Genetics Flashcards

1
Q

______________ traits have a MORE predictable inheritance.

A

single-gene

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2
Q

T/F: Very few traits are controlled by single genes and several other factors play a role in determining the final phenotype.

A

true

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3
Q

___________ is a term that describes symptoms, which may or may not be present in a dog with an at-risk or affected genotype. The dog has the mutated gene in the right number of copies to cause the disease, but the dog may not show physical symptoms of the disease. In other words, the gene may not have an impact on the individual unless certain environmental factors occur.

A

Incomplete penetrance

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4
Q

________ includes dogs with the mutation in the right number of copies to produce the disease.

A

At risk

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5
Q

T/F: you only need one copy of an autosomal dominant gene in order to express disease/trait

A

true

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6
Q

___________ is the proportion of dogs with a particular genetic variant (or gene mutation) who exhibit signs and symptoms of a genetic disorder aka express the phenotype.

A

penetrance

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7
Q

Why are both males and females equally affected by autosomal dominant traits?

A

because the gene is located on a non-sex linked chromosome.

these are rare in vet med.

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8
Q

What are 2 examples of autosomal dominants genes in vet med?

A
  1. polycystic kidney disease in persian cats
  2. progressive rod/cone degeneration/atrophy in english mastiffs and bull mastiffs
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9
Q

We in encounter autosomal recessive genes much more commonly in vet med. How many copies of the affected genes are required to express disease?

A

2

carrier = one mutant, one normal

affected = mutant, mutant

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10
Q

what are 2 examples of an autosomal recessive disease in vet med?

A
  1. congenital myasthenia gravis of smooth fox terries
  2. PRCD
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11
Q

If you breed a mutant/normal to a mutant/normal, what percentage of offspring will be AFFECTED by the autosomal recessive gene?

A

25% affected (mutant, mutant)
50% carriers
25% normal

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12
Q

What breed pairing would create 100% carriers of an autosomal recessive disease?

A

normal individual (normal, normal) bred to a affected individual (mutant, mutant)

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13
Q

Which breeding pairing would result in 50% affected offspring and 50% carrier offspring for an autosomal recessive disease?

A

carrier individual (mutant, normal) bred to an affected individual (mutant, mutant)

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14
Q

what is an example of complete penetrance in vet med?

A

myasthenia gravis of smooth fox terriers

100% of individuals with the affected genotype will have the disease / express the phenotype.

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15
Q

what are 2 examples of incomplete penetrance in vet med?

A
  1. hereditary cataracts of aussies
  2. Von willebrands disease in dobermans

only SOME individuals with the affected genotype will express the disease / phenotype.

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16
Q

what is an example in vet med of a polygenetic trait?

A

hip dysplasia – multiple loci are associated with disease and environmental factors play a large role in the expression of the phenotype.

17
Q

Hip dysplasia affected 71-75% of the canine population. What is the genetic predisposition to this condition?

A

joint laxity, which can be influenced by multiple factors such as genetics, the environment, and diet/exercise.

osteoarthritis is the secondary syndrome to occur.

18
Q

what is the difference between OFA and PennHip?

A

OFA – extended leg view only, reports as excellent, good, poor, or dysplastic; $250-300

PH – extended leg view, distraction index, and compares results within the breed, reports are more specific; $800

19
Q

T/F: dermatomyositis in a polygenic disease

A

true! 3 loci have been identified that result in the condition.
but this disease is also influenced by the environment.

20
Q

T/F: we should select breeding stock based on individual phenotype as opposed to generational influence.

A

false – select based on generational influence.

21
Q

T/F: it is ideal to breed weak individuals to strong individuals.

A

true

22
Q

T/F: minimizing poor environmental influences is ideal when considering reducing expression of some genetic traits.

A

true