genetics bio 10c

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  1. allele
    alternate form of the same gene
  2. wild-type allele
    allele that occurs most frequently in a population
  3. what is the source of alleles?
  4. consequences of loss-of-function mutation...
    • mutation may change overall enzyme shape
    • thus, affecting affinity for substrate!
  5. null allele
    mutation causes a complete loss-of-function
  6. gain-of-function mutation
    • enhance allele function
    • usually increase quantity of gene by affecting the regulation of transcription
  7. neutral mutation
    show no change in function
  8. incomplete, or partial, dominance
    • a cross between contrasting traits that produces an intermediate phenotype
    • [phenotypic ratio = genotypic ratio]
    • Ex: red x white snapdragons... F1 all pink, pink x pink -- 1red : 2pink : 1white
  9. Tay-Sachs disease
    homozygous recessives die from fatal lipid-storage disorder, when hexosaminidase activity is absent
  10. the joint expression of both alleles in a heterozygote is called ________.
    • codominance
    • distinct expression of the gene products of both alleles
    • Ex: MN blood group in humans
  11. three or more alleles of a gene
    • multiple alleles
    • can only be studied in populations, not individuals
    • Ex: ABO blood group
  12. Human ABO blood groups...
    derived by...
    • A and B antigens are present on the surface of blood cells
    • derived by a precursor molecule called H substance

    recall: Iand IB are dominant to the IO but codominant to each other
  13. very rare phenotype from incomplete formation of H substance called:
    • Bombay phenotype
    • cause: terminal sugar cannot be added thus neither A nor B antigen can be added to the cell surface
    • IA + IB = IO
  14. genes that are absolutely required for survival
    essential genes
  15. dominant lethal allele
    • the presence of just one copy of the allele results in the death of the individual 
    • Ex: Huntington disease
  16. recessive lethal alleles result in...
    homozygous recessive individuals that don't survive
  17. Huntington disease due to _______.
    Age of onset:
    Child's chance of inheritance :
    • autosomal dominant allele
    • about 40 yrs old
    • 50% chance of children inheriting
  18. gene interaction
    • several genes influence a particular characteristic 
    • -- the cellular function of numerous gene products contributes to the development of a common phenotype
  19. developmental concept whereby each step of development increases the complexity of the sensory organ and is under the control and influence of one or more genes
  20. epistasis...
    2 types...
    • the expression of gene or gene pairs masks or modifies the expression of another gene or gene pair
    • antagonistic (masking)-- homozygous recessive allele prevents/overrides expression of alleles at another locus (hypostatic to 1st locus)
    • complementary -- a dominant allele at 1st locus influences allele of 2nd gene locus
  21. example of recessive epistasis
    a mouse bb genotype masks or suppresses the expression of the A gene, mouse is albino
  22. Gene interactions modify dihybrid F2 ratio (9:3:3:1). Epistasis combines 1 or more of the 4 phenotypes in various ways ASSUMING THE FOLLOWING 5 FACTORS:
    • 1. inheritance is discontinuous (distinct phenotypes)
    • 2. genes are not linked (assort independently)
    • 3. complete dominance exists (A_ or B_)
    • 4. all P1 crosses homozygotes/ F1 heterozygotes 
    • 5. F2 is the focus of analysis
  23. hemizygous
    males have a single copy of genes encoded by the X chromosome
  24. lethal X-linked recessive disorders are observed only in _________
  25. sex-limited inheritance vs sex-influenced inheritance
    • sex-limited: expression of phenotype absolutely limited to one sex (milk or feather plumage)
    • sex-influenced: the sex of an individual influences the expression of a phenotype; not limited to one sex or another (baldness)
  26. penetrance vs expressivity
    • penetrance - the percentage of a population  that express a mutant genotype
    • expressivity - the range of expression of the mutant phenotype
  27. genetic anticipation
    • when a genetic disease gets worse and arrives earlier in life with successive generations 
    • [Huntington]
  28. criteria for "model organisms" for genetic study
    • easy to grow
    • short life cycle
    • produce many offspring
    • genetic analysis straightforward
  29. mustard plant (L.)
    Arabidopsis thaliana
  30. spermatogenesis
    production of a male gamete
  31. oogenesis
    production of a female gamete
Card Set:
genetics bio 10c
2015-09-23 15:36:25
genetics bio 10c
genetics bio 10c
genetics bio 10c
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