CB13 Gene Mutations & Inherited Disease

Question 1

Explain the nature of genetic diseases in animals

Answer 1

Inheritance of a particular disease can be suspected if:
- higher incidence in some breeds or breeding lines
- after removing environmental factors it is still present

Question 2

List the main types of gene mutations

Answer 2

Point mutations
- transition: purine to punne
- transversion: purine to pyrimidine

Translocation, deletion, duplication…
- chromosomal rearrangements
- usually severely deleterious

Question 3

Describe autosomal dominant & give examples of diseases

Answer 3

• affects equally males & females
• mutated allele is dominant (heterozygous will be affected)
• does not skip generations

e.g. Lack of tail in Manx cats, comb form in chickens

Question 4

Describe autosomal recessive & give example of disease

Answer 4

• Affects equally male & female
• mutated allele is recessive heterozygous animals are not affected)
• skips generation (non-affected carriers)

e.g. Double muscling in cattle, malignant hyperthermia syndrome in pigs

Question 5

Describe x-linked recessive & give examples of the disease

Answer 5

• Mutation in sex chromosome X
• mutated allele is recessive
• all males that carry mutated X are affected
• females can be affected or carriers
• can’t be transmitted sire → male offspring

e.g. Haemophilia

Question 6

Describe sex-limited inheritance & give an example of disease

Answer 6

• Mutation in an autosome
• only one sex express the phenotype

e.g. Cryptochidism in dogs

Question 7

Describe polygenic disease & give an example

Answer 7

• Several genes plus the environment cause the phenotype
• observed in groups that share genes & an environment

e.g. Hip dysplasia in dogs