genetic factors
Both environmental and genetic factors have roles in the development of any disease. A genetic disorder is a disease caused by abnormalities in an individual’s genetic material (genome). The four different types of genetic disorders are(1) single-gene, (2) multifactorial, (3) chromosomal, and (4) mitochondrial.
genes
Genes generally express their functional effect through the production of proteins, which are complex molecules responsible for most functions in the cell. Proteins are chains of amino acids, and the DNA sequence of a gene (through RNA intermediate) is used to produce a specific protein sequence. This process begins with the production of an RNA molecule with a sequence matching the gene's DNA sequence, a process called transcription.
authors
^ Griffiths et al. (2000), Chapter 1 (Genetics and the Organism): Introduction
^ Hartl D, Jones E (2005)
^ Weiling F (1991). "Historical study: Johann Gregor Mendel 1822–1884". American Journal of Medical Genetics 40 (1): 1–25; discussion 26. doi:10.1002/ajmg.1320400103. PMID 1887835.
^ Lamarck, J-B (2008). In Encyclopædia Britannica. Retrieved from Encyclopædia Britannica Online on 2008-03-16.
^ a b Mendel, GJ (1866). "Versuche über Pflanzen-Hybriden". Verhandlungen des naturforschenden Vereins Brünn 4: 3–47. (in English in 1901, J. R. Hortic. Soc. 26: 1–32) translation available online
^ genetics, n., Oxford English Dictionary, 3rd ed.
^ Bateson W. Letter from William Bateson to Alan Sedgwick in 1905. The John Innes Centre. Retrieved on 2008-03-15.
^ genetic, adj., Oxford English Dictionary, 3rd ed.
^ Bateson, W (1907). "The Progress of Genetic Research". Wilks, W (editor) Report of the Third 1906 International Conference on Genetics: Hybridization (the cross-breeding of genera or species), the cross-breeding of varieties, and general plant breeding, London: Royal Horticultural Society.
Although the conference was titled "International Conference on Hybridisation and Plant Breeding", Wilks changed the title for publication as a result of Bateson's speech.
^ Moore JA (1983). "Thomas Hunt Morgan—The Geneticist". American Zoologist 23 (4): 855–865. doi:10.1093/icb/23.4.855.
^ Sturtevant AH (1913). "The linear arrangement of six sex-linked factors in Drosophila, as shown by their mode of association". Journal of Experimental Biology 14: 43–59. pdf from Electronic Scholarly Publishing
^ Avery OT, MacLeod CM, and McCarty M (1944). "Studies on the Chemical Nature of the Substance Inducing Transformation of Pneumococcal Types: Induction of Transformation by a Desoxyribonucleic Acid Fraction Isolated from Pneumococcus Type III". Journal of Experimental Medicine 79 (1): 137–158. doi:10.1084/jem.79.2.137. 35th anniversary reprint available
^ Hershey AD, Chase M (1952). "Independent functions of viral protein and nucleic acid in growth of bacteriophage". The Journal of General Physiology 36: 39–56. doi:10.1085/jgp.36.1.39. PMID 12981234.
^ Judson, Horace (1979). The Eighth Day of Creation: Makers of the Revolution in Biology. Cold Spring Harbor Laboratory Press, 51–169. ISBN 0-87969-477-7.
^ Watson JD, Crick FHC (1953). "Molecular structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid" (PDF). Nature 171 (4356): 737–738. doi:10.1038/171737a0.
^ Watson JD, Crick FHC (1953). "Genetical Implications of the Structure of Deoxyribonucleic Acid" (PDF). Nature 171 (4361): 964–967. doi:10.1038/171964b0.
^ Sanger F, Nicklen S, and Coulson AR (1977). "DNA sequencing with chain-terminating inhibitors". Nature 74 (12): 5463–5467. doi:10.1073/pnas.74.12.5463. PMID 271968.
^ Saiki RK, Scharf S, Faloona F, Mullis KB, Horn GT, Erlich HA, Arnheim N (1985). "Enzymatic Amplification of β-Globin Genomic Sequences and Restriction Site Analysis for Diagnosis of Sickle Cell Anemia". Science 230 (4732): 1350–1354. doi:10.1126/science.2999980. PMID 2999980.
^ a b Human Genome Project Information. Human Genome Project. Retrieved on 2008-03-15.
^ Griffiths et al. (2000), Chapter 2 (Patterns of Inheritance): Introduction
^ Griffiths et al. (2000), Chapter 2 (Patterns of Inheritance): Mendel's experiments
^ Griffiths et al. (2000), Chapter 3 (Chromosomal Basis of Heredity): Mendelian genetics in eukaryotic life cycles
^ Griffiths et al. (2000), Chapter 4 (Gene Interaction): Interactions between the alleles of one gene
^ Richard W. Cheney. Genetic Notation. Retrieved on 2008-03-18.
^ Griffiths et al. (2000), Chapter 2 (Patterns of Inheritance): Human Genetics
^ Griffiths et al. (2000), Chapter 4 (Gene Interaction): Gene interaction and modified dihybrid ratios
^ Mayeux R (2005). "Mapping the new frontier: complex genetic disorders". The Journal of Clinical Investigation 115 (6): 1404–1407. doi:10.1172/JCI25421. PMID 15931374.
^ Griffiths et al. (2000), Chapter 25 (Quantitative Genetics): Quantifying heritability
^ Luke A, Guo X, Adeyemo AA, Wilks R, Forrester T, Lowe W Jr, Comuzzie AG, Martin LJ, Zhu X, Rotimi CN, Cooper RS (2001). "Heritability of obesity-related traits among Nigerians, Jamaicans and US black people". Int J Obes Relat Metab Disord 25 (7): 1034–1041. doi:10.1038/sj.ijo.0801650. Abstract from NCBI
^ Pearson H (2006). "Genetics: what is a gene?". Nature 441 (7092): 398–401. doi:10.1038/441398a. PMID 16724031.
^ Prescott, L (1993). Microbiology. Wm. C. Brown Publishers. 0-697-01372-3.
^ Griffiths et al. (2000), Chapter 8 (The Structure and Replication of DNA): Mechanism of DNA Replication
^ Gregory SG et al. (2006). "The DNA sequence and biological annotation of human chromosome 1". Nature 441: 315–321. doi:10.1038/nature04727. free full text available
^ Alberts et al. (2002), DNA and chromosomes: Chromosomal DNA and Its Packaging in the Chromatin Fiber
^ a b Griffiths et al. (2000), Chapter 3 (Chromosomal Basis of Heredity): Mendelian genetics in eukaryotic life cycles
^ Griffiths et al. (2000), Chapter 2 (Patterns of Inheritance): Sex chromosomes and sex-linked inheritance
^ Griffiths et al. (2000), Chapter 7 (Gene Transfer in Bacteria and Their Viruses): Bacterial conjugation
^ Griffiths et al. (2000), Chapter 7 (Gene Transfer in Bacteria and Their Viruses): Bacterial transformation
^ Griffiths et al. (2000), Chapter 5 (Basic Eukaryotic Chromosome Mapping): Nature of crossing-over
^ Griffiths et al. (2000), Chapter 5 (Basic Eukaryotic Chromosome Mapping): Linkage maps
^ Berg JM, Tymoczko JL, Stryer L, Clarke ND (2002). Biochemistry, 5th edition, New York: W. H. Freeman and Company. I. 5. DNA, RNA, and the Flow of Genetic Information: Amino Acids Are Encoded by Groups of Three Bases Starting from a Fixed Point
^ Crick, F (1970): Central Dogma of Molecular Biology (PDF). Nature 227, 561–563. PMID 4913914
^ Alberts et al. (2002), Proteins: The Shape and Structure of Proteins
^ Alberts et al. (2002), Proteins: Protein Function
^ How Does Sickle Cell Cause Disease?. Brigham and Women's Hospital: Information Center for Sickle Cell and Thalassemic Disorders (2002-04-11). Retrieved on 2007-07-23.
^ Imes DL, Geary LA, Grahn RA, Lyons LA (2006). "Albinism in the domestic cat (Felis catus) is associated with a tyrosinase (TYR) mutation" (Short Communication). Animal Genetics 37 (2): 175. doi:10.1111/j.1365-2052.2005.01409.x. Retrieved on 2006-05-29.
^ MedlinePlus: Phenylketonuria. NIH: National Library of Medicine. Retrieved on 2008-03-15.
^ Brivanlou AH, Darnell JE Jr (2002). "Signal transduction and the control of gene expression". Science 295 (5556): 813–818. doi:10.1126/science.1066355. PMID 11823631.
^ Alberts et al. (2002), Control of Gene Expression - The Tryptophan Repressor Is a Simple Switch That Turns Genes On and Off in Bacteria
^ Jaenisch R, Bird A. "Epigenetic regulation of gene expression: how the genome integrates intrinsic and environmental signals". Nature Genetics 33 (3s): 245–254. doi:10.1038/ng1089.
^ Chandler VL (2007). "Paramutation: From Maize to Mice". Cell 128: 641–645. doi:10.1016/j.cell.2007.02.007.
^ Griffiths et al. (2000), Chapter 16 (Mechanisms of Gene Mutation): Spontaneous mutations
^ Kunkel TA (2004). "DNA Replication Fidelity". Journal of Biological Chemistry 279 (17): 16895–16898. doi:10.1038/sj.emboj.7600158.
^ Griffiths et al. (2000), Chapter 16 (Mechanisms of Gene Mutation): Induced mutations
^ Griffiths et al. (2000), Chapter 17 (Chromosome Mutation I: Changes in Chromosome Structure): Introduction
^ Griffiths et al. (2000), Chapter 24 (Population Genetics): Variation and its modulation
^ Griffiths et al. (2000), Chapter 24 (Population Genetics): Selection
^ Griffiths et al. (2000), Chapter 24 (Population Genetics): Random events
^ Darwin, Charles (1859). On the Origin of Species, 1st, John Murray, 1. . Related earlier ideas were acknowledged in Darwin, Charles (1861). On the Origin of Species, 3rd, John Murray, xiii.
^ Gavrilets S (2003). "Perspective: models of speciation: what have we learned in 40 years?". Evolution 57 (10): 2197–2215. doi:10.1554/02-727. PMID 14628909.
^ Wolf YI, Rogozin IB, Grishin NV, Koonin EV (2002). "Genome trees and the tree of life". Trends Genet. 18 (9): 472–479. doi:10.1016/S0168-9525(02)02744-0. PMID 12175808.
^ The Use of Model Organisms in Instruction. University of Wisconsin: Wisconsin Outreach Research Modules. Retrieved on 2008-03-15.
^ NCBI: Genes and Disease. NIH: National Center for Biotechnology Information. Retrieved on 2008-03-15.
^ Davey Smith, G; Ebrahim, S (2003). "‘Mendelian randomization’: can genetic epidemiology contribute to understanding environmental determinants of disease?". International Journal of Epidemiology 32: 1–22. doi:10.1093/ije/dyg070. PMID 12689998.
^ Pharmacogenetics Fact Sheet. NIH: National Institute of General Medical Sciences. Retrieved on 2008-03-15.
^ Strachan T, Read AP (1999). Human Molecular Genetics 2, second edition, John Wiley & Sons Inc.. Chapter 18: Cancer Genetics
^ Lodish et al. (2000), Chapter 7: 7.1. DNA Cloning with Plasmid Vectors
^ Lodish et al. (2000), Chapter 7: 7.7. Polymerase Chain Reaction: An Alternative to Cloning
^ Brown TA (2002). Genomes 2, 2nd edition. ISBN ISBN 1 85996 228 9. Section 2, Chapter 6: 6.1. The Methodology for DNA Sequencing
^ Brown (2002), Section 2, Chapter 6: 6.2. Assembly of a Contiguous DNA Sequence
^ Hartl D, Jones E (2005)
^ Weiling F (1991). "Historical study: Johann Gregor Mendel 1822–1884". American Journal of Medical Genetics 40 (1): 1–25; discussion 26. doi:10.1002/ajmg.1320400103. PMID 1887835.
^ Lamarck, J-B (2008). In Encyclopædia Britannica. Retrieved from Encyclopædia Britannica Online on 2008-03-16.
^ a b Mendel, GJ (1866). "Versuche über Pflanzen-Hybriden". Verhandlungen des naturforschenden Vereins Brünn 4: 3–47. (in English in 1901, J. R. Hortic. Soc. 26: 1–32) translation available online
^ genetics, n., Oxford English Dictionary, 3rd ed.
^ Bateson W. Letter from William Bateson to Alan Sedgwick in 1905. The John Innes Centre. Retrieved on 2008-03-15.
^ genetic, adj., Oxford English Dictionary, 3rd ed.
^ Bateson, W (1907). "The Progress of Genetic Research". Wilks, W (editor) Report of the Third 1906 International Conference on Genetics: Hybridization (the cross-breeding of genera or species), the cross-breeding of varieties, and general plant breeding, London: Royal Horticultural Society.
Although the conference was titled "International Conference on Hybridisation and Plant Breeding", Wilks changed the title for publication as a result of Bateson's speech.
^ Moore JA (1983). "Thomas Hunt Morgan—The Geneticist". American Zoologist 23 (4): 855–865. doi:10.1093/icb/23.4.855.
^ Sturtevant AH (1913). "The linear arrangement of six sex-linked factors in Drosophila, as shown by their mode of association". Journal of Experimental Biology 14: 43–59. pdf from Electronic Scholarly Publishing
^ Avery OT, MacLeod CM, and McCarty M (1944). "Studies on the Chemical Nature of the Substance Inducing Transformation of Pneumococcal Types: Induction of Transformation by a Desoxyribonucleic Acid Fraction Isolated from Pneumococcus Type III". Journal of Experimental Medicine 79 (1): 137–158. doi:10.1084/jem.79.2.137. 35th anniversary reprint available
^ Hershey AD, Chase M (1952). "Independent functions of viral protein and nucleic acid in growth of bacteriophage". The Journal of General Physiology 36: 39–56. doi:10.1085/jgp.36.1.39. PMID 12981234.
^ Judson, Horace (1979). The Eighth Day of Creation: Makers of the Revolution in Biology. Cold Spring Harbor Laboratory Press, 51–169. ISBN 0-87969-477-7.
^ Watson JD, Crick FHC (1953). "Molecular structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid" (PDF). Nature 171 (4356): 737–738. doi:10.1038/171737a0.
^ Watson JD, Crick FHC (1953). "Genetical Implications of the Structure of Deoxyribonucleic Acid" (PDF). Nature 171 (4361): 964–967. doi:10.1038/171964b0.
^ Sanger F, Nicklen S, and Coulson AR (1977). "DNA sequencing with chain-terminating inhibitors". Nature 74 (12): 5463–5467. doi:10.1073/pnas.74.12.5463. PMID 271968.
^ Saiki RK, Scharf S, Faloona F, Mullis KB, Horn GT, Erlich HA, Arnheim N (1985). "Enzymatic Amplification of β-Globin Genomic Sequences and Restriction Site Analysis for Diagnosis of Sickle Cell Anemia". Science 230 (4732): 1350–1354. doi:10.1126/science.2999980. PMID 2999980.
^ a b Human Genome Project Information. Human Genome Project. Retrieved on 2008-03-15.
^ Griffiths et al. (2000), Chapter 2 (Patterns of Inheritance): Introduction
^ Griffiths et al. (2000), Chapter 2 (Patterns of Inheritance): Mendel's experiments
^ Griffiths et al. (2000), Chapter 3 (Chromosomal Basis of Heredity): Mendelian genetics in eukaryotic life cycles
^ Griffiths et al. (2000), Chapter 4 (Gene Interaction): Interactions between the alleles of one gene
^ Richard W. Cheney. Genetic Notation. Retrieved on 2008-03-18.
^ Griffiths et al. (2000), Chapter 2 (Patterns of Inheritance): Human Genetics
^ Griffiths et al. (2000), Chapter 4 (Gene Interaction): Gene interaction and modified dihybrid ratios
^ Mayeux R (2005). "Mapping the new frontier: complex genetic disorders". The Journal of Clinical Investigation 115 (6): 1404–1407. doi:10.1172/JCI25421. PMID 15931374.
^ Griffiths et al. (2000), Chapter 25 (Quantitative Genetics): Quantifying heritability
^ Luke A, Guo X, Adeyemo AA, Wilks R, Forrester T, Lowe W Jr, Comuzzie AG, Martin LJ, Zhu X, Rotimi CN, Cooper RS (2001). "Heritability of obesity-related traits among Nigerians, Jamaicans and US black people". Int J Obes Relat Metab Disord 25 (7): 1034–1041. doi:10.1038/sj.ijo.0801650. Abstract from NCBI
^ Pearson H (2006). "Genetics: what is a gene?". Nature 441 (7092): 398–401. doi:10.1038/441398a. PMID 16724031.
^ Prescott, L (1993). Microbiology. Wm. C. Brown Publishers. 0-697-01372-3.
^ Griffiths et al. (2000), Chapter 8 (The Structure and Replication of DNA): Mechanism of DNA Replication
^ Gregory SG et al. (2006). "The DNA sequence and biological annotation of human chromosome 1". Nature 441: 315–321. doi:10.1038/nature04727. free full text available
^ Alberts et al. (2002), DNA and chromosomes: Chromosomal DNA and Its Packaging in the Chromatin Fiber
^ a b Griffiths et al. (2000), Chapter 3 (Chromosomal Basis of Heredity): Mendelian genetics in eukaryotic life cycles
^ Griffiths et al. (2000), Chapter 2 (Patterns of Inheritance): Sex chromosomes and sex-linked inheritance
^ Griffiths et al. (2000), Chapter 7 (Gene Transfer in Bacteria and Their Viruses): Bacterial conjugation
^ Griffiths et al. (2000), Chapter 7 (Gene Transfer in Bacteria and Their Viruses): Bacterial transformation
^ Griffiths et al. (2000), Chapter 5 (Basic Eukaryotic Chromosome Mapping): Nature of crossing-over
^ Griffiths et al. (2000), Chapter 5 (Basic Eukaryotic Chromosome Mapping): Linkage maps
^ Berg JM, Tymoczko JL, Stryer L, Clarke ND (2002). Biochemistry, 5th edition, New York: W. H. Freeman and Company. I. 5. DNA, RNA, and the Flow of Genetic Information: Amino Acids Are Encoded by Groups of Three Bases Starting from a Fixed Point
^ Crick, F (1970): Central Dogma of Molecular Biology (PDF). Nature 227, 561–563. PMID 4913914
^ Alberts et al. (2002), Proteins: The Shape and Structure of Proteins
^ Alberts et al. (2002), Proteins: Protein Function
^ How Does Sickle Cell Cause Disease?. Brigham and Women's Hospital: Information Center for Sickle Cell and Thalassemic Disorders (2002-04-11). Retrieved on 2007-07-23.
^ Imes DL, Geary LA, Grahn RA, Lyons LA (2006). "Albinism in the domestic cat (Felis catus) is associated with a tyrosinase (TYR) mutation" (Short Communication). Animal Genetics 37 (2): 175. doi:10.1111/j.1365-2052.2005.01409.x. Retrieved on 2006-05-29.
^ MedlinePlus: Phenylketonuria. NIH: National Library of Medicine. Retrieved on 2008-03-15.
^ Brivanlou AH, Darnell JE Jr (2002). "Signal transduction and the control of gene expression". Science 295 (5556): 813–818. doi:10.1126/science.1066355. PMID 11823631.
^ Alberts et al. (2002), Control of Gene Expression - The Tryptophan Repressor Is a Simple Switch That Turns Genes On and Off in Bacteria
^ Jaenisch R, Bird A. "Epigenetic regulation of gene expression: how the genome integrates intrinsic and environmental signals". Nature Genetics 33 (3s): 245–254. doi:10.1038/ng1089.
^ Chandler VL (2007). "Paramutation: From Maize to Mice". Cell 128: 641–645. doi:10.1016/j.cell.2007.02.007.
^ Griffiths et al. (2000), Chapter 16 (Mechanisms of Gene Mutation): Spontaneous mutations
^ Kunkel TA (2004). "DNA Replication Fidelity". Journal of Biological Chemistry 279 (17): 16895–16898. doi:10.1038/sj.emboj.7600158.
^ Griffiths et al. (2000), Chapter 16 (Mechanisms of Gene Mutation): Induced mutations
^ Griffiths et al. (2000), Chapter 17 (Chromosome Mutation I: Changes in Chromosome Structure): Introduction
^ Griffiths et al. (2000), Chapter 24 (Population Genetics): Variation and its modulation
^ Griffiths et al. (2000), Chapter 24 (Population Genetics): Selection
^ Griffiths et al. (2000), Chapter 24 (Population Genetics): Random events
^ Darwin, Charles (1859). On the Origin of Species, 1st, John Murray, 1. . Related earlier ideas were acknowledged in Darwin, Charles (1861). On the Origin of Species, 3rd, John Murray, xiii.
^ Gavrilets S (2003). "Perspective: models of speciation: what have we learned in 40 years?". Evolution 57 (10): 2197–2215. doi:10.1554/02-727. PMID 14628909.
^ Wolf YI, Rogozin IB, Grishin NV, Koonin EV (2002). "Genome trees and the tree of life". Trends Genet. 18 (9): 472–479. doi:10.1016/S0168-9525(02)02744-0. PMID 12175808.
^ The Use of Model Organisms in Instruction. University of Wisconsin: Wisconsin Outreach Research Modules. Retrieved on 2008-03-15.
^ NCBI: Genes and Disease. NIH: National Center for Biotechnology Information. Retrieved on 2008-03-15.
^ Davey Smith, G; Ebrahim, S (2003). "‘Mendelian randomization’: can genetic epidemiology contribute to understanding environmental determinants of disease?". International Journal of Epidemiology 32: 1–22. doi:10.1093/ije/dyg070. PMID 12689998.
^ Pharmacogenetics Fact Sheet. NIH: National Institute of General Medical Sciences. Retrieved on 2008-03-15.
^ Strachan T, Read AP (1999). Human Molecular Genetics 2, second edition, John Wiley & Sons Inc.. Chapter 18: Cancer Genetics
^ Lodish et al. (2000), Chapter 7: 7.1. DNA Cloning with Plasmid Vectors
^ Lodish et al. (2000), Chapter 7: 7.7. Polymerase Chain Reaction: An Alternative to Cloning
^ Brown TA (2002). Genomes 2, 2nd edition. ISBN ISBN 1 85996 228 9. Section 2, Chapter 6: 6.1. The Methodology for DNA Sequencing
^ Brown (2002), Section 2, Chapter 6: 6.2. Assembly of a Contiguous DNA Sequence
References
Alberts B, Johnson A, Lewis J, Raff M, Roberts K, and Walter P (2002). Molecular Biology of the Cell, 4th edition. ISBN 0-8153-3218-1.
Griffiths AJF, Miller JH, Suzuki DT, Lewontin RC, and Gelbart WM (2000). An Introduction to Genetic Analysis. New York: W.H. Freeman and Company. ISBN 0-7167-3520-2.
Hartl D, Jones E (2005). Genetics: Analysis of Genes and Genomes, 6th edition. Jones & Bartlett. ISBN 0-7637-1511-5.
Lodish H, Berk A, Zipursky LS, Matsudaira P, Baltimore D, and Darnell J (2000). Molecular Cell Biology, 4th edition. ISBN 0-7167-3136-3.
articles
Main articles: Asexual reproduction and Sexual reproduction
When cells divide, their full genome is copied and each daughter cell inherits one copy. This process, called mitosis, is the simplest form of reproduction and is the basis for asexual reproduction. Asexual reproduction can also occur in multicellular organisms, producing offspring that inherit their genome from a single parent. Offspring that are genetically identical to their parents are called clones.
When cells divide, their full genome is copied and each daughter cell inherits one copy. This process, called mitosis, is the simplest form of reproduction and is the basis for asexual reproduction. Asexual reproduction can also occur in multicellular organisms, producing offspring that inherit their genome from a single parent. Offspring that are genetically identical to their parents are called clones.
Interactions of multiple genes
Human height is a complex genetic trait. Francis Galton's data from 1889 shows the relationship between offspring height as a function of mean parent height. While correlated, remaining variation in offspring heights indicates environment is also an important factor in this trait.
Organisms have thousands of genes, and in sexually reproducing organisms assortment of these genes are generally independent of each other. This means that the inheritance of an allele for yellow or green pea color is unrelated to the inheritance of alleles for white or purple flowers. This phenomenon, known as "Mendel's second law" or the "Law of independent assortment", means that the alleles of different genes get shuffled between parents to form offspring with many different combinations. (Some genes do not assort independently, demonstrating genetic linkage, a topic discussed later in this article.)
Often different genes can interact in a way that influences the same trait. In the Blue-eyed Mary (Omphalodes verna), for example, there exists a gene with alleles that determine the color of flowers: blue or magenta. Another gene, however, controls whether the flowers have color at all: color or white. When a plant has two copies of this white allele, its flowers are white—regardless of whether the first gene has blue or magenta alleles. This interaction between genes is called epistasis, with the second gene epistatic to the first.[26]
Many traits are not discrete features (eg. purple or white flowers) but are instead continuous features (eg. human height and skin color). These complex traits are the product of many genes.[27] The influence of these genes is mediated, to varying degrees, by the environment an organism has experienced. The degree to which an organism's genes contribute to a complex trait is called heritability.[28] Measurement of the heritability of a trait is relative—in a more variable environment, the environment has a bigger influence on the total variation of the trait. For example, human height is a complex trait with a heritability of 89% in the United States. In Nigeria, however, where people experience a more variable access to good nutrition and health care, height has a heritability of only 62%.[29]
Features of inheritance
Although genes were known to exist on chromosomes, (chromosomes are composed of both protein and DNA) scientists did not know which of these was responsible for inheritance. In 1928, Frederick Griffith discovered the phenomenon of transformation (see Griffith's experiment): dead bacteria could transfer genetic material to "transform" other still-living bacteria. Sixteen years later, in 1944, Oswald Theodore Avery, Colin McLeod and Maclyn McCarty identified the molecule responsible for transformation as DNA.[12] The Hershey-Chase experiment in 1952 also showed that DNA (rather than protein) was the genetic material of the viruses that infect bacteria, providing further evidence that DNA was the molecule responsible for inheritance.[13]
James D. Watson and Francis Crick solved the structure of DNA in 1953, using the X-ray crystallography work of Rosalind Franklin that indicated DNA had a helical structure (ie. shaped like a corkscrew).[14][15] Their double-helix model had two strands of DNA with the nucleotides pointing inwards, each matching a complementary nucleotide on the other strand to form what looks like rungs on a twisted ladder.[16] This structure showed that genetic information exists in the sequence of nucleotides on each strand of DNA. The structure also suggested a simple method for duplication: if the strands are separated, new partner strands can be reconstructed for each based on the sequence of the old strand.
Although the structure of DNA showed how inheritance worked, it was still not known how DNA influenced the behavior of cells. In the following years scientists tried to understand how DNA controls the process of protein production. It was discovered that the cell uses DNA as a template to create matching messenger RNA (a molecule with nucleotides, very similar to DNA). The nucleotide sequence of a messenger RNA is used to create an amino acid sequence in protein; this translation between nucleotide and amino acid sequences is known as the genetic code.
With this molecular understanding of inheritance, an explosion of research became possible. One important development was chain-termination DNA sequencing in 1977 by Frederick Sanger: this technology allows scientists to read the nucleotide sequence of a DNA molecule.[17] In 1983 the polymerase chain reaction was developed by Kary Banks Mullis, providing a quick way to isolate and amplify a specific section of a DNA from a mixture.[18] These and other techniques, through the pooled efforts of the Human Genome Project and parallel private effort by Celera Genomics, culminated in the sequencing of the human genome in 2003.[19]
Features of inheritance
At its most fundamental level, inheritance in organisms occurs by means of discrete traits, called genes.[20] This property was first observed by Gregor Mendel, who studied the segregation of heritable traits in pea plants.[5][21] In his experiments studying the trait for flower color, Mendel observed that the flowers of each pea plant were either purple or white—and never an intermediate between the two colors. These different, discrete versions of the same gene are called alleles.
In the case of pea plants, each organism has two alleles of each gene, and the plants inherit one allele from each parent.[22] Many organisms, including humans, have this pattern of inheritance. Organisms with two copies of the same allele are called homozygous, while organisms with two different alleles are heterozygous.
The set of alleles for a given organism is called its genotype, while the observable trait the organism has is called its phenotype. When organisms are heterozygous, often one allele is called dominant as its qualities dominate the phenotype of the organism, while the other allele is called recessive as its qualities recede and are not observed. Some alleles do not have complete dominance and instead have incomplete dominance by expressing an intermediate phenotype, or codominance by expressing both alleles at once.[23]
When a pair of organisms reproduce sexually, their offspring randomly inherit one of the two alleles from each parent. These observations of discrete inheritance and the segregation of alleles are collectively known as Mendel's first law or the Law of Segregation.
James D. Watson and Francis Crick solved the structure of DNA in 1953, using the X-ray crystallography work of Rosalind Franklin that indicated DNA had a helical structure (ie. shaped like a corkscrew).[14][15] Their double-helix model had two strands of DNA with the nucleotides pointing inwards, each matching a complementary nucleotide on the other strand to form what looks like rungs on a twisted ladder.[16] This structure showed that genetic information exists in the sequence of nucleotides on each strand of DNA. The structure also suggested a simple method for duplication: if the strands are separated, new partner strands can be reconstructed for each based on the sequence of the old strand.
Although the structure of DNA showed how inheritance worked, it was still not known how DNA influenced the behavior of cells. In the following years scientists tried to understand how DNA controls the process of protein production. It was discovered that the cell uses DNA as a template to create matching messenger RNA (a molecule with nucleotides, very similar to DNA). The nucleotide sequence of a messenger RNA is used to create an amino acid sequence in protein; this translation between nucleotide and amino acid sequences is known as the genetic code.
With this molecular understanding of inheritance, an explosion of research became possible. One important development was chain-termination DNA sequencing in 1977 by Frederick Sanger: this technology allows scientists to read the nucleotide sequence of a DNA molecule.[17] In 1983 the polymerase chain reaction was developed by Kary Banks Mullis, providing a quick way to isolate and amplify a specific section of a DNA from a mixture.[18] These and other techniques, through the pooled efforts of the Human Genome Project and parallel private effort by Celera Genomics, culminated in the sequencing of the human genome in 2003.[19]
Features of inheritance
At its most fundamental level, inheritance in organisms occurs by means of discrete traits, called genes.[20] This property was first observed by Gregor Mendel, who studied the segregation of heritable traits in pea plants.[5][21] In his experiments studying the trait for flower color, Mendel observed that the flowers of each pea plant were either purple or white—and never an intermediate between the two colors. These different, discrete versions of the same gene are called alleles.
In the case of pea plants, each organism has two alleles of each gene, and the plants inherit one allele from each parent.[22] Many organisms, including humans, have this pattern of inheritance. Organisms with two copies of the same allele are called homozygous, while organisms with two different alleles are heterozygous.
The set of alleles for a given organism is called its genotype, while the observable trait the organism has is called its phenotype. When organisms are heterozygous, often one allele is called dominant as its qualities dominate the phenotype of the organism, while the other allele is called recessive as its qualities recede and are not observed. Some alleles do not have complete dominance and instead have incomplete dominance by expressing an intermediate phenotype, or codominance by expressing both alleles at once.[23]
When a pair of organisms reproduce sexually, their offspring randomly inherit one of the two alleles from each parent. These observations of discrete inheritance and the segregation of alleles are collectively known as Mendel's first law or the Law of Segregation.
science of genetics
Although the science of genetics began with the work of Gregor Mendel in the mid-1800s, there were some theories of inheritance that preceded Mendel. A popular theory during Mendel's time was the concept of blending inheritance: the idea that individuals inherit a smooth blend of traits from their parents. Mendel's work disproved this, showing that traits are composed of combinations of distinct genes rather than a continuous blend. Also popular at the time was the theory of inheritance of acquired characteristics: the belief that individuals inherit traits that have been strengthened in their parents. This theory (commonly associated with Jean-Baptiste Lamarck) is now known to be wrong, the experiences of individuals do not affect the genes they pass to their children.
dna
DNA, the molecular basis for inheritance. Each strand of DNA is a chain of nucleotides, matching each other in the center to form what look like rungs on a twisted ladder.
Genes correspond to regions within DNA, a molecule composed of a chain of four different types of nucleotides—the sequence of these nucleotides is the genetic information organisms inherit. DNA naturally occurs in a double stranded form, with nucleotides on each strand complementary to each other. Each strand can act as a template for creating a new partner strand—this is the physical method for making copies of genes that can be inherited.
Genes correspond to regions within DNA, a molecule composed of a chain of four different types of nucleotides—the sequence of these nucleotides is the genetic information organisms inherit. DNA naturally occurs in a double stranded form, with nucleotides on each strand complementary to each other. Each strand can act as a template for creating a new partner strand—this is the physical method for making copies of genes that can be inherited.
About the Author
Ray Burton is a motivational speaker, an ISSA-certified personal trainer, philanthropist, and author of the best selling weight loss book Fat To Fit - The Journey
discipline
Genetics, a discipline of biology, is the science of heredity and variation in living organisms.[1][2] The fact that living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding. However, the modern science of genetics, which seeks to understand the process of inheritance, only began with the work of mendel in the mid-nineteenth century.[3] Although he did not know the physical basis for heredity, Mendel observed that organisms inherit traits in a discrete manner—these basic units of inheritance are now called genes
genetics info
Genetics And Weight Loss
“I would be able to lose weight if it wasn’t for my genetics”
The actual truth is that genetic factors CAN play a role in the speed of weight loss. Why is this? Because from birth everyone has a different hormonal profile and hormones are what determine every action in the body. This includes metabolism and fat burning.
Now while genetic factors can play a role in the speed of weight loss, they cannot stop you from losing weight and changing your metabolism. Hormonal profiles can be changed! If your hormonal profile can be changed, then the speed of which you lose weight can be changed!
The point is that sometimes in the beginning, getting the weight loss machine humming can be some work. The last thing you need is to feel that all your efforts are in vain because you are fighting genetics.
What I want you to know is that genetics will only keep you fat if you do nothing in an effort to change it. Fat is very timid. As soon as you make an effort to change your physical state, your body will start to respond in kind. You start taking care of yourself and fat gets scared. You keep taking care of yourself and fat doesn’t feel comfortable hanging around.
Everybody can and will lose fat if they just try. Genetics just dictates the speed that everything happens at in the beginning.
Are some people naturally big? Yes, they are called endomorphs. Are some people naturally skinny? Yes, they are called ectomorphs. It doesn’t matter one lick though. Why? Because there are many things in life that people do not start out naturally gifted at but go on to become the best of the best through simply trying and never giving up.
What you can conceive, you can achieve.
I want to share with you some thoughts about thoughts. This is based around some motivational stuff I read from James Allen.
A woman’s mind may be likened to a garden, which may be lovingly cultivated or allowed to run wild; but whether cultivated or neglected, it must, and will, create. If no useful seeds are put into it, then an abundance of useless weeds will grow therein, and will continue to produce their kind.
Just as a gardener cultivates her plot, keeping it free from weeds, while growing the flowers and fruits which she requires, so may a woman tend the garden of her mind, weeding out all the negative, useless, and untrue thoughts, and cultivating toward perfection the flowers and fruits of positive, useful, and true thoughts. By pursuing this process, a woman sooner or later discovers that she is the master-gardener of her soul, the director of her life and body. She also reveals, within herself, the laws of thought, and understands, with ever-increasing accuracy, how the thoughts and mind elements operate in the shaping of her character, circumstances, and body.
What I want you to know is that the first step to getting the body you want and losing extra weight comes from letting go of who you think you are. You are not someone fighting the uphill battle against genetics. You are someone that needs to clear some weeds and get to work on a wonderful new creation.
“I would be able to lose weight if it wasn’t for my genetics”
The actual truth is that genetic factors CAN play a role in the speed of weight loss. Why is this? Because from birth everyone has a different hormonal profile and hormones are what determine every action in the body. This includes metabolism and fat burning.
Now while genetic factors can play a role in the speed of weight loss, they cannot stop you from losing weight and changing your metabolism. Hormonal profiles can be changed! If your hormonal profile can be changed, then the speed of which you lose weight can be changed!
The point is that sometimes in the beginning, getting the weight loss machine humming can be some work. The last thing you need is to feel that all your efforts are in vain because you are fighting genetics.
What I want you to know is that genetics will only keep you fat if you do nothing in an effort to change it. Fat is very timid. As soon as you make an effort to change your physical state, your body will start to respond in kind. You start taking care of yourself and fat gets scared. You keep taking care of yourself and fat doesn’t feel comfortable hanging around.
Everybody can and will lose fat if they just try. Genetics just dictates the speed that everything happens at in the beginning.
Are some people naturally big? Yes, they are called endomorphs. Are some people naturally skinny? Yes, they are called ectomorphs. It doesn’t matter one lick though. Why? Because there are many things in life that people do not start out naturally gifted at but go on to become the best of the best through simply trying and never giving up.
What you can conceive, you can achieve.
I want to share with you some thoughts about thoughts. This is based around some motivational stuff I read from James Allen.
A woman’s mind may be likened to a garden, which may be lovingly cultivated or allowed to run wild; but whether cultivated or neglected, it must, and will, create. If no useful seeds are put into it, then an abundance of useless weeds will grow therein, and will continue to produce their kind.
Just as a gardener cultivates her plot, keeping it free from weeds, while growing the flowers and fruits which she requires, so may a woman tend the garden of her mind, weeding out all the negative, useless, and untrue thoughts, and cultivating toward perfection the flowers and fruits of positive, useful, and true thoughts. By pursuing this process, a woman sooner or later discovers that she is the master-gardener of her soul, the director of her life and body. She also reveals, within herself, the laws of thought, and understands, with ever-increasing accuracy, how the thoughts and mind elements operate in the shaping of her character, circumstances, and body.
What I want you to know is that the first step to getting the body you want and losing extra weight comes from letting go of who you think you are. You are not someone fighting the uphill battle against genetics. You are someone that needs to clear some weeds and get to work on a wonderful new creation.
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