Biol 207 - Genetics 2

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Biol 207 - Genetics 2
2013-03-15 04:46:00
Introductory Genetics

Dr. Deyholos Biol 207 Genetics. second midterm. U of A
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  1. p
    the frequency of the dominant allele within a population
  2. q
    frequency of recessive allele within a population
  3. Hardy-Weinberg formula
    • p+ 2pq + q2 = 1
    • both the genotype frequencies and allele frequencies in a population are unchanged following matings within a population.
  4. Hardy-Weinberg Conditions
    • Random mating: individuals mate together with equal frequencies
    • No natural selection: genotypes have equal fitness
    • No migration: no leaving or entering of the population
    • No mutation: allele frequencies do not change due to mutation
    • Large population: need a large population to reduce random sampling effects (genetic drift)
  5. Assortative mating
    when genotypes preferentially mate together. type of non-random mating
  6. Dihybrids
    carry two alleles at each of two loci. heterozygous for alleles of two genes.
  7. 9:3:3:1
    • typical phenotypic dihybrid cross ratio results. ratio's can be obtained by using the product rule for each of the monohybrid cross results.
    • assumes loci assort independently
    • assumes complete dominance of alleles
    • assumes phenotypes can be interpreted easily with no interactions between the genes
  8. Law of Independant assortment
    two loci assort independently of each other during gamete formation
  9. Linkage
    alleles of loci located close together on the same chromosome tend to be inherited together.
  10. Epistasis
    The interaction of genes that are not alleles, in particular the suppression of the effect of one such gene by another. The phenotype differs from what would be expected if the loci were expressed independently and indicates the genes interact in the same biological pathways
  11. Recessive Epistasis
    • when a singly homozygous recessive genotype (aaB_ or AAB_) has the same phenotype as the double homozygous recessive (aabb).
    • 9:3:4 ratio
  12. Dominant Epistasis
    when a dominant allele at one locus masks the second locus' phenotype

    12:3:1 ratio

    ex: A allele is epistatic to both B and bb combinations so whenever there is "A" that will produce only 1 allele no matter what the second allele produces.
  13. Duplicate Gene Action
    aka redundancy.

    When two loci have redundant functions in the same biological pathway so that they both produce identical phenotypes. only the double recessive phenotype shows a different phenotype.

    15:1 ratio
  14. Complementary Gene Action
    when the genes work together (complementary) to produce a final product and without each other a loss of function occurs

    9:7 ratio
  15. recombination
    process resulting in gametes with combinations of alleles that were not present in previous generations gametes
  16. Interchromosmal recombination
    Independant assortment of alleles whose loci are on different chromosomes
  17. Intrachromosmal recombination
    recombination occurring through crossovers between loci on the same chromosome.
  18. recombinant genotype
    products of meiosis that resulted in recombination of gametes
  19. parental genotype
    • products of meiosis which have original genotypic combinations
    • aka non-recombinant
  20. unlinked
    no physical connections between loci. loci are on different chromosomes, will segregate independently.

    50% chance of recombinant or parental gametes with unlinked loci.
  21. Recombination frequency
    • RF
    • number of recombinant gametes divided by the total number of gametes.

    • Maximum 50% (unlinked loci)
    • Min 0% (complete linkage)
  22. complete linkage
    • aka absolute linkage
    • loci are so close together on the same chromosome that parental combinations of alleles always segregate together. no crossovers ever occur.

    0% RF
  23. incomplete linkage
    aka partial linkage

    when two loci are located on the same chromosome but the loci are far enough them occur sometimes but not always during meiosis
  24. synapsis
    alignment/connection of homologous chromosomes during prophase 1 of meiosis 1
  25. crossovers
    double strand breakage of a pair of non-sister chromatids which then connect to the opposite chromatid and exchange sections of DNA. occurs during prophase 1 of meiosis via synapsis.
  26. coupling configuration
    • cis-configuration
    • two dominant alleles are together on a chromosome and the two recessive alleles are together on another chromosome
  27. repulsion configuration

    recessive and dominant alleles are together on one chromosome
  28. map units (mu) or centiMorgans (cM)
    units of gentic distance. proportional to the RF.

    shorter distances are more accurate (RF<30%) and maxes out at 50%
  29. Genetic Map
    by combining the results of multiple genetic distances the loci of a chromosome can be obtained therefore giving a rough idea of positions of loci relative to other loci.
  30. double-crossovers
    when two crossovers occur between the loci which creates gametes with the same genotypes as a non-recombination event (50% RF)
  31. Three -point cross
    pure breeding lines with different genotypes are crossed producing a triple heterozygous individual which is testcrossed. Allows the order and distance between three linked genes to be determined.
  32. Molecular biology
    techniques involving the study of DNA and macromolecules that have been isolated from an organism
  33. Molecular Genetics
    combination of techniques to isolate and analyze DNA or RNA transcribed from a particular gene
  34. detergents
    dissolve membranes and denature proteins
  35. Chelating agent
    ex. EDTA

    protects DNA by sequestering Mg2+ ions, which otherwise would act as a co-factor for nucleases
  36. nucleases
    enzymes which digest DNA
  37. supernatant
    contains DNA and smaller metabolites
  38. Pellet
    small clump of DNA that forms after centrifugation. Can be used in other reactions after addition of water.
  39. PCR
    Polymerase Chain Reaction: method of DNA replication and amplication

    • 1) add DNA polymerase + nucleotides + DNA template + DNA primers + pH buffer + ions (Mg2+)
    • 2) Thermacycling: series of precise temperatures. first 95o
    • 3) Annealing: cooling (45-65oC) that allows forming of double stranded helices and annealing of primers to templates
    • 4) Extension: 72oC temp allows for DNA polymerase to be most active and synthesize  the new DNA strand starting from the primer. 
    • repeat 30 times.
  40. Taq DNA pol
    from Thermus acquaticus it is a thermostable DNA polymerase which allows it to survive the increased temperatures during PCR.
  41. restriction endonucleases
    • enzymes that recognize a specific DNA sequence and cuts the DNA helix at this location
    • aka restriction enzymes
  42. sticky-ends
    ends of DNA that have an overhanging single stranded section. caused by certain restriction enzymes
  43. Blunt-ends
    ends of DNA that have been cut without leaving any overhanging single strands
  44. DNA ligation
    when DNA strands are covalently joined, end to end. accomplished by enzyme called DNA ligase
  45. Compatible ends
    complementary overhanging sticky ends and blunt ends are compatible but non complementary sticky ends are not and won't be ligased together
  46. plasmids
    small circular double stranded molecules that replicate independently.
  47. transformed
    describes the process of inserting a DNA plasmid into a bacteria
  48. competent
    cells that have been prepared so that they can uptake DNA. Done through exposue to CaCl2 or electical fields (electroporation)
  49. selectable marker
    gene present on a plasmid that is transformed into a bacteria in order to differentiate between bacteria that have the uptaken plasmid and those that don't
  50. vectors
    A bacteriophage, plasmid, or other agent that transfers genetic material from one cell to another
  51. gel electrophoresis
    used to detect and analyse DNA.

    done by DNA being put at one end of a gel (made of agarose) and then DNA is pushed by an electrical current (towards positive electrode).

    shorter sections of DNA will travel further so molecules are separated by length of DNA forming bands.
  52. ethidium bromide
    a fluorescent dye that is used to make DNA bands visible in gel electrophoresis
  53. Southern Blot
    • 1)DNA is digested with restriction enzymes and put through gel electrophoresis
    • 2) nylon or similar material is put under the gel and through "blotting" the DNA is transferred to the nylon membrane and covalently attached through UV light
    • 3) hybridization solution containing a probe DNA (labled with flourescent or radioactive molecules) that is complementary to the target molecule is used to bath the membrane
    • 4) washing of the membrane to remove extra probe
    • 5) exposure to X-ray shows the probe location and therefore the fragment size

    Temperature and washing solutions change the "stringency" (specificity) of the probe. Higher temp = more exact
  54. Northern blot
    same procedure as the Southern blot except with RNA and without restriction enzymes in order to observe the full size of an RNA transcript
  55. Western Blot
    same procedure as the southern blot except with proteins and use of an acrylamide gel. the probe is an antibody that binds to an antigenic site on the target protein. These probes are observed by adding other antibodies with flourescent  or colour marker systems
  56. non-disjunction
    failure of chromosomes to segregate properly during any Anaphase
  57. euploid
    cells that have the proper number of chromosomes
  58. aneuploid
    cells that have one too many or one too few chromosomes. both cells will likely die.
  59. unbalanced genotypes
    aneuploid cells that have two many copies or too many copies of hundreds of genes. (over or underproduction)
  60. First division nondisjunction
    a nondisjunction during Anaphase 1 of meiosis. results in unbalanced gametes, which will still fertilize but the embryo won't likely survive
  61. Second division nondisjunction
    a nondisjunction during Anaphase 2 of meiosis. results in unbalanced gametes which will still fertilize but the embryo won't likely survive.
  62. NHEJ
    nonhomologous end joinging system: repair system to fix double strand breaks through proteins binding to ends of DNA and reattaching covalent bonds.
  63. chromosome rearrangement
    when the NHEJ system proteins join the ends of improper strand brekas. Can occur when there are multiple double strand breaks.
  64. changes in chromosome structure
    • 1) incorrect repair of double strand DNA breaks during interphase
    • 2) incorrect crossovers during meiosis
  65. Deletions
    both breaks on one chromosome and a section is removed
  66. Inversions
    Both breaks on one chromosome and a section is flipped in the chromosme
  67. paracentric inversion
    inversion that does NOT include the centromere
  68. pericentric inversion
    inversion that DOES include the centromere
  69. Tandem duplications
    one break on each homologous chromosomes or sister chromatids where a section is stolen from one chromosome and put onto another
  70. Translocations
    breaks occurring on unrelated chromosome where chromosomes exchange sections.
  71. reciprocal translocation
    when both chromosomes contribute and swap sections.
  72. Robertsonian translocations
    • when all the genes of a translocation end up on one chromosome and the other becomes tiny and is lost.
    • Rare