Bio10 - Genetics

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mse263
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292612
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Bio10 - Genetics
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2015-01-07 20:26:18
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Biology
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Video Set 10
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  1. 10.1 Genetics Vocabulary
  2. Allele
    one variation of a gene
  3. Locus
    location on a chromosome
  4. Homologous Chromosomes
    chromosomes that have the same sets of genes; may not have all the same alleles
  5. Codominance
    • when each gene codes for an end product expressed equally
    • eg. blood type (A, B, AB, O); if a person is AB, both A & B antigens get expressed equally on the surface of cells
  6. Incomplete Dominance
    • when the heterozygous genotype manifests as a blending of the dominant & recessive alleles
    • eg. snapdragon plants: RR = red, rr = white, Rr genotype = pink*
  7. Leakage
    when a gene for a particular trait is knocked out however there is still a slight phenotype expressed
  8. Penetrance
    • the percent that a genotype is expressed as a corresponding phenotype
    • eg. if only 95/100 ‘RR’ snapdragons are actually red → the RR gene has a 95% penetrance
    • (not all organisms with the same genotype have the exact same phenotype)
  9. Expressivity
    • the degree to which a genotype is expressed effects an organisms phenotype
    • eg. 3 brothers have a gene that produces excess growth hormone; one is 7’, one is 6’8”, & the 3rd is 6’5”
  10. Polygenism
    when multiple genes influence a single phenotypic characteristic/trait
  11. Pleiotropism
    when a SINGLE gene affects multiple phenotypic traits
  12. Epistasis
    when the expression of one gene is dependent upon another gene also being expressed
  13. Gene Pool
    all the different alleles present in a population
  14. 10.2 Meiosis
  15. Interphase
    • where you are if you’re not in mitosis
    • chromosome condensation takes place
  16. G1 Phase (& ~G0)
    growth happens: amount of cytoplasm expands, organelle growth occurs, etc.
  17. S Phase
    when Synthesis of DNA occurs, so DNA replication
  18. Prophase
    • nuclear envelope begins to dissolve
    • chromosome condensation continues
    • polarization: centrosomes (microtubule organizing centers) start moving toward opposite ends of the cell
  19. Metaphase
    • chromosomes line up along the metaphase plate
    • spindle fibers attach centromeres to kinetochores
    • Kinetochores are protein structure on chromatids where the spindle fibers attach during cell division to pull sister chromatids apart
  20. Anaphase
    • spindle fibers retract toward centrosomes on opposite poles of the cell & pull sister chromatids apart
    • (sister chromatids are identical copies of a chromosome)
    • Cytokinesis (cleavage furrow) may begin
  21. Mitosis v. Meiosis
    • want 4 resulting cells from meiosis as opposed to 2 from mitosis
    • those 4 cells should be haploid as opposed to 2 diploid
    • DNA replication takes place only ONCE prior to both events
  22. Prophase I of Meiosis
    • *only place where DNA CROSSING OVER occurs
    • tetrads (2 sets of homologous chromosomes, each made up of 2 identical sister chromatids) line up & cross over, an example of recombination
    • PI is the longest phase in meiosis
  23. Tetrad
    • when homologous chromosomes line up alongside each other
    • homologous chromosomes are not identical, they’re homologous (contain the same genes but individual alleles can be different)
    • sister chromatids are identical copies of each other
  24. What gets “pulled apart” in meiosis I v. meiosis II?
    • meiosis I: homologous chromosomes
    • meiosis II: identical sister chromatids
    • *meiosis II is analogous to mitosis, b/c during both sister CHROMATID (not homologous chromosomes) are pulled apart
  25. Nondisjunction
    • when homologous chromosomes aren’t pulled apart in meiosis I OR sister chromatids fail to be pulled apart in meiosis II
    • eg. down syndrome can be the result of nondisjunction
  26. Translocation
    recombination that occurs NON-homologously
  27. 10.3 Segregation of Genes & Sex-linked Traits
  28. Linkage
    • overall, genes on the same chromosome are more likely to be inherited together than genes on separate chromosomes
    • the farther away 2 genes on the same chromosome are from each other, the MORE likely nondisjunction is to occur & cause them to be potentially inherited separately
    • if 2 genes are close to each other on a chromosome, there is less of a ‘window’ between them for nondisjunction to occur (i.e. break them up), & they are likely to be inherited together
    • ~the closer genes are on a chromosome, the GREATER the degree of linkage between them~
    • you know genes are farther apart on a chromosome if they recombine with each other more frequently
  29. 10.4 Mutations
  30. Which is worse, an error in translation or transcription?
    TRANSCRIPTION errors are worse
  31. Point Mutation
    • when one DNA bases (nucleotide) is traded for another (correct is replaced with an incorrect one)
    • a single DNA base exchange
    • eg. a point mutation causes Sickle Cell Anemia
  32. Frameshift Mutation
    • insertion or deletion of a nucleotide base
    • codon reading frames get shifted so they’re no longer in the correct set of 3 orientation
    • if 3 codons in a row get inserted or deleted the reading frame doesn’t change but the protein might gain or lose an amino acid
  33. Missense Mutation
    a change in one amino acid of a protein
  34. Nonsense Mutation
    a protein’s amino acid is converted into a STOP codon
  35. Inborn Errors of Metabolism
    • a mutation typically somewhere in a key metabolic enzyme
    • results in a person either missing or having a less than functional copy of that enzyme
  36. Mutagen
    • something that causes a mutation
    • if something’s a mutagen, it has the potential to ALSO be a Carcinogen
  37. Carcinogen
    • something that causes cancer
    • most carcinogens ARE mutagens, however NOT ALL carcinogens are mutagens (eg. HPV, viruses that cause cancer, anything that speeds up the cell cycle to put a host cell at risk for missing mutations that might occur)
  38. 10.5 Population Genetics
  39. Hardy-Weinberg
    talked about populations in genetic equilibrium, which means one in which there are NO changes in allele frequencies in the gene pool
  40. Assumptions Made for ‘Equilibrium’
    • 1. Mating is random
    • 2. Population size should be LARGE
    • 3. No mutations
    • 4. No natural or artificial selection
    • 5. No migration

    • any deviation from these might change allele frequencies, which can’t happen if a population’s in equilibrium

    • assuming all of these DID happen, a population would be in H-W equilibrium
  41. Bottleneck Effect
    when a population’s size is reduced (can be caused by a random event) & as a result an allele previously seen in the population is lost from future generations
  42. p
    • FREQUENCY of the dominant allele in a population
    • allele is present in both AA & Aa people
  43. q
    • FREQUENCY of the recessive allele in a population
    • allele is present in both aa & Aa people
  44. p+q = 1
    • p & q are in decimal form & HAVE to add up to 1
    • 1*100 = 100, or 100% of the population
    • so if you multiply q or p by 100, you’ll get the percent of the population that has a given allele (A or a)
    • [p & q only work for a 2-allele system where there’s complete dominance]
  45. p2
    • the number of people in a population who have a homozygous dominant genotype
    • p2 = the # of individuals who ‘are’ AA
  46. q2
    • the number of people in a population who have a homozygous recessive genotype
    • q2 = the # of individuals who ‘are’ aa
  47. 2pq
    • the number of people in a population who have a heterozygous genotype
    • 2pq = the # of individuals who ‘are’ Aa
  48. p2 + 2pq + r2 = 1
    if having trouble squaring the decimal forms of p & q you can always convert them into fractions
  49. Probability
    • the proportion of times a specific outcome occurs in a series of events
    • eg. in a pregnancy: 1/2 girl, 1/2 boy
  50. Independent Events
    • the outcome of one event does NOT depend on outcome of other event
    • eg. a previous pregnancy does NOT affect a future one
    • each conception: 1/2 boys, 1/2 girls
  51. Multiplication Rule
    • if 2 events are INDEPENDENT of each other, the probability that both occur is the product (multiplication) of each individual event probability
    • eg. the chance of having 3 children & all of them be girls is 1/2 x 1/2 x 1/2 = 1/8
  52. Addition Rule
    • the probability of one outcome OR another is the addition of each outcome
    • eg. boy or girl = 1/2 + 1/2 = 1
    • probability of getting EITHER 2 heads in a row OR 2 tails in a row =
    • (1/2 x 1/2) + (1/2 x 1/2) = 1/4 + 1/4 = 1/2
  53. Pleiotropy
    • a mutation in a single gene that has more than one phenotypic effect on the body
    • eg. mutations in the fibrillin gene are pleiotropic - they affect the heart, skeletal system, & eye
  54. Heterogeneity
    • when multiple gene mutations causes a single phenotype
    • (contrast to pleiotropy, where a single gene mutation may cause different phenotypes)
  55. Multifactorial Inheritance
    the genetic & environmental factors that together influence a particular disease or trait
  56. Polygenic Trait
    • results from the combined influence of multiple genes
    • eg. eye color is controlled by multiple genes but can’t be changed by environmental factors
  57. Multifactorial Trait
    • results from the combined influence of multiple genes AND environmental factors
    • eg. HEIGHT
  58. Dihybrid Cross w/ Both Traits Heterozygous
    • phenotypic ratios are…
    • first do a single heterozygous cross
    • 3/4 of the population will have dominant phenotype (true for both traits)
    • 1/4 of population will have recessive phenotype (true for both traits)
    • dominant dominant: (3/4)(3/4) = 9/16
    • dominant recessive: (3/4)(1/4) = 3/16
    • recessive recessive: (1/4)(1/4) = 1/16
    • independent events so multiply! (9+3+3+1=16)
  59. 10.7 Evolution
  60. Fitness
    • ability to pass on your alleles
    • need to be alive long enough to do so & need to be able to procreate
  61. Natural Selection
    • the selection of the most advantageous traits
    • survival & the passing on of an organisms alleles
    • it is NOT random
  62. Stabilizing Selection
    when the averages are selected FOR & the extremes are selected against
  63. Divergent/Disruptive Selection
    • when the extremes are selected FOR & the averages are selected against
    • the opposite of Stabilizing Selection
  64. Directional Selection
    • when a specific allele is preferentially selected for over an opposing or different allele
    • population characteristics/alleles move in one particular ‘direction’ for a trait
  65. Artificial Selection
    when humans choose for & breed specific traits
  66. Sexual Selection
    a mode of natural selection in which some individuals out-reproduce others of a population because they are better at securing mates
  67. Species
    • an individual group of organisms that can’t breed or produce fertile offspring with organisms from a separate species
    • eg. horse & donkey can breed to produce a mule, however the mule is infertile; therefore they are separate species’
  68. Reproductive Isolation
    • different species ARE different from each other b/c they can’t produce viable offspring
    • they’re reproductively isolated from each other
    • (a collection of mechanisms, behaviors & physiological processes that prevent the members of 2 different species that cross or mate from either producing offspring or producing fertile offspring)
  69. Polymorphism
    • multiple possible phenotypes in a given population
    • eg. hair color
  70. Adaptation
    change in a heritable trait that gives better fitness (i.e. better ability to pass on alleles)
  71. Specialization
    • improves an organisms ability to accomplish something related to its habitat or environment
    • won’t necessarily make the organism more fit/better able to pass on its traits (but PROBABLY will)
  72. Genetic Drift
    • random change in allele frequencies
    • smaller populations are more succeptable
  73. Convergent Evolution
    • where two ancestrally DIFFERENT organisms develop similar phenotypes
    • they’re converging on the same phenotype from two different ‘places’ in history
  74. Divergent Evolution
    • where two ancestrally similar organisms develop different phenotypes
    • if the evolution becomes divergent enough it could lead to speciation
  75. Parallel Evolution
    when two different species’ under analagous environmental pressures develop similar adaptations to those environmental pressures independently
  76. Parasitism
    one organism is harmed while the other (parasite) benefits
  77. Commensalism
    one organism requires (benefits off?) another organism to live but there’s no benefit OR harm conferred to the host organism whatsoever
  78. Mutualism
    • both organisms symbiotically benefit from each other
    • eg. clownfish & sea anemone; bees & flowers
  79. Ontology
    stages of development
  80. Phylogeny
    tracing the evolutionary history of species to see how different species are related to one another

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