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Genes Genes

Genes - PowerPoint Presentation

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Uploaded On 2015-11-15

Genes - PPT Presentation

Located on chromosomes Thousands found in each animal Control inherited characteristics Carcass traits Growth rate Feed efficiency Two types of inherited traits Dominant Recessive Genes Dominant gene ID: 194878

cross polled black red polled cross red black cow gene trait bull dihybrid bbpp horned homozygous heritability recessive dominant

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Presentation Transcript

Slide1

Genes

Located on chromosomes

Thousands found in each animal

Control inherited characteristics

Carcass traits

Growth rate

Feed efficiency

Two types of inherited traits

Dominant

Recessive Slide2

Genes

Dominant gene

Hides

the effect of another gene

Polled condition in cattle is dominant

The gene is represented by a capital letter

Recessive

Gene

that is hidden by another

The gene is represented by a lower case letterSlide3

Genes

Example:

The dominant gene is written-

P

The recessive gene is written-

p

P

= Polled

p

= hornedSlide4

Homozygous and Heterozygous

Homozygous gene pair

Carries two genes for a trait

Polled cow might carry the gene PP

Heterozygous (or hybrid)

Carries two different genes that affect a trait

Polled cows might carry a recessive gene with the dominant PpSlide5

Punnett Square

P

= Polled

p

= horned

Example:

Two polled cattle that are homozygous for the polled trait

P

P

P

PPPPPPPPP

Polled Dam

Polled SireSlide6

Punnett Square

N= Normal size

n= Dwarfism

Example:

Normal size in cattle is dominant to dwarfism

N

N

N

NN

NN

nNnNn

Normal Dam

Sire CarrierSlide7

Punnett Square

N= Normal size

n= Dwarfism

Example:

What if both parents are carriers for a trait or disorder?

N

n

N

NN

Nn

nNnnn

Normal Dam

Sire Carrier

Result

: one out of every four births could result in a dwarf animal (1:2:1)Slide8

Monohybrid Cross

A monohybrid cross is an estimation of a predicted outcome for a single trait.

If a homozygous horned cow (pp) is bred with a heterozygous polled bull (Pp), what percent of the calves will be polled

?Slide9

Dihybrid Cross

A

dihybrid

cross is a estimation of a predicted outcome for two traits.

What

results if an Angus bull that is homozygous black and polled (BBPP) is bred with a red shorthorn cow which is homozygous red and horned (

bbpp

).

The bull BBPP can be simplified to BP (black & polled is the only possible contribution for the bull).

The cow

bbpp can be simplified to bp (red & horned is the only possible contribution for the cow).Slide10

Dihybrid Cross

Black = 100%

Polled = 100%

Horned = 0%Slide11

Dihybrid Cross

Now if two of the offspring which are heterozygous for black/red and polled/horned (BbPp) are mated.

How do you do a Punnett square for two heterozyous animals?

Use all possible gene combinations.

Both the bull and cow are BbPp.

What are the possible contributions?

BP, Bp, bP, bp for both animals. (4 x 4 grid)Slide12

Dihybrid CrossSlide13

Dihybrid Cross

Black Polled = 9 out of 16 or 56.25%

Black Horned = 3 out of 16 or 18.75%

Red Polled = 3 out of 16 or 18.75%

Red Horned = 1 out of 16 or 6.25%Slide14

Dihybrid Cross

If a heterozygous bull (BbPp) is mated to a homozygous cow (BBPP).

What are the outcomes?Slide15

Dihybrid CrossSlide16

Dihybrid Cross

If a (BbPp) bull is mated to a (BBPp) cow.

what are the outcomes?Slide17

Dihybrid CrossSlide18

Assignment

Complete a Punnett Square for two animals that are heterozygous for two traits:

Polled=P

Black= B

(Alternatives are horned and red)

Dam

SireSlide19

Practice

Black

is dominant (B), and red is recessive (b).

"

Predict the offspring from the cross of a red bull and a black cow if the black cow's mother was red

".Slide20

First things first: the only way for the red bull to be red (the recessive trait) is if it's genotype is homozygous recessive (2 little letters), so the red bull is "bb". Now, the black cow's genotype could be either "BB" or "Bb". If its mommy was red (bb), then this black cow MUST have inherited a little "b" from its mommy. So the black one in our cross is "Bb" (not "BB"), and our cattle cross is: Bb x bb. Slide21

Heritability

Objective:

Discuss hertability estimates for beef and swineSlide22

Heritability

Estimated the likelihood of a trait being passes on from the parent to the offspring

Low heritability

slow herd improvement

High heritability

faster improvementSlide23

Heritability

Swine rates are usually lower than cattle

Heritiability for carcass traits are higher than reproductive traits

Estimates vary from 0 to 70%Slide24

Heritability

Estimates - cattle

Trait % Heritable

Number Born 5

Weaning Wight 30

Yeild

Grade 30

Carcass Grade 35

Yearling Weight 40

Scrotal Circumference 50

Retail Yeild 60Rib Eye Area 70Slide25

Heritability

Estimates - Swine

Trait % Heritable

Litter Size 10

Weaning Wight (3

wks

) 15

Birth Weight 20

Feed Efficiency 30

Carcass length 50Slide26

Heritability

Estimates - Sheep

Trait % Heritable

Number Born 13

Weaning Wight 30

Birth Weight 30

Feed Efficiency 20

Carcass (percent lean) 35