PGX lecture 2

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PGX lecture 2
2011-01-31 01:41:01
im too cool

munson .. Single gene inheritance and independent assortment
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  1. genome
    • the entire complement of genetic material in a chromosome set.
    • an organism’s unique and complete set of genetic
    • information (DNA)
  2. chromosome
    a linear end-to -end arrangement of genes and other DNA, sometimes with associated protein and RNA
  3. gene
    the fundamental physical and functional unit of heredity, which carries information from one generation to the next; a segment of DNA composed of a transcribed region and a regulatory sequence that makes transcription possible
  4. DNA
    • deoxyribonucleic acid
    • a chain of linked nucleotides (having deoxyribose as their sugars). Two such chains in double helical form are the fundamental substance of which genes are composed.
  5. haploid
    a cell having one chromosome set or an organism composed of such cells
  6. diploid
    a cell having two chromosome sets or an individual organism having two chromosome sets in each of its cells
  7. nucleosome
    the basic unit of eukaryotic chromosome structure; a ball of eight histone molecules that is wrapped by two coils of DNA
  8. chromatin
    • the substance of chromosomes; now known to include DNA and chromosomal proteins.
    • condense chromatin = chromosome
  9. heterochromatin
    • densely staining condensed chromosomal regions, believed to be for the most part genetically inert.
    • dense packing, dark staining, generally inactive
  10. euchromatin
    • a less-condensed chromosomal region, thought to contain most of the normally functioning genes.
    • looser packing, lighter staining, more active (transcriptionally)
  11. centromere
    • a specialized region of DNA on each eukaryotic chromosome that acts as a site for the binding of kinetochore proteins.
    • dense chromatin near “center” ofchromosome
  12. telomere
    • the tip, or end, of a chromosome.
    • the “tips” of a chromosome, also somewhat dense – think of it as the knots that keep a chromosome from unraveling
  13. autosome
    • any chromosome that is not a sex chromosome.
    • autosomal chromosome --> 22 pairs --> does not differ male to female
  14. sex chromosome
    • a chromosome whose presence or absence is correlated with the sex of the bearer; a chromosome that plays a role in sex determination.
    • sex linked --> the XX or XY pair
  15. intron
    • aka intervening sequence
    • a segment of largely unknown function within a gene. This segment is initially transcribed, but the transcript not found in the functional mRNA.
    • The non-expressed (transcribed but not translated) portion of the coding sequence of a gene.
  16. exon
    • any nonintron section of the coding sequence of a gene; together, the exons correspond to the mRNA that is translated into protein.
    • the expressed (transcribed and translated) portion of the coding sequence
  17. intergenic space
    The space between genes. Not transcribed or translated but may serve a regulatory function.
  18. allele
    • one of the different forms of a gene that can exist at a single locus.
    • a form or variant of a gene. Usually comes in “wild type” and “mutant(s)”. Wild type is usually defined as the most common form (and is often dominant to any variants/mutants). In a population there can be multiple alleles.
  19. homozygous
    refers to the state of carrying a pair of identical alleles at one locus
  20. heterozygous
    refers to the state of carrying a pair of different alleles at one locus
  21. phenotype
    • (1) the form taken by some character (or group of characters) in a specific individual. (2) the detectable outward manifestations of a specific genotype.
    • Observable expression of genotype. Morphological, biochemical, physiological or behavioral trait. Changes throughout life; influenced by environment & development.
    • Phenotype = genotype x environment x development
  22. genotype
    • the specific allelic composition of a cell - either of the entire cell or, more commonly, of a certain gene or a set of genes.
    • Gene(s) associated with a given trait. Essentially a fixed character of an organism (except for rare mutations).
  23. mitosis
    • a type of nuclear division (occurring at cell division) that produces two daughter nuclei identical with the parent nucleus.
    • “conservative” division mother and daughter cells identical
  24. meiosis
    • two successive nuclear divisions (with corresponding cell divisions) that produce gametes (in animals) or sexual spores (in plants and fungi) that have one-half of the genetic material of the original cell.
    • “reductive” division mother and daughter cells different
  25. tetrad
    • (1) four homologous chromatids in a bundle in the first meiotic prophase and metaphase. (2) the four haploid product cells from a single meiosis.
    • Four homologous chromatids in a bundle in the first meiotic prophase and metaphase
  26. dyad
    a pair of sister chromatids joined at the centromere, as in the first division of meiosis.
  27. (sister) chromatid
    • one of the two side-by-side replicas produced by chromosome division.
    • together in the "x" formation
  28. homolog
    • a member of a pair of homologous chromosome.
    • The two members of a chromosome pair in a cell
  29. hemizygous
    a gene present in only one copy in a diploid organism - for example, an X-linked gene in a male mammal.
  30. equal segregation
    • equal numbers of progeny genotypes attributable to the separation of two alleles of one gene at meiosis.
    • Mendel's first law:
    • the two members of a gene pair segregate from each other in meiosis; each gamete has an equal probability of obtaining either member of the gene pair
  31. independent assortment
    • Mendel's second law:
    • unlinked or distantly linked segregating gene paris assort independently at meiosis.
    • gene pairs on different chromosome pairs assort independently at meiosis
  32. recombination
    • (1) in general, any process in a diploid or partly diploid cell that generates new gene or chromosomal combinations not previously found in that cell or in its progenitors. (2) at meiosis, the process that generates a haploid product of meiosis whose genotype is different from either of the two haploid genotypes that constituted the meiotic diploid.
    • Meiosis generates recombinants, which are haploid meiotic products with new combinations of the alleles/chromosomes than carried by the haploid genotypes that united to form the meiocyte.
  33. polygenes/quantitative trait loci (QTL)
    • aka multiple factor hypothesis
    • a hypothesis that explains quantitative variation by assuming the interaction of a large number of genes (polygenes), each with a small additive effect on the character.
    • QTL: a gene affecting the phenotypic variation in continuous varying traits such as heigh and weight, among others