5. Heritable defects in farm animals Flashcards
What is a phenocopy?
- Phenotype that is environmentally induced
- Single gene disorder mimicked by environmental influence.
- example = alpha-mannosidosis
Explain what alpha mannosidosis is (genetic basis and inheritance and phenocopy basis and symptoms)
- genetically recessive
- lysosomal storage disease in cats and cattle (ANGUS)
- It is a lethal disorder
How does it happen?
- Angus graze on a legume (locoweed)
- The plant produces an alkaloid( called swainsonine, and this inhibits alpha-D-mannosidase enzyme)
- oligosaccharides build up
- Results in neurological damage, head tremors, loss of muscle coordination, aggression
Give the name, mode of inheritance, phenotype and origin of CVM.
COMPLEX VERTEBRAL MALFORMATION
mode of inheritance:
- autosomal recessive
Phenotype:
- Only homozygotes effected
- misshaped vertebrae and scoliosis
Origin:
- 1999 in holstein
- caused by a single inbreeding bull
Give the name, mode of inheritance, molecular basis, phenotype and origin of BLAD.
BOVINE LEUKOCYTE ADHESION DEFICIENCY
Mode of inheritance:
- autosomal recessive
Molecular basis:
- single point mutation from A to G in position 383 of CD18 gene
- This caused a AA substitution from aspartic acid to glycine
- influenced the pathway for neutrophils required at infected site.
Phenotype:
- recurring bacterial infection of the soft tissue, delayed wound healing, stunted growth. Severe ulcers, chronic pneumonia, diarrhea and early death
Origin:
- can be tracked to a single bull (Osborndale Ivanhoe) used in 1950’s and 60’s
Give the name, mode of inheritance, molecular basis and phenotype of DUMPS.
Deficiency of uridine monophosphate synthase
Mode of inheritance:
- autosomal recessive
Molecular basis
- UMPS play a key role in pyrimidine nucleotide synthesis
- essential for normal growth and development
- point mutation (c to T), leads to loss of Ava 1 site restriction site in codon 405 of UMPS gene
Phenotype:
- low blood activity of enzyme,UMPS
- early embryonic death
- cant be identified by farmer and testing is required
- low prevalence in SA holstein herds
Give the mode of inheritance, molecular basis and phenotype of cutrullinemia.
Mode of inheritance:
- autosomal recessive
- it is rare, holstein and holstein-Friesian specific
Molecular basis:
- Deficiency in argininosuccinate synthetase (ASS): enzymatic disruption in the urea cycle
- single-base substitution (C to T): exon 5 of ASS
- CGA codon to TGA codon
- truncated peptide product: deprived functional activity
- accumulation of ammopnia: cannot be detoxified
Phenotype:
- severe neurological dysfunction
- unsteady gait
- apparent blindness
- head pressing
- calves die within 1 week
Give the mode of inheritance, molecular basis, phenotype and origin of spinal muscular atrophy. (progressive lethal disorder in brown swiss cattle)
mode of inheritance:
- autosomal recessive
Molecular basis:
- mutation in gene that makes 3-KDS-reductase activity: biosynthesis of glycosphingolipids
- gene mapped to telomeric region of chromosome 24
Phenotype:
- loss of balance in rear legs
- difficulty to stand
- calves lie down with front legs extended
- wasting away of muscle mass
origin:
- reported since mid 1980’s
- common sire: “meadow view destiny”
Explain bovine muscular hypertrophy…..
- increased in skeletal muscle size (hyperplasia rather than hypertrophy)
- Negative effects can lead to dystocia ( belgian blue born with caesarians)
- Myostatin gene (MSTN); responsible for double-muscle phenotype
- the muscular hypertrophy locus is on bovine chromosome 2
- It is partial dominance: single copy of mh = some double musceling, homozygou mh/mh is true double musceling phenotype
Characteristics of curly calf syndrome
- Name= Arthrogryposis Multiplex
- common in angus cattle
- genetically traced to popular bull “GAR precision 1680”
- happens because of gene deletion, which contains an essential gene
- results in a still born calf with a bent spine and very small size
Characteristics of hypotrichosis
- common in hereford
- non lethal defect
- autosomal recessive
- Happens in the Bovine Hairless gene (HR), SNP in HR gene ( A to G)
- Phenotype= partial/complete hair loss, calves have short curly coat and adults have sparse coat.
- these animals have higher incidence of skin infections
Characteristics of ideopathic epilepsy
- Common in hereford
- lethal
- calves get seizures from birth to 9 months
- mode of inheritance= simple recessive
- rare, occurs in less than 2% of the 18000 animals tested
What are the 3 types of dwarfism
1) Snorter dwarf
- short, compacted bodies with large heads
- have deformed sinus cavities, so its difficult to breath
2) long headed dwarfs:
- same body as snorters but normal size head
3) Bulldog dwarfs
- Bulldog shaped head, fat bodies, short legs
- die in utero or shortly after birth
Which genes are responsible for dwarfism in the following cattle breeds. Dexter, Angus, Hereford, Wagyu
DEXTER= "ACAN" gene, point mutation ANGUS= "PRKG2 (D2)" gene, point mutation HEREFORD= multiple genes WAGYU= different genes are responsible
In more detail explain Bulldog dwarfism
- Achondroplasia
- mode of inheritance= incomplete dominance (intermediate inheritance)(50% of each phenotype showed)
- one allele not completely expressed over the paired allele
- result is a third phenotype which is a combo of the phenotypes of both alleles
- homozygous: HH = aborted 6-8 months of the fetal stage
- Heterozygous: Hh= heavy muscled and small
Give the mode of inheritance, molecular, phenotype and origin of the spider lamb syndrome.
OVINE HEREDITARY CHONDRODYSPLASIA
mode of inheritance:
- autosomal recessive (semi lethal)
Molecular:
- single base change in fibroblast growth factor receptor (FGFR 3)
- FGFR 3 = negative growth regulator in bone growth
- Mutation found in ovine chromosome 6
- Heterozygotes may survive
Phenotype:
- skeletal deformities in lambs, bent legs, twisted spines, shallow bodies, flattened rib cage.
Origin:
- First observed in the 1970’s
- most common in Suffolk and Hampshire breeds
