Clinical Genetics

Question 1

what are autosomal chromosomes?

Answer 1

any chromosome that is not the X or Y chromosome

Question 2

what are alleles?

Answer 2

alternative forms of genes at the same position

Question 3

what are the types of alleles?

Answer 3

dominant
recessive
co-dominant

Question 4

what is epistasis?

Answer 4

non-allelic gene interaction

Question 5

what is non-allelic gene interaction called?

Answer 5

epistasis

Question 6

what does incomplete penetrance refer to?

Answer 6

blocking of genes by other genes

Question 7

what is it called when a gene is blocked by another gene?

Answer 7

incomplete penetrance

Question 8

how does variable expressivity occur?

Answer 8

modification of genes by other genes

Question 9

what does the modification of genes by other genes lead to?

Answer 9

variable expressivity

Question 10

why are some herding dogs more susceptible to drug toxicosis?

Answer 10

MDR1 dominant mutation

Question 11

what does the MDR1 dominant mutation in herding dogs lead to?

Answer 11

increased susceptibility to drug toxicosis

Question 12

how is the MDR1 gene mutation detected?

Answer 12

genetic testing

Question 13

why do greyhounds have a reduced capability to clear anaesthetic drugs?

Answer 13

mutation to cytochrome P450 gene

Question 14

can greyhounds be tested for the cytochrome P450 mutation?

Answer 14

no genetic testing available

Question 15

what are DEAs?

Answer 15

dog erythrocyte antigens - red cell surface antigens

Question 16

which DEA is the most antigenic?

Answer 16

DEA1 - responsible for serious transfusion reactions

Question 17

what percentage of dogs are DEA1 positive?

Answer 17

around 70%

Question 18

in what situations should blood cross-matching in dogs be performed?

Answer 18

unknown transfusion history

previous transfusion reaction

any previous blood transfusions

Question 19

how many alleles are there in the cat blood group system?

Answer 19

one gene locus

3 alleles - A, B and a rare AB

Question 20

which cat blood allele is dominant?

Answer 20

A

Question 21

which cat blood type is most common?

Answer 21

95% are A
5% are B
less than 1% are AB

Question 22

why should cats always be blood-typed before transfusion?

Answer 22

type B cats have a high titre of anti-A antibodies

Question 23

how does neonatal isoerythrolysis occur?

Answer 23

when type B cats are mated to type A/AB toms

type A kittens will receive anti-A antibodies in queens colostrum

Question 24

how is neonatal isoerythrolysis in kittens prevented?

Answer 24

blood type toms before mating

take kittens off cat for first 24-26 hours to avoid rich anti-A colostrum

Question 25

what is involved in the kennel club hip scheme (1965)?

Answer 25

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)

Question 26

what is the issue with the hip scoring scheme?

Answer 26

dogs with likely poor scores are not submitted - gives an inaccurate representation of pelvic issues within the breed

Question 27

what is involved in the kennel club elbow scheme?

Answer 27

medio-lateral radiographs taken of both elbows and judged by a panel of vet radiologists to calculate an estimated breeding value

Question 28

what is the eye scheme?

Answer 28

screening for 12 hereditary eye conditions in 65 breeds (list is dynamic and changing regularly)

Question 29

what are some of the conditions screened for under the eye scheme?

Answer 29

collie eye anomaly
lens luxation
glaucoma
progressive retinal atrophy

Question 30

what age does the eye scheme begin screening?

Answer 30

6-12 weeks

Question 31

what is the chiari malformation/syringomyelia (CM/SM scheme)?

Answer 31

MRI to screen for CM/SM in cavaliers and griffon bruxellois

dogs >1 years old

Question 32

what is chiari malformation?

Answer 32

fault in development of skull, causing part of brain to protrude from caudal opening

Question 33

what is syringomyelia?

Answer 33

presence of 1+ fluid-filled spaces in the spinal cord (syrinxes)

Question 34

which breeds are assessed under the respiratory function grading scheme?

Answer 34

french bulldogs, pugs and bulldogs

Question 35

what is involved in the respiratory function grading scheme?

Answer 35

assessor listens to breathing whilst calm and relaxed and then after 3 mins of fast-paced exercise
given grade between 0-3

Question 36

which grades are given in the heart scheme for cavalier king charles spaniels?

Answer 36

murmur grade 0/1/2/3+

mitral valve 0/1/2/3

Question 37

why does the heart scheme for cavalier spaniels exist?

Answer 37

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

Question 38

why are cats genetically tested?

Answer 38

usually in breeding programs - it is the only way to detect late onset diseases or carrier status before breeding

Question 39

which samples are taken from cats for genetic testing?

Answer 39

mouth swabs and/or blood samples

Question 40

what are some of the more common and important inherited disorders of cats?

Answer 40

blood group incompatibility/neonatal isoerythrolysis 
deafness 
glycogen storage disease type IV 
hypertrophic cardiomyopathy 
hypertrophic muscular dystrophy 
manx syndrome 
polycystic kidney disease 
progressive retinal atrophy