The Science of Maryland Agriculture · The Science of Maryland Agriculture University of Maryland Extension programs are open to all and will not discriminate against anyone because

The Science of Maryland Agriculture

University of Maryland Extension programs are open to all and will not discriminate against anyone because of race, age, sex, color, sexual orientation, physical or mental disability, religion, ancestry,

national origin, marital status, genetic information, political affiliation, or gender identity or expression.

GOAL STATEMENT: Students will learn how to predict plant and animal offspring traits or characteristics using genetics.

OBJECTIVES: • Students will apply the concepts of genotype and phenotype to scenarios involving agricultural

animals.• Students will utilize Punnett squares to make predictions about the genotype of phenotype of

offspring resulting from parent animals and will make breeding decisions based on these findings.

REQUIRED MATERIALS: • “Check Out Your Genetic Traits” worksheet (1 per student)• “Agricultural Animal Genetics” worksheet (1 per student)

AMOUNT OF TIME TO ALLOW: 60-90 minutes. Extension activities will take additional time.



Take a few seconds to look at everyone in the room. Chances are that no two people look exactly the same. In fact, it’s very likely that most people look very different from one another. This is because

almost every person in the world has their own unique set of genes that make them look the way they do. Identical twins are the only people who share the same exact genes with another person -

everyone else is completely unique!

Just like humans have genes, animals have genes, too. An animal’s genes determine many different things including coat color, height, whether or not they have horns, and so much more! Animal breeders have

to pay careful attention to genetics to make sure the animals they breed will create offspring with desired traits.

Some genes are dominant, meaning they mask the expression of other genes. Other genes are recessive and are only sometimes expressed in the offspring. Animal breeders need to have a solid understanding of genetics in order to make good decisions about which individuals to breed.

Following are some important vocabulary terms to understand when discussing parents and offspring in terms of animal breeding.

• Sire – male parent (father)• Dam – female parent (mother)• Cow – a female bovine• Bull – an intact male bovine• Calf – a young bovine• Mare – a female horse

• Stallion – an intact male horse• Foal – a young horse• Sow – a female pig• Boar – an intact male pig• Piglet – a young pig



Directions:1. Have students complete the vocabulary and Punnett square reviews on the “Agricultural Animal

Genetics” worksheet independently, then review the answers as a class. 2. Next, assign students into small groups, and assign a breeding scenario to each group. If the

class is large, you may wish to assign the same scenario to more than one group. 3. Allow groups several minutes to discuss their scenarios and to prepare a short explanation that

they will present to the class. 4. Have groups present and discuss each scenario as a class.

35 minutes

15 minutes

Have student groups share their breeding scenarios with the class and explain how they came to their conclusions. Reference the teacher’s guide of the worksheet included with this lesson for answers and explanations to each breeding scenario.

10 minutes

Note: Students should have previous knowledge of basic genetics, particularly the principles of inheritance and dominant/recessive traits.

Use the “Check Out Your Genetic Traits” worksheet as a warm up activity. Have students complete independently and then compare answers with a partner. After reviewing their responses, ask students

to raise their hands if they have the same color hair as one of their parents. Use this to lead into a review conversation about inheritance of traits. Then have students brainstorm genetic traits that can be

inherited in agricultural animals.

In Maryland, there are many plants and animals that are part of the agriculture industry. For example, did you know that there are over 87,000 horses in the state of Maryland? Horses come in a variety of sizes and coat colors. Coat colors include: black, chestnut, bay, gray, palomino, and sorrel (light brown) just to name a few. According to National Ag Statistics, Maryland has approximately 200,000 cows. They too come in a variety of colors. In addition, some have horns and some do not have horns (polled), both of which are genetic traits. Also, some cows have genes to produce large quantities of milk while others have been genetically selected to produce meat.

The lesson will explore how animal breeders use genetics to guide breeding decisions in order to produce animals with desired traits.



• Geneticist – This person conducts research to help scientists gain a better understanding of genetics such as how and why cells mutate or which traits can be passed from parent to offspring. Some geneticists work in the medical field to help people who have special genetic conditions.

• CropGeneticist – This person creates new crop varieties by cross breeding specific seeds, usually selecting for better traits like improved quality or increased yield.

• Animal Breeder – This person manages the breeding and reproduction of animals, usually selecting two parents that will produce offspring with better traits like higher milk production or faster muscle growth.

Horse breeders often want to produce offspring with specific coat colors, such as with the tobiano horse example in the lesson, and there are many colors and variations possible in terms of horse

coats. Breeders must have an understanding of the genetics governing color traits in order to produce foals with their desired coat color or pattern. Have students research different coat colors and patterns

and the genes that govern them and present their findings to the class. You may have students develop word problems like in the lesson and have other students complete the problems. Consult the following

resources to learn more about the genetics of horse coat colors.• “Basic Horse Genetics” from the Alabama Cooperative Extension System. Available at

<http://www.aces.edu/pubs/docs/A/ANR-1420/ANR-1420.pdf>• “Introduction to Coat Color Genetics” from the University of California-Davis Veterinary

Genetics Laboratory. Available at <http://www.vgl.ucdavis.edu/services/coatcolor.php> • “American Paint Horse Association’s Guide to Coat Color Genetics” from the American Paint

Horse Association. Available at <http://press.apha.com/pdfs/guidebooks/ColorGenGuide.pdf>• “Coat Color Calculator,” an interactive tool from Animal Genetics, Inc. Available at

<http://www.animalgenetics.us/ccalculator1.asp>

A pre/post test should be completed with this lesson plan. Student understanding of concepts can also be evaluated through class discussion as well as through evaluation of completed activity data sheets. Analysis/conclusion questions that are answered incorrectly by a large number of students should be addressed in a follow-up discussion.


University of Maryland Extension programs are open to all and will not discriminate against anyone because of race, age, sex, color, sexual orientation, physical or mental disability, religion, ancestry, national origin, marital status, genetic information, political affiliation, or gender identity or expression.

Name:

Date: Period:

Which of the following traits did you inherit from your parents? Check which trait best describes you.

1. Hair type

Curly

Straight

2. Little finger

Bent

Straight

3. Hair on the back of your fingers

No hair on fingers

Hair on the fingers

With a partner, check to see which of these traits best describes you.

4. Tongue rolling

Can roll tongue

Can’t roll tongue

5. Ear lobes

Unattached (A)

Attached (B)

6. Widow’s peak

Widow’s peak (A)

No widow’s peak (B)

A

A

B

B



Name:

Date: Period:

AgriculturalAnimalGenetics-VocabularyReview

A. The observable traits of an organism, such as coat color

B. One copy of a gene; an organism gets one from each parent

C. Is masked when two alleles differ; is expressed when two alleles are identical

D. When two alleles are identical

E. When two alleles are different

F. Is always expressed, whether the two alleles are identical or different

G. The genetic makeup of an organism

1. Dominant gene

2. Recessive gene

3. Allele

4. Phenotype

5. Genotype

6. Heterozygous

7. Homozygous

Match the terms below with the correct definitions.



Name:

Date: Period:

AgriculturalAnimalGenetics-PunnettSquareReviewA Punnett square is a simple way to predict the traits of offspring that will be produced when two specific individuals are mated. The genotype of one parent is listed down the side of the square, and the genotype of the other parent is listed across the top. The potential genotypes for offspring are written in the four boxes inside the square.

Scrapie is a fatal genetic disease that affects the nervous system of sheep. Scrapie is an infectious disease, but some animals are genetically immune. The scrapie gene (Q) is recessive to the scrapie-resistant gene (R). Complete the Punnett square below to determine the possible genotypes that could be produced by mating a ewe (female sheep) with genotype QR to a ram (male sheep) with genotype RR.

What percentage of the offspring from this mating will be scrapie-resistant?

Genotype of one parent

Genotype of other parent

B b

B

B

BB

BB

Bb

Bb



Name:

Date: Period:

AgriculturalAnimalGenetics-PollednessinCattleSome cattle have horns, and some don’t. Cattle that are born without horns are called polled. Polledness is a desirable trait because horns can be dangerous and make managing cattle more difficult. The polled gene (P) is dominant to the horned gene (p).

(Note that horns are different from antlers. Horns are present on animals like cattle and goats; males and females can have horns, and they are not shed. Antlers are present on animals like deer and moose; only males have antlers, and they are shed every year.)

State the phenotype and possible genotypes for the animals pictured below.

Phenotype:

Possible genotype(s):

You are a cattle breeder with a herd of polled cattle. Although you prefer polled cattle, you just inherited a new bull (male animal) that has horns. Complete the Punnett squares below to determine the percentage of offspring from your polled cows (females) that you can expect to be born with horns. (Hint: there are two Punnett squares because your polled cows may have two different possible genotypes. Assume your herd is made up of equal numbers of cows with each genotype.)

Phenotype:


Total percentage of offspring with horns:

Percentage with horns: Percentage with horns:

New bull New bull

Your cows



Name:

Date: Period:

AgriculturalAnimalGenetics-PollednessinCattle(2)

After breeding the horned bull this year, you will sell him and buy a different bull to breed next year. You have identified three potential bulls to buy.• Cheston is polled. Both his sire (father) and dam (mother) were also polled.• Wyeth has horns. His sire was polled, and his dam had horns.• Naylor is polled. His sire was polled, and his dam had horns.

You want to produce polled calves. Recall that your herd is made up of both polled and horned cows. Which bull is the best choice, and why?



Name:

Date: Period:

AgriculturalAnimalGenetics-TobianoCoatinHorsesTobiano is a coat marking pattern in horses in which the horse has broad white patches of hair over the entire body. Tobiano is a unique coat pattern, so people who breed tobiano horses prefer to produce foals with the tobiano marking. The tobiano gene (T) is dominant.

State whether each of the following horses will produce a tobiano foal if bred with a horse that is not tobiano.

Genotype: TT Genotype: Tt Genotype: tt

You are a horse breeder who raises Arabian horses. Arabians do not carry the tobiano gene, but you want to begin producing crossbred horses that have a tobiano coat pattern. You would like to buy a colt (young male horse) to breed to your solid-coated mares (female horses), and you have identified three potential choices.

• Merlin has a tobiano coat, and his dam (mother) has a solid coat.• Jasper has a solid coat, and his dam has a tobiano coat.• Tucker has a tobiano coat, and his dam has a tobiano coat.

First, determine the genotype of each of the three colts. (Hint: for one colt, there will be two possibilities.)• Merlin:

• Jasper:

• Tucker:

Next, use a Punnett Square to determine the likelihood that each of the three colts will produce a tobiano offspring when bred to a mare with a solid coat.



Name:

Date: Period:

You want to buy the colt with the highest likelihood of producing offspring with tobiano coats. Which colt is the best option?

AgriculturalAnimalGenetics-TobianoCoatinHorses(2)Merlin Jasper

Your mare

Tucker



Name:

Date: Period:

AgriculturalAnimalGenetics-PorcineStressSyndromeinPigsPorcine stress syndrome (PSS) is a genetic disorder in pigs that causes sudden death when pigs are exposed to stress. Meat from pigs with PSS is also negatively affected and can be either soft and watery or dark and dry. The gene for PSS is recessive (n).

State whether animals with each of the following genotypes will exhibit PSS. Circle the genotype of the animal who is a carrier.

You are a pig producer with ten sows (female pigs). You know that your sows do not carry any alleles for the PSS gene because you have had them all genetically tested for the disease. Last year you bred your sows to a Brutus, a neighbor’s boar (male pig). Once the piglets were mature, you decided to keep some as breeding animals and sent some to market.

Some of Brutus’s offspring that you sent to market produced pale, watery meat. What is the likelihood that this was caused by PSS?

You are concerned that Brutus may have been a carrier of PSS. You ask your neighbor to have Brutus genetically tested, but she has already sent him to market. Brutus’s meat appeared normal, but he may have been a carrier of PSS. Assuming Brutus was a carrier, complete the Punnett square to determine the percentage of his offspring with your sows that could be carriers of PSS.

NN Nn nn

Your sows

Brutus

Percent of Brutus’s offspring that may be carriers of PSS:



Name:

Date: Period:

Your sows produced 80 piglets as a result of breeding with Brutus. Because you are expanding your pig breeding operation, you sent half of the offspring to market and kept the other half as breeding animals.

However, you do not want to breed any pigs that carry the PSS gene. You could have all your breeding animals tested, but the genetic test is expensive.

What is the least number of Brutus’s offspring that you must have genetically tested in order to determine whether he was a carrier? Explain your answer.

AgriculturalAnimalGenetics-PorcineStressSyndromeinPigs(2)



TEACHERKEY:AgriculturalAnimalGenetics-VocabularyReview

A. The observable traits of an organism, such as coat color

B. One copy of a gene; an organism gets one from each parent

C. Is masked when two alleles differ; is expressed when two alleles are identical

D. When two alleles are identical

E. When two alleles are different

F. Is always expressed, whether the two alleles are identical or different

G. The genetic makeup of an organism

1. Dominant gene

2. Recessive gene

3. Allele

4. Phenotype

5. Genotype

6. Heterozygous

7. Homozygous

Match the terms below with the correct definitions.

F

C

B

A

G

E

D



TEACHERKEY:AgriculturalAnimalGenetics-PunnettSquareReview

Genotype of one parent

Genotype of other parent

B b

B

B

BB

BB

Bb

Bb

A Punnett square is a simple way to predict the traits of offspring that will be produced when two specific individuals are mated. The genotype of one parent is listed down the side of the square, and the genotype of the other parent is listed across the top. The potential genotypes for offspring are written in the four boxes inside the square.

Scrapie is a fatal genetic disease that affects the nervous system of sheep. Scrapie is an infectious disease, but some animals are genetically immune. The scrapie gene (Q) is recessive to the scrapie-resistant gene (R). Complete the Punnett square below to determine the possible genotypes that could be produced by mating a ewe (female sheep) with genotype QR to a ram (male sheep) with genotype RR.

What percentage of the offspring from this mating will be scrapie-resistant?

Q R

R

R

QR

QR

RR

RR

100%



TEACHERKEY:AgriculturalAnimalGenetics-PollednessinCattleSome cattle have horns, and some don’t. Cattle that are born without horns are called polled. Polledness is a desirable trait because horns can be dangerous and make managing cattle more difficult. The polled gene (P) is dominant to the horned gene (p).

(Note that horns are different from antlers. Horns are present on animals like cattle and goats; males and females can have horns, and they are not shed. Antlers are present on animals like deer and moose; only males have antlers, and they are shed every year.)

State the phenotype and possible genotypes for the animals pictured below.

Phenotype:


You are a cattle breeder with a herd of polled cattle. Although you prefer polled cattle, you just inherited a new bull (male animal) that has horns. Complete the Punnett squares below to determine the percentage of offspring from your polled cows (females) that you can expect to be born with horns. (Hint: there are two Punnett squares because your polled cows may have two different possible genotypes. Assume your herd is made up of equal numbers of cows with each genotype.)

Phenotype:


Total percentage of offspring with horns:

Percentage with horns: Percentage with horns:

New bull New bull

Your cows

polled horned or not polled

PP or Pp pp

p p p p

P

P

P

P

Pp Pp

Pp Pp

Pp Pp

pp pp

0% 50%

25%



TEACHERKEY:AgriculturalAnimalGenetics-PollednessinCattle(2)

After breeding the horned bull this year, you will sell him and buy a different bull to breed next year. You have identified three potential bulls to buy.• Cheston is polled. Both his sire (father) and dam (mother) were also polled.• Wyeth has horns. His sire was polled, and his dam had horns.• Naylor is polled. His sire was polled, and his dam had horns.

You want to produce polled calves. Recall that your herd is made up of both polled and horned cows. Which bull is the best choice, and why?Cheston is the best choice. Because both of his parents were polled, there is a chance that he is

homozygous for the polled gene; Cheston’s genotype is either PP or Pp. Naylor, however, cannot

be homozygous for the polled gene because his mother had horns and did not carry the polled

gene (pp); Naylor’s genotype is Pp. Thus Cheston has a higher probability of producing polled

calves. Wyeth is not a good choice because he has horns, meaning he does not carry the polled

gene. Wyeth will only produce polled calves when bred to polled cows.



TEACHERKEY:AgriculturalAnimalGenetics-TobianoCoatinHorsesTobiano is a coat marking pattern in horses in which the horse has broad white patches of hair over the entire body. Tobiano is a unique coat pattern, so people who breed tobiano horses prefer to produce foals with the tobiano marking. The tobiano gene (T) is dominant.

State whether each of the following horses will produce a tobiano foal if bred with a horse that is not tobiano.

Genotype: TT Genotype: Tt Genotype: tt

You are a horse breeder who raises Arabian horses. Arabians do not carry the tobiano gene, but you want to begin producing crossbred horses that have a tobiano coat pattern. You would like to buy a colt (young male horse) to breed to your solid-coated mares (female horses), and you have identified three potential choices.

• Merlin has a tobiano coat, and his dam (mother) has a solid coat.• Jasper has a solid coat, and his dam has a tobiano coat.• Tucker has a tobiano coat, and his dam has a tobiano coat.

First, determine the genotype of each of the three colts. (Hint: for one colt, there will be two possibilities.)• Merlin:

• Jasper:

• Tucker:

Next, use a Punnett Square to determine the likelihood that each of the three colts will produce a tobiano offspring when bred to a mare with a solid coat.

YES YES NO

Tt

tt

TT or Tt



You want to buy the colt with the highest likelihood of producing offspring with tobiano coats. Which colt is the best option?

TEACHERKEY:AgriculturalAnimalGenetics-TobianoCoatinHorses(2)Merlin Jasper

Your mare

TuckerT t

t

t

Tt tt

Tt tt

t t

t

t

tt tt

tt tt

T T (or t)

t

t

Tt Tt

Tt Tt

Tucker is the best option. We do not know Tucker’s genotype for certain; he could be either Tt or

TT. We do know Merlin’s and Jasper’s genotypes for certain. If Tucker is Tt, he has a 50% chance

of producing a tobiano offspring. Merlin has the same chance. However, it Tucker is TT, he has a

100% chance of producing tobiano offspring.



TEACHERKEY:AgriculturalAnimalGenetics-PorcineStressSyndromeinPigsPorcine stress syndrome (PSS) is a genetic disorder in pigs that causes sudden death when pigs are exposed to stress. Meat from pigs with PSS is also negatively affected and can be either soft and watery or dark and dry. The gene for PSS is recessive (n).

State whether animals with each of the following genotypes will exhibit PSS. Circle the genotype of the animal who is a carrier.

You are a pig producer with ten sows (female pigs). You know that your sows do not carry any alleles for the PSS gene because you have had them all genetically tested for the disease. Last year you bred your sows to a Brutus, a neighbor’s boar (male pig). Once the piglets were mature, you decided to keep some as breeding animals and sent some to market.

Some of Brutus’s offspring that you sent to market produced pale, watery meat. What is the likelihood that this was caused by PSS?

You are concerned that Brutus may have been a carrier of PSS. You ask your neighbor to have Brutus genetically tested, but she has already sent him to market. Brutus’s meat appeared normal, but he may have been a carrier of PSS. Assuming Brutus was a carrier, complete the Punnett square to determine the percentage of his offspring with your sows that could be carriers of PSS.

NN Nn nn

Your sows

Brutus

Percent of Brutus’s offspring that may be carriers of PSS:

no no yes

The soft, watery meat was not a result of PSS. Genetic testing confirmed that all of your sows

were genotype NN so they do not exhibit or carry the gene for PSS. If Brutus carried the PSS

gene, the offspring could be carriers of PSS but would not exhibit symptoms.

N N

N

n

NN NN

Nn Nn 50%



Your sows produced 80 piglets as a result of breeding with Brutus. Because you are expanding your pig breeding operation, you sent half of the offspring to market and kept the other half as breeding animals.

However, you do not want to breed any pigs that carry the PSS gene. You could have all your breeding animals tested, but the genetic test is expensive.

What is the least number of Brutus’s offspring that you must have genetically tested in order to determine whether he was a carrier? Explain your answer.

TEACHERKEY:AgriculturalAnimalGenetics-PorcineStressSyndromeinPigs(2)

You only need to have one positive result to know that Brutus was a carrier, but you can’t be

sure he wasn’t a carrier unless you test Brutus himself. Theoretically only 50% of the offspring

would be carriers and 50% would not be carriers, but in real life this may not be the result seen.

The more negative results you see, the greater the likelihood that he was not a carrier.



PRE-Evaluation:What’sInYourGenes?1. How old are you? ______________

3. Are you….(Select ALL that apply.) African American/Black Asian Other Native American/Alaskan Native Hispanic/Latino White Native Hawaiian/Other Pacific Islander

4. What type of school do you go to? (Select one.) Public school Private school Religious school (Catholic, etc.) Home school

2. Are you... (Select one.) A boy A girl

YourScienceandAgricultureOpinionsandKnowledge5. BEFOREgoingthroughtheAGsplorationProgram, please circle the degree to which you agree or disagree with the following statements.

6. BEFOREgoingthroughtheAGsplorationProgram, please circle your knowledge level about the topics listed below.

StronglyDisagree Disagree Agree Strongly

Agree

I like science. 1 2 3 4

I feel that Maryland agriculture is a part of science. 1 2 3 4

Science is useful for solving everyday problems. 1 2 3 4

Maryland agriculture is beneficial to me, my family, and my community.

1 2 3 4

When I graduate from high school, I would like to have a job in agricultural science.

1 2 3 4

I can name three jobs in the agriculture industry. 1 2 3 4

None Low Medium High VeryHigh

Maryland agriculture 1 2 3 4 5

Heredity 1 2 3 4 5

Chromosomes 1 2 3 4 5

Phenotype 1 2 3 4 5

Genotype 1 2 3 4 5

Dominant genes 1 2 3 4 5

Recessive genes 1 2 3 4 5



POST-Evaluation:What’sinYourGenes?YourScienceandAgricultureOpinionsandKnowledge7. AFTERgoingthroughtheAGsplorationProgram, please circle the degree to which you agree or disagree with the following statements.

8. AFTERgoingthroughtheAGsplorationProgram, please circle your knowledge level about the topics listed below.

9. As a result of participating in this activity, tell one new thing you will try or one thing you will find information about.

StronglyDisagree Disagree Agree Strongly

Agree

I like science. 1 2 3 4

I feel that Maryland agriculture is a part of science. 1 2 3 4

Science is useful for solving everyday problems. 1 2 3 4

Maryland agriculture is beneficial to me, my family, and my community.

1 2 3 4

When I graduate from high school, I would like to have a job in agricultural science.

1 2 3 4

I can name three jobs in the agriculture industry. 1 2 3 4



Heredity 1 2 3 4 5


Phenotype 1 2 3 4 5

Genotype 1 2 3 4 5





SUPPLEMENTAL-Evaluation:What’sInYourGenes?Directions: If you are teaching more than one lesson plan in one day, you may attach this to the pre/post evaluation form for the other lesson you are teaching. Please have the student fill out these during the pre and post evaluation times. In addition, only have the student fill out the post evaluation questions Q5 – Q7 at the completion of all lessons.

PRE-EvaluationBEFORE going through the AGsploration Program, please circle your knowledge level about the topics listed below.

POST-EvaluationAFTER going through the AGsploration Program, please circle your knowledge level about the topics listed below.



Heredity 1 2 3 4 5


Phenotype 1 2 3 4 5

Genotype 1 2 3 4 5





Heredity 1 2 3 4 5


Phenotype 1 2 3 4 5

Genotype 1 2 3 4 5



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The Science of Maryland Agriculture · The Science of Maryland Agriculture University of Maryland Extension programs are open to all and will not discriminate against anyone because