Genetics

Question 1

Genotype

Answer 1

genetic makup of a individual

Question 2

Heterozygous

Answer 2

have 2 different forms of a gene for specific trait/dz

Question 3

Homozygous

Answer 3

have 2 identical forms of a gene for specific trait/dz

Question 4

Penetrance

Answer 4

proportion of genetically affected individuals that express a trait + extent that trait is present
o = likelihood that a given gene will result in dz
o Incomplete suggest <100%

Question 5

Phenotype

Answer 5

observable characteristics resulting from interaction of genetic makeup and environment

Question 6

Polygenic

Answer 6

trait/dz caused by 2 or > genes

Question 7

Autosomal recessive

Answer 7

• Carried on autosomal chromosome
• Both copies of mutation have to be present

Question 8

Pedigree evaluation autosomal recessive

Answer 8

o Skips generations → parents can be asymptomatic carriers
o No sex predilection
o Mating of silent carriers (heterozygotes) parents → 25% affected phenotype, 75% not
o Mating of 2 affected parents → 100% affected offspring

Question 9

Autosomal dominant

Answer 9

• Only 1 copy of mutation necessary for clinical phenotype
  o Homozygote or heterozygote

Question 10

Predigree eval Autosomal dominant

Answer 10

o At least 1 affected parent
 Heterozygous → 50% affected offspring
 Homozygous → 100% affected offspring
o No sex predilection

Question 11

X-linked

Answer 11

• Gene carried on X chromosome
• Most commonly recessive
  o Males almost always show phenotype since only 1 X
  o Females can be silent carriers unless both X’s carry mutation

Question 12

Pedigree eval X linked

Answer 12

o Affected males > females
o Affected males crossed w normal female → silent (unaffected) females
o Silent carrier females pass the trait to 50% male offspring
o Affected male crossed w silent carrier female → can result in affected female
 Uncommon

Question 13

Polygenic

Answer 13

• 2 or > genes working together to develop a specific trait
• Many inherited dz in vetmed

Question 14

Incomplete penetrance

Answer 14

• <100% of individuals with mutation will have clinical trait/dz
• Variable expressivity of trait → severity of phenotypic expression

Question 15

Which diseases are proven heritable?

Answer 15

Endomyocardial fibrosis
ASD
PDA
PS
SAS
TOF
TVD
VSD

Question 16

Breeds endomyocardial fibrosis

Answer 16

Siamese
Burmese
Colony of DSH

Question 17

Pattern of inheritance endomyocardial fibrosis

Answer 17

Unknown

Question 18

What is endomyocardial fibrosis

Answer 18

Rare feline CHD
* LA and LV dilation
* Severe endocardial thickening

Question 19

ASD breeds

Answer 19

Boxers
Doberman
Samoyed
Standard Poodles

Question 20

ASD pattern of inheritance

Answer 20

Autosomal dominant more likely

Question 21

ASD pedigree studies

Answer 21

• Pedigree evaluation performed in Poodle and Doberman
• Ostium secondum defect for both
• Hu: 2 transcription factors identified
• GAT4A and NKC2.5
• Not identified in dogs

Question 22

PDA breeds

Answer 22

Poodle

Question 23

PDA pattern of inheritance

Answer 23

Polygenic

Question 24

PS breeds

Answer 24

Scottish Terriers
Wire-haired terriers
Miniature schnauzers
Beagles

Question 25

PS pattern of inheritance

Answer 25

Polygenic

Question 26

PS studies genetics

Answer 26

- Only studied in Beagles - Specific gene mutation not identified

Question 27

SAS breeds

Answer 27

Newfounland Golden retreivers Rottweiler

Question 28

SAS pattern of inheritance

Answer 28

Polygenic

Question 29

SAS studies genetics

Answer 29

Mostly studied in Newfoundland

Question 30

TOF breeds

Answer 30

Keeshond

Question 31

TOF pattern of inheritance

Answer 31

Polygenic

Question 32

TOF studies genetics

Answer 32

- Spectrum of defects - Genetic linkage to 3 canine chromosomes - Hu: conotruncal defects * Zinc finger protein multitype 2 (ZFPM2) * Modulator of GATA transcription factor

Question 33

TVD breeds

Answer 33

Labs

Question 34

TVD pattern of inheritance

Answer 34

Autosomal dominant with reduced penetrance

Question 35

TVD genetic studies

Answer 35

Linked to an area on chromosome 9 No specific gene mutation identified

Question 36

VSD breeds

Answer 36

Lakeland Terriers WHWT English Spinger Spaniel Basset Hounds Beagle

Question 37

VSD pattern of inheritance

Answer 37

Autosomal recessive (beagles) Autosomal dominant w incomp. penetrance OR polygenic (Springer Spaniels)

Question 38

Gene for ARVC

Answer 38

Striatin gene