The Chromosomal Theory of Inheritance, proposed by Walter Sutton and Theodor Boveri in 1902-1903 is considered a landmark in the science of genetics (Martins, 1999). The theory established chromosomes as the carriers of hereditary information (genes). It also implied that chromosomes (and not genes) undergo segregation and independent assortment as proposed by Gregor Johann Medel (1865-1866) in his Laws of Inheritance. A chromosome can contain more than one gene(s). Although the contemporary scholars were highly skeptical of this idea, Thomas Hunt Morgan (1915), showed linear arrangement of genes in chromosomes providing a convincing evidence for Sutton-Boveri’s work. The aim of this essay is to investigate the structure of a chromosome and how external factors such as the environment and epigenetics causes alteration in its structure and therefore its function.
Chromosomes are only visible during the metaphase stage of cell division and are seen as condensed thread-like structures when observed under a microscope. Most of the time they are dispersed in the nucleus of a cell in the form of thin fibers, called chromatin. Chromosomes differ from chromatin due to the fact that they are more highly compact and coiled. Extensive study has been done on the structure of chromosome. (Ris & Kubai, 1970, Weintraub & Van Lente, 1974, Gillies, 1975, Paulson & Laemmli, 1977, Comings, 1978, Howell & Hsu, 1979, Marsden & Laemmli, 1979, Lima-de-Faria, 2003). It can be noted from these studies that chromosome structure varies greatly among viruses, prokaryotes and eukaryotes. Viral chromosomes are made of a nucleic acid surrounded by a protein coat while in prokaryotes they tend to be just a copy of a circular DNA molecule arranged in the nucleoid...
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Pilegaard, H., Ordway, G. A., Saltin, B., & Neufer, P. D. (2000). Transcriptional regulation of gene expression in human skeletal muscle during recovery from exercise. American Journal of Physiology-Endocrinology And Metabolism, 279(4), E806-E814. Retrieved from http://ajpendo.physiology.org/content/279/4/E806.short
Ris, H., & Kubai, D. F. (1970). Chromosome structure. Annual review of genetics, 4(1), 263-294. doi: 10.1146/annurev.ge.04.120170.001403
University of Tennesse (n.d.). Epigenesis and the epigenetic cascade. Retrieved May 3, 2014, from https://notes.utk.edu/Bio/greenberg.nsf/0 /f0820b0a18b7994185256d270047a586?OpenDocument
Weintraub, H., & Van Lente, F. (1974). Dissection of chromosome structure with trypsin and nucleases. Proceedings of the National Academy of Sciences,71(10), 4249-4253. doi: 10.1073/pnas.71.10.4249
Miller, Kenneth R. and Joseph S. Levine. “Chapter 12: DNA and RNA.” Biology. Upper Saddle River: Pearson Education, Inc., 2002. Print.
During interphase, the cells in both animals and bacteria carry out their division general functions according to the type of their cells. Unlike in plants, a preprophase group of cytoskeletal proteins emerge at a future location of the cell plate. At prophase stage, duplicated chromosomes compress in a way that can be seen with the help of a microscope. On the other hand, the mitotic spindle is formed at one side of nucleus, whereas in plants, spindle is formed around the nucleus. During prometaphase in animals and bacteria, the nuclear membrane disappears, the chromosomes attach themselves to mictotubules and start to move. In plants, however, the preprophase group dissolves while at metaphase stage, the chromosomes get aligned at the core of the cell. At anaphase, there are fewer differences between animals and plants. The chromosomes shift apart towards the both par...
3 Leicht B. G., McAllister B.F. 2014. Foundations of Biology 1411, 2nd edition. Southlake, TX: Fountainhead Press. Pp 137, 163-168, 177-180,
The book Genome by Matt Ridley tells the story of the relationship between genome and life by examining the twenty three chromosomes of the human DNA. Each chromosome literally and metaphorically becomes a chapter in the literal and metaphorical book of DNA. In this book of DNA, Ridley examines a particular aspect of the chromosomes chapter by chapter to see how it affects life and humanity’s understanding of life, humans and genetics itself. Although each chapter dives into different aspects of DNA and gathers stories as varied as the genes’ applications, Ridley connects them with important ideas about life and humanity’s understanding of life.
Skeletal, smooth, and cardiac muscles play a vital role in the everyday processes that allow the human body to function. Without these muscles, everyday tasks and functions could not be conducted. Injury to these muscles could cause serious problems, however, these muscles have the ability to regenerate, repair, and fix multiple problems all by themselves. Repair and regeneration of a muscle are two similar, yet different things. Repair restores muscle continuity so that it can continue to function in the same way as before injury, but does not completely restore the pre-injury structure like regeneration (Huijbregts, 2001). Muscle repair and regeneration take place after an injury, after surgery, after atrophy, and even after working out.
In the 19th century, Mendel’s relatively new science of inheritance and hereditary has increasingly developed into what we commonly understand today as genetics. Peter J. Bowler describes this field as becoming “a very active area of scientific research”.
Epigenetics ~ Is the term coined to explain a variety of “bizarre” phenotypic phenomena in different organisms that can’t be elucidated by Mendelian Genetics. It is like a bridge between geno and phenotypes ~ giving explanation to how cells carrying identical DNA differentiate into different cell types and how this differentiated state remains stable;
Precise chromosomal DNA replication during S phase of the cell cycle is a crucial factor in the proper maintenance of the genome from generation to generation. The current “once-per-cell-cycle” model of eukaryotic chromosome duplication describes a highly coordinated process by which temporally regulated replicon clusters are sequentially activated and subsequently united to form two semi-conserved copies of the genome. Replicon clusters, or replication domains, are comprised of individual replication units that are synchronously activated at predetermined points during S phase. Bi-directional replication within each replicon is initiated at periodic AT-rich origins along each chromosome. Origins are not characterized by any specific nucleotide sequence, but rather the spatial arrangement of origin replication complexes (ORCs). Given the duration of the S phase and replication fork rate, adjacent origins must be appropriately spaced to ensure the complete replication of each replicon. Chromatin arrangement by the nuclear matrix may be the underpinning factor responsible for ORC positioning. The six subunit ORC binds to origins of replication in an ATP-dependent manner during late telophase and early G1. In yeast, each replication domain simply contains a single ORC binding site. However, more complex origins are characterized by an initiation zone where DNA synthesis may begin at numerous locations. A single round of DNA synthesis at each activated origin is achieved by “lic...
Every cell in every living organism contains DNA, or deoxyribonucleic acid. DNA is wound up around proteins to form chromosomes, and along these chromosomes are sections which code for different traits in the organism, known as genes. Thus the program of genetics is written in the language of DNA (Steitz undated). Chromosomes are comprised of thousands of genes, each having specific sequences of nucleotides which code for specific traits in the organism or functions within each cell. These features could include eye or hair colour of a human, or a specific protein or enzyme which can produce an organism’s inherited traits (Steitz undated).
Thomas Hunt Morgan, Calvin Bridges and their colleagues have been recognized for their work in discovering recombination frequencies, the chance of a crossover occurring between sister chromatids, and identifying and mapping the location of genes for each chromosome. Their work began in the
A Karyotype is when you cut out individual chromosomes from a picture and rearrange them. There are matching pairs of chromosomes these are called homologous pairs. Each pair is given a number. One of each pair came from the mother and one of each pair came from the father. The pairs can be distinguished as each pair has a distinctive banding pattern when stained. There are two sex chromosomes and the rest are called autosomes. In most karyotype the sex cells are kept to one side so that the sex can be seen easily. In females they have two X chromosomes and in the males they have an X and a Y chromosome. The Y chromosome has a portion missing and is therefore smaller then the X chromosome.
The. San Francisco: Benjamin Cummings, 2002. Print. The. The "Epigenetics" of the "Epigenetic PBS. PBS, 09 Jan. 2000.
Ntanasis-Stathopoulos, J, Tzanninis, JG, Philippou, A, Koutsilieris, M. Epigenetic Regulation on Gene Expression Induced by Physical Exercise. Musculoskeletal Neuronal Interaction, 2013 Jun.
Prokaryotic cells do not have a nucleus. The chromosomes which are found in prokaryotes are usually spread in the cytoplasm. In eukaryotic cells the chromosomes remain together inside the nucleus and there is a clear nuclear membrane that is surrounding the nucleus.
In metaphase I, bivalents, each composed of two chromosomes, align at the metaphase plate. The orientation is random, with either parental homologue on a side. This means that there is a 50-50 chance for the daughter cells to get either the mother's or father's homologue for each chromosome.