Lecture 21 4/22/24

Question 1

What does congenital mean?

Answer 1

present at birth

Question 2

What does genetic mean?

Answer 2

caused by abnormal DNA; hereditary

Question 3

What is the pathogenesis of storage diseases?

Answer 3

-mutation occurs in DNA coding a necessary enzyme
-substrate is not degraded by enzyme
-substrate accumulates within many cells of the body
-results in multi-organ enlargement and dysfunction

Question 4

Which cells are most susceptible to accumulation in storage diseases?

Answer 4

neurons

Question 5

What are the characteristics of lysosomal storage diseases?

Answer 5

-most defective enzymes are lysosomal enzymes
-substrate accumulates within lysosomes

Question 6

What are the characteristics of beta mannosidosis?

Answer 6

-lysosomal storage disease in salers cattle
-neonatal tremors and head bobbing
-domed skull and narrow palpebral fissures
-death within weeks of birth
-vacuolated neurons, renal epithelium, and macrophages

Question 7

What are the characteristics of mucopolsaccharidosis VI?

Answer 7

-lysosomal storage disease in siamese cats
-severe form leads to skeletal abnormalities, facial dysmorphism, and kyphosis
-eventual paraparesis develops
-mild form causes degenerative joint disease of shoulder and stifle

Question 8

What is the clinical significance of storage diseases?

Answer 8

-rare diseases that often cause death before weaning
-majority are autosomal recessive
-difficult diagnosis; urine metabolite screening, genetic testing, or necropsy
-used as animal models to study human disease

Question 9

What counts as close inbreeding?

Answer 9

-brother/sister
-father/daughter

Question 10

What counts as line breeding?

Answer 10

grandfather/granddaughter

Question 11

What are the results of inbreeding?

Answer 11

-increased homozygosity/expression of recessive genes
-decreased fertility
-decreased size
-decreased immunocompetence

Question 12

What are the characteristics of dwarfism?

Answer 12

-bowed limbs/degenerative joint disease
-rapid intervertebral disk degeneration
-dominant mutation affecting fibroblast growth factor 4

Question 13

Why is it important that the mutation for short legs is on one chromosome, and the mutation for intervertebral disk disease is on another?

Answer 13

it is possible to breed away the intervertebral disk disease while maintaining the short leg look

Question 14

What are the characteristics of Scottish fold cats?

Answer 14

-have a dominant gene for cartilage defect
-heterozygotes have folded ears, and legs and tails that are short and thick
-homozygotes develop ankylosing degenerative joint disease by 4-6 mo. of age; do not survive to adulthood

Question 15

What are the characteristics of muscular hypertrophy?

Answer 15

-excess muscle development
-aim of selective breeding in meat breeds
-myostatin gene mutation in cattle, sheep, mice, and whippets

Question 16

What are the results of generalized striated muscle hypertrophy?

Answer 16

-dystocia/require caesarian section
-higher calf mortality; low body fat, lower feed intake, slower growth
-euthanasia of affected whippets that do not met breed standard

Question 17

What are the characteristics of dermoid sinus/cyst?

Answer 17

-fibrous cord/track/cyst connecting skin and spinal canal
-most common in Rhodesian ridgeback
-dominant genetic defect creates ridge
-homozygous (RR) dogs are more likely to develop cyst defect
-gene is involved in both hair follicle orientation and neural tube closure

Question 18

What are the characteristics of hydrocephalus?

Answer 18

-dilation of brain ventricles
-breed standard for chihuahua

Question 19

What are the characteristics of hypodontia?

Answer 19

-partial absence of teeth
-breed standard for xoloitzcuintli

Question 20

What are the characteristics of hairless, toothless dogs?

Answer 20

-developmental failure indicates ectodermal defect
-heterozygotes; homozygous state is lethal in utero

Question 21

What are the characteristics of congenital aganglionosis?

Answer 21

-occurs in completely white foals of overo paint parents
-absence of neural ganglia in colon leads to a lack of peristalsis; functional obstruction +/- dilation
-due to failure of migration of neural crest cells
-all “frame” overo horses are heterozygous for mutation

Question 22

What are the characteristics of ectropion?

Answer 22

-eversion of the eyelids
-results in exposure of the eye and possible irritation
-breed standard in basset hound, bloodhound, cocker spaniel, others