Genetics exam 2

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Genetics exam 2
2013-10-16 05:26:55
sfsu genetics

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  1. can e used to calculate the prob of any specific set of outcomes among a large number of potential events
    binomial theorem
  2. probabilities allow us to determine the likelihood that the observed deviations are due to random chance alone
  3. indicate a high prob that the observed deviations could be due to random chance alone
    low chi square values
  4. indicate a low prob that the observed deviations are due to random chance alone
    low probability
  5. if the chi square value results in a prob that is less than .05 it is considered statistically significant
  6. if p>.05 of the chi square, we fail to reject the null hypothesis
    if p<.05 of the chi square, the null hypothesis is rejected
  7. how do we predict the mode of inheritance in humans?
    experimental constraints
  8. shows a family tree with respect to a given trait
  9. pedigree analysis reveals patterns of inheritance
  10. these kind of traits can skip gen and affect both males and females equally
    autosomal recessive traits
  11. autosomal recessive traits can skip gen (appear in progeny of unaffected persons)
  12. rare recessive traits will often be expressed in
    blood relation matings (first cousins)
  13. these type of traits do not skip gen and affect both males and females
    autosomal dominant traits
  14. some children with this type of trait will be affected in every gen
    autosomal dominant
  15. affected individuals with an autosomal dominant trait are usually hetero since mutant  allele is rare
  16. those with this type of trait usually have at least one affected parent
    autosomal dominant
  17. if a trait is dominant in a pedigree what 2 things apply
    • will not skip gen
    • not be passed on to offspring unless parents have it
  18. if a trait from a pedigree is recessive what 2 things apply
    • it will skip gens (phenol not observed)
    • will exist in carriers (hetero)
  19. 5 things to do when solving a pedigree prob
    • inspect pedigree
    • form hypoth
    • deduce genotypes
    • check that geno are consistent with pheno
    • revise hypo if necessary
  20. is a source of alleles
  21. an allele that occurs most frequently in a pop
    wild type
  22. there may be more than one wild type allele in a pop
  23. wild type allele is usually dominant and is expressed as the wild type phenotype
  24. wild type alleles are used as standards for comparison for all alternative alleles of the gene/locus
  25. mutations are the source of new alleles
  26. when a mutation occurs what happens 3
    • gen info is modified
    • altered gene product is produced
    • new phenotypes arise
  27. when new phenotypes result from mutations what 2 things occur
    • elimination or change of overall func
    • change enzyme efficiency or specifics
  28. a mutation may produce no detectable change in a function, this is called
    neutral mutation
  29. a mutation may cause the red or loss of the specific wild type func, this is called
    loss of func mutation
  30. if the loss of function is completely lost, the mutation has resulted in an
    null allele
  31. a mutation may cause the enhancement of the specific wild type func
    gain of function mutation
  32. a gain of function mutations may be due to
    the increasing the quantity of the gene product
  33. a gain of function mutation is generally a dominant allele
  34. one copy of the mutant allele is sufficient to alter the normal phenotype
  35. W+ means its the wild type and is dominant
  36. when no allele dom, uppercase letters and subscripts designate alternate alleles
  37. cross between 2 parents with contrasting traits sometimes give rise to an intermediate phenotype in which neither trait is dom
  38. 1:2:1 ratio of incomplete dom 1 are the dom while the 2 is the partial dom
  39. homozygous recessives die from fatal lipid storage disorder what is the disorder and what is absent
    • tay sachs
    • hexosaminidas
  40. heterozygous of tay sachs appear normal but have a 1/2 W+ enzyme activity when compared to homo normal noncarriers
  41. this comes about if normal phenotypic expression occurs whenever a certain level of gene product attained
    threshold effect
  42. occurs when joint expression of 2 alleles of a gene in a heterozygote results in phenotypic detection of both gene products
  43. this express dom and rec and no blended phenotype
  44. when there are 3 or more alleles of the same gene in a population
    multiple alleles
  45. individuals can have up to 2 alleles for a single gene
    (diploid, homo X)
  46. any gene can be modified in multiple places/ways meaning
    each unique change produces a diff allele (not necessarily diff phenol)
  47. multiple alleles are studied in _____ not ______
    • pop
    • individuals
  48. when it comes to ABO blood groups, each individual is A,B,AB,or O phenotype as a result of these 2
    • dom
    • codom
  49. dom of blood group 2
    A and B
  50. codom of blood group
    A and B
  51. IAIA or IAi pheno
  52. IBIB or IBi pheno
  53. IAIB pheno
  54. ii pheno
  55. A and B antigens are controlled by a gene on which X
  56. to find the phenol of blood of individual is determined by
    mixing blood sample with antiserum containing type A and B antibodies
  57. When a person has A antigen only (A phenol)
    type A antibody causes clumping
  58. When a person has B antigen only (B phenol)
    type B antibody causes clump
  59. person has both antigens (AB phenol)
    both type A and B antibodies cause clumping
  60. person has neither antigen (O phenol)
    neither type A nor B antibodies cause clump
  61. if blood type A and placed in anti-A it will be spotted unlike when it is placed in B it is one large lump
  62. H substance is possessed by all blood antigens and is a precursor for both the A and B antigens
  63. the IA allele encodes an enzyme that can add what to the H substance
    N-acetylgalactosamine (AcGaNH)
  64. the IB allele encodes a modified enzyme that adds a what to the H substance
    terminal galactose
  65. the O phenotype when it comes it the H substance
    this results from the absence of either terminal sugar
  66. how can a woman have type O but one of her parents is AB and she has children who are type AB or B
    woman are found to be homo rec at the fucosy transferase (FUT1) locus which causes no fucose on H sub so no substrate to make A or B antigens
  67. heterozygotes may tolerate a nonfunctional mutant allele if W+ allele produces sufficient product for organism survival
  68. homozygotes for recessive allele may not survive
    recessive lethal allele
  69. lethal alleles represent "essential genes" lethal in homo state
  70. loss of func alleles can be recessive lethal
  71. sometimes recessive lethal allele may still be dom in respect to pheno
  72. time of death from a rec lethal allele is dependent upon when the gene product is essential to development
  73. agouti allele
    ag x ag = all ag
    ag x y = y and ag
    y x y = 2/3 y 1/3 ag
    mutant yellow dom over wt agouti
  74. homozygous mutant yellow is allele
  75. mutant allele always on
    gain of function
  76. deletion actually affects neighboring essential gene
  77. the dom lethal allele is lethal in both hetero and homo. therefore, these do not occur in humans
    T or F and why
    F because the lethal allele is only lethal in a homo state
  78. a mutation can be a dominant lethal allele meaning a hetero will not survive
  79. in a dom lethal allele both homo and hetero states are lethal and this is generally rare
  80. huntingtons disease is an ex of dom lethal allele
  81. people afflicted with huntingtons are hetero
  82. this disease causes nervous and motor system degeneration
  83. Huntington is exhibited after age 40, sometimes much earlier
  84. independent assort applies to situations in which 2 modes of inheritance occur at the same time
  85. two gene can undergo two modes o inheritance if
    the genes are controlling each character are not linked on the same X
  86. because 2 gene pairs and 2 modes of inheritance occur, the 9:3:3:1 ratio will be altered
  87. all unlinked loci will still follow mendels principle of independent assort
  88. even though 2 genes undergo 2 diff modes of inheritance, a regular punnett determine the phenol individually
  89. the prob of each phenol arising in a cross can be determined by fork lined or punnett only if
    assuming that the genes under consid undergo independent assort
  90. dihybrid cross w/2 loci having different patterns of inheritance
  91. phenotypes are often affected by more than one gene
  92. many traits characterized by a distinct phenol are affected by more than 1 gene
  93. the cellular func of numerous gene products contributes to the development of a common pheno
    gene interaction
  94. 3 ways epistais occurs
    • 1 gene pair or locus masks or modifies the effect of another gene pair or locus
    • 2 gene pairs complement each other such that one dom allele is required at each locus to express a certain phenol
    •  single dom allele at one locus may be epistatic to the expression of alleles at a second locus
  95. one gene pair/locus masks or modifies the effect of another gene pair/locus
    recessive alleles at one locus override expression of alleles at another locus
  96. one gene pair/locus masks or modifies the effect of another gene pair/locus
    • recessive alleles at one locus override expression of alleles at another locus
    • alleles at 1st locus are said to be epistatic to the masked alleles of the 2nd locus
    • the 2nd locus is hypostatic to the 1st locus
  97. 2 gene pairs complement each other such that one dom allele is require at each locus to express a certain pheno
    alleles at one locus may require specific allele at another locus, these pairs are said to complement each other
  98. the Bombay phenol for ABO groups is an example of epistasis
  99. 3 ways as to how Bombay pheno is an ex of epistasis
    • homo rec condition at 1 locus masks the expression of a 2nd locus
    • homo FUT1 or hh masks the expression of the IA and IB alleles
  100. homo mutant FUT1 is epistatic to the IA and IB alleles
  101. 2 diff Stanford and sfsu true wingless fly are generated, they are both morphologically identical. Is the mutation in each fly the same? what type of cross should be perform to figure this out?
    cross between both flies
  102. occurs when expression of a single gene has multiple phenotypic effects
  103. mutation in gene encoding connective tissue causing it to be weak in organs, eyes, spinal curve
    marfan syndrome
  104. mutation in which a person cannot metabolize porphyrin causing deep red urine and toxic to brain
    porphyria variegata
  105. genes present on the x X exhibit unique patterns of inheritance due to the presence of only 1 x X in males
  106. males have a single copy of most genes encoded by the x X, hemizygous
  107. eye color of drosph was first sample of x-linkage. What was the x linked mutant and how was it founded
    • white eyed mutant
    • inheritance pattern clearly related to the sex of the parent carrying allele and offspring
  108. lethal xlinked recessive disorders are observed only in males
  109. females can only be hetero carriers that do not develop disorders
  110. only females are carriers of recessive alleles. males are hemizygous
  111. specific pheno limited to one sex
    sex limited inheritance
  112. sex influences expression of pheno but not limited to one sex or another
    sex influenced inhertiance
  113. autosomal genes are responsible for contrasting pheno
  114. expression of the autosomal gene depends on the hormone constitution of the individual
  115. one pheno may be expressed in males and another in females
  116. sex limited inheritance example
    feathering in fowl
  117. cock feathering longer and more curved while hen is shorter and less curved.
    the single pair of autosomal alleles are reg by sex hormones
  118. HH Hh hh
    male and female
    • hen feathered
    • hen feathered
    • cock feathered

    Hen, hen, hen
  119. example of sex influenced inheritance
    pattern baldness in humans
  120. 4 characteristics of pattern baldness when it comes to sex influenced inheritance
    • autosomal genes responsible for contrast pehno
    • traits may be displayed by M and F
    • expression of the autosomal gene depends on the hormones of the individual
    • heter exhibits 1 pheno in 1 sex then contrasting pehno in the other
  121. BB Bb bb
    male and female
    • bald, bald, not
    • bald, not, not
  122. the % of individuals that show at least some degree of expression of the mutant geno defines
    penetrance of mutation
  123. example of penetrance
    if 15% of flies with the mutant geno appear wild type then the mutant gene has 85% penetrance
  124. the range of expression of the mutant geno relflects
    expressivity of mutant geno
  125. example of expressivity
    eyeless mutation reduction size from a partial red to complete elimination .25-.50
  126. occurs when genes affect the pheno produced by the gene in question
    gene suppression
  127. mutant allele at a locus partially or completely restores the W+ pheno of another locus homo or hemi for a mutant allele
  128. the physical location of a gene may influence its expression due to a position effect. 3 effects that occur
    • translocations
    • inversions
    • heterochromatin
  129. mutations affected by temp are called
    conditional sensitive mutations
  130. these kind of mutations are useful in studying mutations that affect essential processes
    conditional sensitive mutations
  131. an example of temp sensitive mutations
    mutant allele only expressed (P) at a lower temp
  132. nutritional mutations may prevent the pheno from reflecting the geno
  133. 2 nutritional mutations
    • prevent syn of nutrient molecules
    • auxotrophs (unable to syn nutrient molecules)
  134. phenotype from a nutritional mutation is expressed or not depending upon the diet
  135. this disease is due to the loss of enzyme to metabolize phenylalanine, need low phenylalanine diet
  136. this occurs when genes do not assort independently
  137. genes on the same X are linked and segregate with each other
  138. if complete linkage exists between 2 genes
    organisms heter at both loci are mated, a unique F2 pheno ratio designated the linkage ratio results
  139. involved the reciprocal exchange of X segments between homo (recombination)
    crossing over
  140. complete linkage or linkage w/o crossing over creates only
    parental gametes
  141. parental gametes produce
    however they don't produce
    • non-crossing over gametes
    • recombination between genes
  142. if crossing over between 2 linked genes occurs between 2 non sister chromatids this happened
    parental and recombinant gametes are produced
  143. is proportional to the degree of crossing over between little to no or frequent crossing over
    interlocus distance
  144. interlocus distance is crossing over between these 2 occurances
    • little to no crossing over between genes that are close
    • frequent even multiple crossovers between distant genes
  145. F2 phenol ratio is unique to 2 linked genes in cross of double hetero
  146. the ratio if completely linked for
    F1 x F1
    F1 x test cross parent
    • 1:2:1
    • 1:1
  147. 2 characteristics of linkage group
    • group of genes which show linkage
    • genes are on the same X
  148. in theory the number of linkage groups = n ( the haploid number of X)
  149. morgan discovered crossing over when studying 2 genes on x X in flies
  150. after crossing over was discovered morgan proposed these 2
    • the chiasmata visible on X were regions of crossing over
    • crossing over occurs between non-sister chromatids