ch12

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ch12
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2012-11-27 12:50:27
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bio exam2 ch12
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  1. Chromosome ---->______----->______---->______
    Chromosomes--->Genes---->Proteins---->Characters

    w/different traits alleles
  2. What are the combinations of Alleles??
    • Random Fertilization
    • Crossing over
    • Independent assortment
  3. What are the Forms of Genes??
    Alleles

    • -DNA copying mistakes
    • -mutagens
  4. Allelic variation and allele shuffling is the basis of _____,_____, and ____
    evolution, disease, and genetics
  5. Heredity
    transmission of traits from one generation to next
  6. Genetics
    scientific study of heredity
  7. What did Josef Kolreuter cross??
    he crossed tobacco strains to produce hybrids that differed from both parents
  8. What did T.A. Knight cross?
    • he crossed 2 varieties of garden pea, Pisum sativa
    •    -crossed 2 true-breeding strains
    •    -1st generation resebled only 1% strain
    •    -2nd generation resebled both (grandparents)
  9. Monohybrid Cross
    following one character
  10. Character
    heritable feature that varies among individuals
  11. Trait
    variant of a character
  12. True-Breeding 
    repeated generations have consistent traits, (self-fertilization)
  13. Hybrid
    offsprng of two different true-breeding varieties (cross-fertilization)
  14. True-breeding parents ='s
    P generation
  15. Hybrid offspring ='s
    F1 generation
  16. Mating of F1 plants (self fertilization) ='s
    F2 generation
  17. Mating of F2 plants (self-fertilization) ='s
    F3 generation
  18. Monohybrid crosses consists of ....
    only 2 variations (traits) of a single character
  19. Medel produced true-breeding of what...??
    • of pea strains for 7 different character
    •     -each character had 2 variants
  20. F1 Generation
    • -First filial generation
    • -offspring produced by crossing 2 true-breeding strains
    • -for every trait mendel studied, all F1 plants resembled only 1 parent 
    •        *referred to trait as dominant
    •        *Alternative trait was recessive
    • -No plants with characteristics intermediate btw the 2 parents were produced
  21. F2 Generation
    • -Second filial generation
    • -Offspring resulting from self-fertilization of F1
    • -Although hidden in F1, recessive trait had reappeared among some F2
    • -Counted proportions of traits
    •      *always found about 3:1 ratio of dominant: recessive
  22. 3:1 of dominant to recessive in _____?
    F2 

    • -3/4 plants w/ dominant form
    • -1/4 plants w/ recessive form
    • - dominant to recessive ratio was 3:1
  23. Mendel Discovered that the ratio is actually _____??
    1:2:1

    • -1true-breeding dominant plant
    • -2 not-true-breeding dominant plants
    • -1 true breeding recessive plant
  24. What did Mendel Conclude??
    His plants did not show intermediate traits (each trait is intact, dicrete, not blended)

    For each character, one trait was dominant, other recessive

    Pairs of alternative traits examined were segregated among progeny of a particular cross

    Alternative traits were expressed in F2 generation in raio of 3/4 dominant to 1/4 recessive
  25. Homozygous
    2 of the same allele

    both alleles for a gene are identical (TT, tt)
  26. Heterozygous
    gene has 2 differnt alleles (ex Tt)
  27. Recessive (trait or allele)
    phenotype observed only when two copies of allele (homozygous) (tt)
  28. Dominant (trait or allele)
    phenotype observed when homozygous or heterozygous (TT, Tt)
  29. Phenotype
    physical, biochemical, physiological traits of an individual based on genotype
  30. Homologous Chromosomes 
    Two versions of each chromosome 

    • -genes for characters at specific loci on chromosome
    • -forms of genes = alleles
  31. Principle of Segregation
    Two alleles for a gene segregate during gamete formation and are rejoined at random, one from each parent, during fertilization 

    physical basis for allele segregation is the behavior of chromosomes during meiosis
  32. what does Chromosome theory of inheritance state??
    States that ..

    • -genes are located at specific positions on chromsomes
    • -behavior of chromosomes during meiosis and fertilization account for inheritance patterns
  33. What do chromsomes undergo...??
    Chromosome undergo segregation andindependent assortment during meiosis to account for mendel's observations, conclusions and 5-element model
  34. Dihybrid Cross
    mating of parental varieties differing in two characters

    1. do the traits of two characters remain together: dependent Assortment

    2. Do the traits of two characters separate: independent Assortment
  35. In Characters studied, inheritance of one character has no effect on the inheritance of another Why??
    each pair of alleles for a given character segregates independently of the other pair during meiosis 

    ='s Law of Independent Assortment
  36. a Dihybrid cross ratio of 9:3:3:1 if genes are on ______???
    different chromosomes
  37. Probability scale ranges from ___ to ___
    0 to 1

    • -Event certain to occur: probability of 1
    • -Event that is certain not to occur: probability of 0
    • -The probabilities of all possible outcomes for an event must ass up to 1
  38. SsYyAa * SsYyAa 

    what is the probability that an offspring will be homozygous recessive for all three genes???
    Ss *Ss: probability of ss offspring = 1/4

    Yy *Yy: probability of yy offspring = 1/4

    Aa *Aa: probability of aa offspring = 1/4
  39. Apply rule of multiplication to calculate the probability offspring will be ssyyaa???
    1/4 ss * 1/4 yy * 1/4 aa = 1/64
  40. Testcross
    to determine genotype of individual w/ dominant phenotype

    -Cross individual w/ unknown genotype (ex B_) w/ a homozygous recessive (bb)

    -phenotype ratios among offspring are different, depending on genotype of unknown parent 
  41. Dominant heterozygote (Aa) displays what??
    displays the dominant phenotype
  42. Recessive phenotype expressed when _____ copies (aa) are present 
    2 copies aa are present
  43. Dominant doe not imply _____ or more common than a recessive 
    Dominant does not imply normal or more common than a recessive
  44. Wild-type traits (those prevailing in nature) are _______??
    not necessarily specifies by dominant alleles
  45. Monogenic
    Many inherited disorders in humans are controlled y one gene
  46. Monogenic inherited human disorders ='s 
    monohybrid
  47. Recessive inheritance need what??
    • -2 recessive alleles are needed to show disease
    • -Heterozygous parents
    • -probability of inheritance increases w/ inbreeding, mating btw close relatives
  48. Dominant inheritance requires what???
    • -One dominant allele is needed to show disease
    • -Dominant lethal alleles are usually eliminated from the population
  49. What is controlled by a single gene locus??
    Over 10,000 monogenic human genetic disorders, dominat or recessive traits
  50. What is the majority trait in inherited human disorders??
    Majority are recessive
  51. What is the Range in severity in inherited human disorders??
    relatively harmless conditions (free/attached earlobe) to severe (HD, CF, hemophillia etc)
  52. Most people w. recessive disorders are born to ______ heterozygous parents (carriers)
    are born to normal heterozygous parents
  53. What kind of disorder is Cystic Fibrosis??
    • -A Recessive Disorder
    • -Most common lethal genetic disease in US
  54. What is Cystic Fibosis characterized by??
    an excessive secretion of very thick mucus from lungs, pancreas, and other organs
  55. What is the risk of CF in caucasion population when allele carred by 1 in 25 caucasions w/ a chance that 2 caucasian carriers marry??
    1/25* 1/25 = 1/625
  56. What is the risk of CF in caucasion population when allele carred by 1 in 25 caucasions w/ a chance that 2 carriers will be homozygous recessive???
    Cc * Cc ='s 1/4
  57. What kind of disorder is Achondroplasia??
    a form of dwarfism and Dominant Disorder

    -only heterozygotes display phenotype

    -homozygous dominant genotype is embryonic lethal
  58. Why are Dominant lethal alleles rarer than recessive lethal alleles??
    • -Recessive alleles have normal heterozygote carriers
    • -Dominant alleles cannot be carried by heterozygotes w/o affecting them
    • -Many lethal dominant alleles result from mutations in a sperm or egg that kill embryo
  59. Mendel's model of inheritance assumes that ....??
    • -each character is controlled by a single gene
    • -each gene has only 2 alleles
    • -there is a clear dominant-recessive relationship btw the alleles

    Most genes do not meet these criteria
  60. Incomplete Dominance
    heterozygous phenotype is intermediate to homozygous phenotypes
  61. Hypercholesterolemia
    incomplete dominance in humans

    • -dangerously high levels of blood cholesterol
    • -heterozygotes have blood cholesterol levels about twice normal
    • -homozygotes have blood cholesterol levels about five times normal
  62. Codominance
    neither allele is dominant to the other, both are expressed if present

    heterozygote shows some aspect of phenotypes of both homozygotes
  63. Incomplet dominance
    heterozygote is intermediate in phenotype btw 2 homozygotes
  64. Multiple Alleles
    may br more than 2 alleles for a gene in a population (ABO blood types)

    Each individual can only have 2 alleles

    For any given gene, usually more than two alleles exist
  65. Quantitative Genetics
    When genes and enviornment interact

    • Continuous variation
    • Heritability
  66. Continuous variation
    variation due to both genetic and environmental difference 

    • Large range of phenotypes
    • Ex. height, weight, intelligence, cancer susceptibility
  67. Heritability
    proportion of the variation w/in a population due to genetic differnce among individuals
  68. Mean
    average: sum of all phenotypic values divided by number of individuals
  69. Polygenic Inheritance
    occurs when multiple genes are responsible for controlling phenotype

    Phenotype is accumulation of contributions by multiple genes

    Characters show continuous variation (quantitative)


    multiple genes turn into a single character (skin color)
  70. Pleiotrophy
    impact of a single gene on more than one character, symptoms

    Sickle cell disease exhibits pleiotrophy
  71. What are the characterisrics to get Sickle cell disease
    Heterozygotes are normal carriers (recessive traits)

    Causes disk-shaped rbcs to deform into a sickle shape w/ jagged edges
  72. Who are carriers of the sickle cell trait??
    heterozygotes (Ss): usually healthy, can experience pleiotropic effects in low O2
  73. what is the difference btw Pletotrophy and Polygenic inheritance??
    Pleiotrophy uses a Single gene to produce multiple characters

    Polygenic inheritance uses multiple genes to produce a single character (skin color)
  74. Pleiotrophy refers to an allele which has ...??
    more than one effect on the phenotype
  75. Pleiotrophic effects are difficult to predict b/c???
    because a gene that affects one trait often performs other, unknown function

    • This can be seen in human diseases such as CF or sickle cell anemia
    •      -multiple symptoms can be traced back to one defective allele
  76. Epistatis
    interaction btw genes at two or more loci (phenotype differs from expected if the loci were expressed independently)

    •     -R.A. Emerson crossed 2 white varieties of  corn
    •           -F1 was all purple
    •           -F2 was 9 purple : 7 white

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