Genetics Flashcards
define gene loci
defined positions of the gene on the chromosome
define autosomal chromosomes
chromosomes that arent X or Y
what is meant by linked genes?
genes close together on chromosomes
what is meant by sex linked genes?
genes on sex chromosomes
define allele
alternative forms of genes with same locus
what are the different forms of alleles?
dominant
recessive
co-dominant
define epistasis
non-allelic gene interaction
what causes incomplete penetrance?
genes being blocked by other genes
what leads to variable expressivity of genes?
genes being modified by other genes
what is significant about manx cats genes?
variable expression and lethal genes due to mutation causing short tails
what does the M allele cause in manx cats?
absence of tail
affects spine and cord, continence and control of back legs
what is the characteristic of M allele in manx cats?
high but variable penetrance
lethal gene
what does the presence of Mm or MM genes mean for manx cats?
Mm- defected tail of variable length
MM- die in utero
how should you reduce problems in manx cats?
avoid breeding tailless cats together or any affected cats
how is coat colour in labradors determined?
epistatic interactions of Ee and Bb genes
what does the Ee gene in labradors determine?
presence of eumelanin
E- has pigment
e- doesn’t have pigment
what does the Bb gene in labradors determine?
pigment concentration of eumelanin
B- presents black
b- presents brown
what colours of labradors are seen with each combination of Ee and Bb genes?
eebb- yellow fur, brown nose, lips and eye rims
eeB_- yellow fur, black nose, lips and eye rims
E_bb- chocolate fur, nose, lips, eye rims
E_B_- black fur, nose, lips, eye rims
what are the features of genes for tortoise shell cats?
sex linked and epistatic effects
what causes tortoise shell colouring?
fur being mix of ginger and black tabby
what is significant for orange fur gene?
sex linked to females
epistatic to autosomal black and tabby genes
describe how fur colour is determines in tortoise shell cats
they are heterozygous for orange gene with one X having orange colour/X^O and the other not having it/X^-
in each cell one X is randomly turned off so hair is colour of turned on gene
why does MDR1 dominant mutation affect drug sensitivity?
affects P glycoprotein involved in transport across BBB and excretion so drugs build up and potentially become toxic
what breeds are prone to MDR1 mutation?
herding dogs
what drugs are affected by MDR1 mutation?
ivermectin
milbemycin
selamectin
why do greyhounds take longer to recover from anaesthesia?
gene mutation for expression of cytochrome P450 which is responsible for anaesthesia clearance
define antigenicity
likelihood immune system will react and make antibodies against a substance
what is responsible for antigenicity in dog blood types?
genetically determined markers on RBC surfac
what are DEAs?
red cell surface antigens
what are most dog patients blood types?
DEA positive
what determines if dogs are DEA positive or negative?
variation of density of DEA 1 on RBC surface
what should be done before giving dogs blood?
cross matching
what blood type should you give to dogs if blood type unknown and why?
DEA negative to prevent reactions
what determines cat blood types?
one gene locus
what are the possible alleles for cat blood type and how do they relate to each other?
A- dominant
B- recessive
AB- recessive to A, co-dominant to B
what is the prevalence of each cat blood type?
95% A
5% B
less than 1% AB
why is it vital to cross match or blood type cats before transfusing?
high amounts of naturally occurring antibodies against other blood types
describe how neonatal isoeryhtrolysis happens
type B cat mates with type A tom so type A kitten receives antibodies in colostrum which can be fatal
how can neonatal isoerythrolysis be prevented?
blood type toms before mating
what is the purpose of screening programs?
provide recommendations for suitability of breeding
what is the purpose of the hip scheme?
address hip dysplasia
how is hip screening done?
VD radiographs of pelvis and femurs judged and scored out of 53
lower the score the better
combined with health assessment to calculate breeding value
what is the purpose of the elbow scheme?
address elbow dysplasia
how is elbow screening done?
mediolateral radiographs of each elbow
judged and scored 0-3
used to calculate breeding value
what is the purpose of the eye scheme?
screen for 12 hereditary eye conditions in 65 breeds throughout breeding life
define chiari malformation
fault in skull development causing brain to protrude out of back of skull
define syringomyelia
one or more fluid filled pockets that may develop in spinal cord called syrinxes
how is CM/SM screened for?
MRI graded
tested once over 1 year old
how do you grade respiratory function?
listening to breathing while calm then after 3 minutes exercise
graded 0-3
what is seen in grade 0 respiratory function?
clinically unaffected
free of respiratory signs of BOAS
what is seen in grade 1 respiratory function?
clinically unaffected but mild respiratory signs
what is seen in grade 2 respiratory function?
clinically affected
moderate respiratory signs of BOAS
monitor as may need vet attention
what is seen in grade 3 respiratory function?
clinically affected
severe respiratory signs of BOAS
need vet treatment
dont breed from
what is assessed in heart scheme for CKCS?
murmur grade and mitral valve prolapse 0-3
risk of developing MVP and passing on to offspring
what is the main way to genetically test cats?
cheek swabs
