vet-tech-therio-ch-3

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Author:
darlene.m.nelson
ID:
103918
Filename:
vet-tech-therio-ch-3
Updated:
2011-09-23 23:05:31
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vet tech theriogenology chapter Simple Mendelian patterns inheritance set
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vet tech theriogenology chapter 3 Simple Mendelian patterns of inheritance set
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  1. Character (trait)
    • genetic (heritable) or due to external factors (non-genetic in origin)
    • eg tail-less cat
    • 1. due to trauma - can't pass characteristic to offspring
    • 2. Manx cat - genetically inherited - can pass characteristic to offspring
  2. Phenocopy
    an external or environmental factor produces a phenotype identical to that produced by a gene
  3. Characteristic caused by genes
    • incidence of that characteristic will be higher in related individuals
    • related individuals more likely to have similar genes
  4. Types of gene action
    • autosomal dominant
    • autosomal recessive
    • sex-linked dominant
    • sex-linked recessive
  5. Pedigree
    • can help to determine if characteristic is genetic
    • need enough of a pedigree (big enough statistical sample) to be able to determine
  6. Autosomal dominant genes
    • characteristic caused by the dominant gene will be expressed in every individual carrying the gene
    • 1. defect carried from generation to generation w/o skipping a generation
    • 2. every affected offspring must have one affected parent (except mutations)
    • 3. normal offspring from affected parents cannot pass on the condition
    • 4. condition will affect an equal # of males and females
    • 5. normal individual crossed with heterozygous affected individual can produce an affected individual
    • affected = AA or Aa
    • normal = aa
  7. Autosomal recessive genes
    • recessive genes will only be expressed in individuals with 2 copies (homozygous for that gene)
    • if individual has only 1 copy, gene can be passed from generation to generation w/o being revealed until an individual receives 2 copies of the gene and the condition is expressed
    • 1. the diorder may skip a generation
    • 2. all offspring of 2 affected parents will be affected (offspring homozygous)
    • 3. equal # of males and females affected
    • 4. in rare disorder
    • 4a. most affected individuals will have normal parents (heterozygous carriers)
    • 4b. most normal parents producing affected offspring will be more closely related than other animals in population as they must carry recessive (rare in rare disorder)
    • 4c. if both parents heterozygous carriers - 1 in 4 offspring affected
    • 4d. matings between an affected and unrelated normal animal will produce only normal offspring (carrier)
    • affected = aa
    • normal = AA
    • carriers = Aa
  8. X-linked dominant genes
    • located on the X chromosome
    • 1. all animals carrying the gene will express it, normal individuals will not carry it
    • 2. every affected offspring must have at least one affected parent
    • 3. affected males mated to normal females will not pass the gene to any of their sons
    • 4. affected males mated to normal females will pass the gene to all their dauhters
    • 5. rare condition - incidence of defect or disease in females is 2x that in males
    • affected = X(A)X(A), X(A)X(a), X(A)Y
    • normal = X(a)X(a), X(a)Y
  9. X-linked recessive genes
    • located on the X chromosome
    • in male, recessive X can be expressed because there is no 2nd dominant gene copy to maske the
  10. recessive
    • 1. defect may skip a generation
    • 2. all offspring of 2 affected parents will be affected
    • 3. incidence is lower in females than males
    • 4. rare condition
    • 4a. most affected individuals will be males
    • 4b. will result from normal parents (female will be carrier)
    • affected = X(a)X(a), X(a)Y
    • normal = X(A)X(A), X(A)Y
    • carriers = X(A)X(a)
  11. Pedigree Analysis
    • can indicate whether carrying a dominant gene
    • can indicate whether homozygous for a recessive gene
    • difficult to determine from a pedigree and it phenotype if an animal is carrier of recessive gene

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