsible for stimulating a great deal of research in the post-World War II era.

The idea that speciation occurs after populations are reproductively isolated has been much debated.[37] In plants, polyploidy must be included in any view of speciation. Formulations such as 'evolution consists primarily of changes in the frequencies of alleles between one generation and another' were proposed rather later. The traditional view is that developmental biology ('evo-devo') played little part in the synthesis, but an account of Gavin de Beer's work by Stephen Jay Gould suggests he may be an exception.[38]

  1. All evolutionary phenomena can be explained in a way consistent with known genetic mechanisms and the observational evidence of naturalists.
  2. Evolution is gradual: small genetic changes, recombination ordered by natural selection. Discontinuities amongst species (or other taxa) are explained as originating gradually through geographical separation and extinction (not saltation).
  3. Selection is overwhelmingly the main mechanism of change; even slight advantages are important when continued. The object of selection is the phenotype in its surrounding environment. The role of genetic drift is equivocal; though strongly supported initially by Dobzhansky, it was downgraded later as results from ecological genetics were obtained.
  4. The primacy of population thinking: the genetic diversity carried in natural populations is a key factor in evolution. The strength of natural selection in the wild was greater than expected; the effect of ecological factors such as niche occupation and the significance of barriers to gene flow are all important.
  5. In palaeontology, the ability to explain historical observations by extrapolation from micro to macro-evolution is proposed. Historical contingency means explanations at different levels may exist. Gradualism does not mean constant rate of change.

In the 1930s, work by Fisher and others resulted in a combination of Mendelian and biometric schools into the modern evolutionary synthesis. The modern synthesis bridged the gap between experimental geneticists and naturalists; and between both and palaeontologists, stating that:[35][36]

Modern development of genetics and heredity

The idea of particulate inheritance of genes can be attributed to the Moravian[33] monk Gregor Mendel who published his work on pea plants in 1865. However, his work was not widely known and was rediscovered in 1901. It was initially assumed the Mendelian inheritance only accounted for large (qualitative) differences, such as those seen by Mendel in his pea plants—and the idea of additive effect of (quantitative) genes was not realised until R. A. Fisher's (1918) paper, "The Correlation Between Relatives on the Supposition of Mendelian Inheritance" Mendel's overall contribution gave scientists a useful overview that traits were inheritable. As of today, his pea plant demonstration became the foundation of the study of Mendelian Traits. These traits can be traced on a single locus.[34]

Table showing how the genes exchange according to segregation or independent assortment during meiosis and how this translates into Mendel's laws

Gregor Mendel: father of genetics

During the 18th century, Dutch microscopist Antonie van Leeuwenhoek (1632–1723) discovered "animalcules" in the sperm of humans and other animals.[30] Some scientists speculated they saw a "little man" (homunculus) inside each sperm. These scientists formed a school of thought known as the "spermists". They contended the only contributions of the female to the next generation were the womb in which the homunculus grew, and prenatal influences of the womb.[31] An opposing school of thought, the ovists, believed that the future human was in the egg, and that sperm merely stimulated the growth of the egg. Ovists thought women carried eggs containing boy and girl children, and that the gender of the offspring was determined well before conception.[32]

Various hereditary mechanisms were envisaged without being properly tested or quantified. These included blending inheritance and the inheritance of acquired traits. Nevertheless, people were able to develop domestic breeds of animals as well as crops through artificial selection. The inheritance of acquired traits also formed a part of early Lamarckian ideas on evolution.

Scientists in Antiquity had a variety of ideas about heredity: Theophrastus proposed that male flowers caused female flowers to ripen;[26] Hippocrates speculated that "seeds" were produced by various body parts and transmitted to offspring at the time of conception;[27] and Aristotle thought that male and female semen mixed at conception.[28] Aeschylus, in 458 BC, proposed the male as the parent, with the female as a "nurse for the young life sown within her".[29]

History

The inheritance of acquired traits was shown to have little basis in the 1880s when August Weismann cut the tails off many generations of mice and found that their offspring continued to develop tails.[25]

Darwin's initial model of heredity was adopted by, and then heavily modified by, his cousin Francis Galton, who laid the framework for the biometric school of heredity.[23] Galton found no evidence to support the aspects of Darwin's pangenesis model, which relied on acquired traits.[24]

When Charles Darwin proposed his theory of evolution in 1859, one of its major problems was the lack of an underlying mechanism for heredity.[20] Darwin believed in a mix of blending inheritance and the inheritance of acquired traits (pangenesis). Blending inheritance would lead to uniformity across populations in only a few generations and then would remove variation from a population on which natural selection could act.[21] This led to Darwin adopting some Lamarckian ideas in later editions of On the Origin of Species and his later biological works.[22] Darwin's primary approach to heredity was to outline how it appeared to work (noticing that traits that were not expressed explicitly in the parent at the time of reproduction could be inherited, that certain traits could be sex-linked, etc.) rather than suggesting mechanisms.

Relation to theory of evolution

[19][17], which has been a subject of intense debate in the history of evolutionary science.multilevel or hierarchical selection These examples of heritability that operate above the gene are covered broadly under the title of [18][17][16].symbiogenesis, and group heritability, cultural traits Other examples of heritability in evolution that are not under the direct control of genes include the inheritance of [15] Recent findings have confirmed important examples of heritable changes that cannot be explained by direct agency of the DNA molecule. These phenomena are classed as

[11].canalization and developmental plasticity Developmental biologists suggest that complex interactions in genetic networks and communication among cells can lead to heritable variations that may underlay some of the mechanics in [10][9] However, while this simple correspondence between an allele and a trait works in some cases, most traits are more complex and are controlled by

[8]

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