Clinical Genetics Flashcards
what are autosomal chromosomes?
any chromosome that is not the X or Y chromosome
what are alleles?
alternative forms of genes at the same position
what are the types of alleles?
dominant
recessive
co-dominant
what is epistasis?
non-allelic gene interaction
what is non-allelic gene interaction called?
epistasis
what does incomplete penetrance refer to?
blocking of genes by other genes
what is it called when a gene is blocked by another gene?
incomplete penetrance
how does variable expressivity occur?
modification of genes by other genes
what does the modification of genes by other genes lead to?
variable expressivity
why are some herding dogs more susceptible to drug toxicosis?
MDR1 dominant mutation
what does the MDR1 dominant mutation in herding dogs lead to?
increased susceptibility to drug toxicosis
how is the MDR1 gene mutation detected?
genetic testing
why do greyhounds have a reduced capability to clear anaesthetic drugs?
mutation to cytochrome P450 gene
can greyhounds be tested for the cytochrome P450 mutation?
no genetic testing available
what are DEAs?
dog erythrocyte antigens - red cell surface antigens
which DEA is the most antigenic?
DEA1 - responsible for serious transfusion reactions
what percentage of dogs are DEA1 positive?
around 70%
in what situations should blood cross-matching in dogs be performed?
unknown transfusion history
previous transfusion reaction
any previous blood transfusions
how many alleles are there in the cat blood group system?
one gene locus
3 alleles - A, B and a rare AB
which cat blood allele is dominant?
A
which cat blood type is most common?
95% are A
5% are B
less than 1% are AB
why should cats always be blood-typed before transfusion?
type B cats have a high titre of anti-A antibodies
how does neonatal isoerythrolysis occur?
when type B cats are mated to type A/AB toms
type A kittens will receive anti-A antibodies in queens colostrum
how is neonatal isoerythrolysis in kittens prevented?
blood type toms before mating
take kittens off cat for first 24-26 hours to avoid rich anti-A colostrum
what is involved in the kennel club hip scheme (1965)?
VD radiograph of pelvis/hips/femurs which is then judged by a panel of vet radiologists and given a score for each hip (lower = better)
what is the issue with the hip scoring scheme?
dogs with likely poor scores are not submitted - gives an inaccurate representation of pelvic issues within the breed
what is involved in the kennel club elbow scheme?
medio-lateral radiographs taken of both elbows and judged by a panel of vet radiologists to calculate an estimated breeding value
what is the eye scheme?
screening for 12 hereditary eye conditions in 65 breeds (list is dynamic and changing regularly)
what are some of the conditions screened for under the eye scheme?
collie eye anomaly
lens luxation
glaucoma
progressive retinal atrophy
what age does the eye scheme begin screening?
6-12 weeks
what is the chiari malformation/syringomyelia (CM/SM scheme)?
MRI to screen for CM/SM in cavaliers and griffon bruxellois
dogs >1 years old
what is chiari malformation?
fault in development of skull, causing part of brain to protrude from caudal opening
what is syringomyelia?
presence of 1+ fluid-filled spaces in the spinal cord (syrinxes)
which breeds are assessed under the respiratory function grading scheme?
french bulldogs, pugs and bulldogs
what is involved in the respiratory function grading scheme?
assessor listens to breathing whilst calm and relaxed and then after 3 mins of fast-paced exercise
given grade between 0-3
which grades are given in the heart scheme for cavalier king charles spaniels?
murmur grade 0/1/2/3+
mitral valve 0/1/2/3
why does the heart scheme for cavalier spaniels exist?
to assign each dog a risk of developing clinical MVD and a risk of passing the condition on to any offspring by a traffic light system
grades change depending on age
why are cats genetically tested?
usually in breeding programs - it is the only way to detect late onset diseases or carrier status before breeding
which samples are taken from cats for genetic testing?
mouth swabs and/or blood samples
what are some of the more common and important inherited disorders of cats?
blood group incompatibility/neonatal isoerythrolysis deafness glycogen storage disease type IV hypertrophic cardiomyopathy hypertrophic muscular dystrophy manx syndrome polycystic kidney disease progressive retinal atrophy
