Exam 1: Genetics

Question 1

Heritability estimates are used to

Answer 1

Evaluate the strength of inheritance for each trait

Question 2

the percent variation in performance due to genetic effects

Answer 2

Heritability

Question 3

are reproductive traits maternal or terminal

Answer 3

maternal

Question 4

reproductive traits heritability and environmental impact

Answer 4

low heritability
big environmental impact

Question 5

terminal traits heritability

Answer 5

moderate to high heritability

highly heritable trait ex: backfat depth

Question 6

Why are genetic abnormalities seen so often in pigs

Answer 6

large litters are born at a time and often= more chances for abnormalities

Question 7

abnormalities

Answer 7

deviations from normal development
can involve any part of the pig

-can impair pigs ability to function or even cause death
-internal or external

Question 8

anatomical abnormalities or defect occur in at least _____% of newborn pigs

Answer 8

1%

Question 9

Not all abnormalities are of genetic origin. What are some other possible causes of abnormalities

Answer 9

environmental (viral infection, nutrition, certain drugs)

Question 10

simple recessive

Answer 10

Two copies of a gene are required for the trait to be expressed

-homozygous dd
-dd affected
-Dd carriers

**most common in pigs
ex: stress syndrome

Question 11

simple dominant

Answer 11

only one copy of the gene is required to produce the defect
- D_
-weeds itself out

ex: Napole

Question 12

sex-link recessive

Answer 12

found only on the X chromosome since Y has few active genes

tend to be recessive but MALES will exhibit more often than females

ex: colorblindness in humans

Question 13

sex-limited

Answer 13

occurs only in one sex because it is related to sexual difference
-recessive or dominant

ex: cryptorchid or scrotal hernia

Question 14

syndactyly

Answer 14

presence of only 1 toe per foot rather than 2

inherited as a single dominant gene

nearly eliminated from U.S population

“mulefoot”

Question 15

polydactyly

Answer 15

presence of extra toes and/or dewclaws

fairly common in swine

little economic value (doesn’t affect market, not good for show)

Question 16

splayleg

Answer 16

most common leg disorders seen in young pigs

rear legs are most often affected but can be forelegs

caused by incomplete development of muscle fibers in the front and rear legs

genetic OR environment (viral, slippery floor, nutrition)

Question 17

umbilical hernia

Answer 17

“belly rupture” /”belly bust”

Individuals may die during growth due to strangulation of the intestines but most reach market

genetics OR environment (naval infection/staph)
***environment is more common reason

male or female

Question 18

scrotal hernia

Answer 18

sex-limited condition in males (2 pairs of recessive genes)

Weakness in muscles surrounding the inguinal canal occurs, allowing intestines to drop into the scrotum

usually not fatal

**can be influenced by maternal or environemt
**CANNOT CASTRATE; sent as it to packing plant

Question 19

nipple abnormalities (2)

Answer 19

inverted nipples
blind nipples

Question 20

inverted nipples

Answer 20

teat canal is held inward forming a small crater so normal milk flow is prevented

-failure of the nipple to protrude from udder surface

“pin” nipples

always genetic

Question 21

blind nipples

Answer 21

no visible nipple/canal

caused by environment (injury, irritation, scabbing due to rough floors)

Question 22

hermaphrodites

Answer 22

have both female and male sex organs (genetic or environment)

normally genetically female but have a portion of male sex organ

may have: tipped vulva or vestigial sheath

Question 23

how do hermaphrodites occur

Answer 23

large litters due to uterine crowding (share common blood supply due to placenta joining)

Question 24

cryptorchidism

Answer 24

sex-limited inheritance with at least two gene pairs contributing to the defect

one or both testicles retained in the boars body cavity

Question 25

if both testicles in a cryptorchid are retained, the boar is ______

Answer 25

sterile

Question 26

atresia ani

Answer 26

rare pig born without rectal opening boars= fatal gilts= semi fatal

Question 27

females with no anal opening can defecate through _________ and grow normal

Answer 27

vulva

Question 28

if prevelence of atresia ani is high, you should cull what

Answer 28

sire dam littermates affected individual

Question 29

Rendement Napole causes pork to have

Answer 29

low pH paler color lower water holding capacity greater cooking loss

Question 30

what breed is Napole normally seen in

Answer 30

hampshire hampshire crosses

Question 31

is Napole dominant

Answer 31

yes, complete dominant (RN-) single locus with 2 possible allels: (RN- or rn+)

Question 32

the dominant allele in Napole is responsible for

Answer 32

Elevated glycogen stores in the muscle that results in increased production of lactate reduced pH in muscle

Question 33

Porcine stress syndrome (PSS)

Answer 33

also called malignant hyperthermia, transport myopathy, halothane gene triggered by stress or excitement simple recessive inheritance primary pietrain/ pietrain crosses not always fatal

Question 34

signs of porcine stress syndrome

Answer 34

tremors of tail/back/leg muscle rigidity inability to walk respiratory distress because body temp increase heart failure

Question 35

PSS is caused by/ what goes wrong to cause PSS

Answer 35

a defect in gate of calcium releasing channel -prevents the channel from closing -calcium continues to leak into muscle -causes a high rate of metabolism to prolong acidosis and fatal collapse

Question 36

PSS leads to the production of

Answer 36

PSE (pale, soft, exudative meat)

Question 37

how to treat PSS

Answer 37

DNA test homozygous carriers and heterozygous should be culled

Question 38

examples of maternal traits

Answer 38

number born alive sow longevity embryo survival ovulation rate

Question 39

examples of terminal traits

Answer 39

meat quality backfat depth average daily gain flavor

Question 40

hermaphrodites are common in which breeds

Answer 40

landrace and Yorkshire