genetics 3

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genetics 3
2013-03-15 17:19:01

exam 3
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  1. population
    group of individuals with a common set of genes that lives in the same geographic area and actively or potentially interbreed
  2. gene pool
    all the alleles in a population
  3. Hardy-Weinburg model
    describes the relationship between allele frequencies and genotype frequency
  4. Hardy-Weinberg assumes:
    • that in an ideal population:
    • -there is no selection
    • -no new alleles arise from mutation
    • -there is no migration into or out of the population
    • -the population is infinitely large
    • -random mating occurs
  5. natural selection
    principle force that shifts allele frequencies within large populations

    individuals do not have an equal rate of survival and reproductive success, allele frequencies may change from one generation to the next
  6. fitness
    an individual organism's genetic contribution to future generations
  7. what does selection work to do in natural populations
    increase the frequency of the allele to which selective pressure is applied

    no such increase is observed in populations not subjected to the selection
  8. bacteria and viral chromosomes are usually?
    a single nucleic acid molecule

    largely devoid of associated proteins

    much smaller than eukaryotic chromosomes

    chromo viruses single/double stranded RNA/DNA

    chromo bacteria double-strained DNA, compacted into nucleoid
  9. supercoiling
    compacts DNA

    mostly closed circular DNA mlcs. in bacteria are slightly underwound and supercoiled
  10. topoisomerases
    cut one or both DNA strands and wind or unwind the helix before resealing the ends
  11. polytene chromosomes
    • -have distinctive banding patterns
    • -represent paired homologs
    • -are compes of many DNA strands (undergoes many replications w/out strand separation or cytoplasmic division)
  12. puff regions
    areas where DNA has uncoiled and are visible with high level of magnification, found in polytene chromosomes
  13. Lampbrush chromosomes
    large and have extensive DNA looping

    found in oocytes during meiosis
  14. Chromatin
    complex nucleoprotein structure in eukaryotic chromosomes

    bound in nucleosomes with histones ( 4 kinds H2A, H2B, H3 AND H4)
  15. histone tails
    needed for histone modifications such as acetylation, methylation, and phosphorylation
  16. euchromatin
    eukaryotic domain, uncoiled and active
  17. heterochromatin
    eukaryotic domain, condensed and inactive
  18. centromeres
    primary constrictions along eukaryotic chromosomes

    mediate chromosomal migration during mitosis and meiosis
  19. telomeric DNA sequence
    • short tandem repeats
    • -protect the ends of chromo. from being degraded or becoming attached to other chromo.
    • -provide a way to replicate DNA at the end of chromosomes
  20. telomerase
    directs synthesis of the telomere repeat sequence to fill the gap

    -ribonucleoprotein + RNA, serves template for synthesis of DNA complement
  21. known variations in chromosomes
    - changes in the total number of chromosomes

    -rearrangements of the genetic material either w/in or among chromosomes
  22. aneuploidy
    variations in chromosome number

    organism gains or loses one or more chromosomes and has other than an exact multiple of the haploid set

    does not lose a whole set
  23. nondisjunction
    chromosomes or chromatides fail to disjoin and move to opposite poles during meiosis 1 or 2

    cause chromosomal variation
  24. monosomy
    loss of one chromosome

    produce 2n-1 complement

    occurs in x chromosome, any other autosomes is usually not tolerated in humans and other animals
  25. turner syndrome
    monosomy for x chromosome
  26. trisomy
    three copies of one chromosome are present, pairing configurations are usually irregular


    often found in spontaneously aborted fetuses, but monomies are not
  27. trivalent
    3 copies of a chromosome are synapsed

    1 bivalent + 1 univalent (unpaired chromo.) may be present
  28. Down Syndrome
    trisomy of chromosome 21

    increase incidence w/ increasing maternal age
  29. Patau syndrome
    trisomy 13

    extra chromosome 13 disrupts normal course development, causing heart and kidney defects
  30. Edward syndrome
    trisomy 18
  31. polyploids
    more than 2 sets of chromosomes are present from same species (autoployploid) or different species (alloployploidy)

    • named by number of sets found
    • 3-triploid
    • 4-tetraploid
    • 5-pentaploid
  32. euplodity
    complete sets of chromosomes are present
  33. allotetraploid
    forms from hybridization of 2 closely related species
  34. endopolyploidy
    condition which only certain cells in an otherwise diploid organism are polypoid

    replication and segregation of chromosomes occur w/out nuclear division

    entire organism is normal only some cells mutate
  35. known chromosome mutations/aberrations variations:
    change in total number of chromosomes

    rearrangements of the genetic material either w/in or among chromosomes
  36. rearrangements of chromosome segments include:
    • -deletions
    • -duplications
    • -inversions
    • -nonreciprocal translocations
    • -reciprocal translocations
    • -chromosomal breakage
  37. deletion/deficiency
    chromosome breaks in one or more places and a portion of it is lost
  38. terminal deletion
    deletion of chromosome near one end
  39. intercalary deletion
    deletion of chromosome from interior of chromosome
  40. duplication
    result of unequal crossing over during meiosis or through a replication error prior to meiosis

    may play role in evolution
  41. gene redundancy
    multiple copies of ribosomal RNA genes
  42. inversion
    rearrangement of the linear gene sequence rather than the loss of genetic info.


    requires 2 breaks in chromo. and subsequent reinsertion of inverted segment

    may arise from chromo. looping
  43. paracentric inversion
    does not change the relative lengths of the two arms of a chromo.
  44. pericentric inversion
    includes the centromer, does change the length of two arms of chromo.
  45. translocation
    movement of a chromosomal segment to a new location in the genome

    alters location of chromosomal segments in genome
  46. reciprocal translocation
    involves exchange of segments between 2 nonhomologous chromo.

    has unusual synapsis configuration during meiosis

  47. Robertsonian translocation/centric fusion
    breaks at the extreme ends of the short arms of two nonhomologous acrocentric chromo. (chromosome broke in half)

    ex. familial down syndrome
  48. familial down syndrome
    down sydrome occasionally runs in families

    translocation of chromosome 21
  49. fragile sites
    more susceptible to chromosome breakage when cells are cultured in the absence of certain chem. such as folic acid
  50. fragile s syndrome (martin-bell syndrome)
    most common form of inherited mental retardation
  51. repetitive DNA
    sequences are repeated many times w/in eukaryotic chromo.

    many different categories of repetitive DNA

    used as DNA markers to identify individuals
  52. pseudogenes
    single-copy noncoding regions

    usually not transcribed
  53. DNA marker
    specific unique location in the genome

    different ppl. have different amount of copies of dna
  54. polymorphic
    more that one allele
  55. carrier testing
    DNA testing done to determine if they carry a recessive mutation
  56. presymptomatic testing
    DNA testing to determine if they have the disease causing mutation

    family history of dominate late onset disease
  57. neonatal screening
    DNA testing on newborn infant , soon develop genetic disease
  58. prenatal testing
    DNA testing of fetus, tested for chromosomal mutations or gene mutations
  59. preimplantation diagnosis
    DNA testing of embryo produced by in vitro fertilization , test for genetic mutations when parents history put them at high risk

    usually multiple embryos
  60. cyclin-dependent kinases (Cdks)
    inactive unless bound to cyclins

    cyclin helps direct Cdks to target proteins

    different cyclin binds to different Cdks

    levels peak of cyclin and m-cdk during mitosis
  61. apoptosis
    process of programmed cell death
  62. causes of apoptosis
    • -embryonic morphogenesis
    • -killing by immune effector cells
    • -wiring of the developing nervous system
    • -regulation of cell viability by hormones and growth factors (cells die if fail to receive signals from other cells)
    • -misregulation of apoptosis contributes to cancer, alzheimer's disease, AIDS, ischemia
  63. necrosis
    process of traumatic cell death that results from acute cellular injury
  64. clonal
    originate from a common ancestral cell that accumulated numerous specific mutations

  65. genomic instability
    cancer cells manifests itself in gross defects such as translocations, aneuploidy, chromosomal deletions
  66. epigenetic
    changes such as DNA metylation and histone acetylation modify gene expression, potentially leading to tumor progression
  67. proto-oncogenes
    genes whose products promote cell growth and division
  68. proto-oncogens encode:
    • -transcription factors that stimulate expression of other genes
    • -signal transduction mlcs. that stimulate cell division
    • -cell-cylce regulators that move through the cell cycle
  69. oncogenes
    mutated version of proto-oncogens
  70. tumor suppressor genes
    normally regulate cell cycle checkpoints and initiate the process of apoptosis

    when mutated cells are unable to respond normally to cell cycle checkpoints or are unable to undergo apoptosis if DNA damage is extensive
  71. p53 tumor suppressor gene
    encodes a nuclear protein that acts as a transcription factor that represses or stimulates transcription of more than 50 different genes

    mutation 50% cancer
  72. loss or mutation of both alleles of the RB1 tumor suppressor gene contributes to many different cancers due to unregulated progression in cell cycle
  73. familial retinoblastoma
    mutate RB1 inherited
  74. sporadic retinoblastoma
    requires two independent mutational events of RB1 w/in same cell
  75. metastasize
    cancer cells digest components of extracellular matrix and basal lamina that normally inhibit the migration of cells

    -must happen for cancer cells to migrate, cancer cell from lung to liver
  76. inherited cancer
    not able to trigger cancer themselves, does create a higher risk

    another mutation in a gene usually needed to fully express cancer
  77. retroviruses
    animal viruses that cause cancer
  78. acute transforming retroviruses
    viruses that transform cells into cancer cells

    most viruses in animals
  79. carcinogenic
    substance that causes mutations to occur in proto-oncogenes or tumor suppressor genes

    -chemicals, radiation, some viruses, chronic infection
  80. gastrulation
    phase in early embryonic development to form three germ layers: ectoderm, mesoderm, endoderm
  81. ectoderm
    -epidermis, neural plate, neural crest
  82. mesoderm
    notochord, muscle, kidney, blood, heart
  83. endoderm
    -liver, stomach, pancreas, pharynx
  84. maternal-effect genes
    developing egg, and most distributed or conc. in specific regions of the cell
  85. zygotic genes
    expressed during embryo development, often regulated by products of maternal-effect genes
  86. gap gene mutations
    produce large gaps in the embryo's segmentation pattern
  87. homeotic mutants
    cause transformation of body segents

    not found in humans=lethal, usually causes spontaneous abortion