Experiment Summary Statements 1) The mutagen applied to the truebreeding seed induced phenotype variations in the soybeans. 2)The mutagen induced mutations

Experiment Summary StatementsExperiment Summary Statements

1) The mutagen applied to the truebreeding seed induced1) The mutagen applied to the truebreeding seed inducedphenotype variations in the soybeans. phenotype variations in the soybeans.

2)The mutagen induced mutations (changes) in the genetic2)The mutagen induced mutations (changes) in the geneticmakeup of the plant which were passed on to offspring,makeup of the plant which were passed on to offspring,and thus the unique phenotypes were inherited.and thus the unique phenotypes were inherited.

3)The genetic makeup of the M2 plants was not always the 3)The genetic makeup of the M2 plants was not always the same. Some were homozygous, others heterozygous.same. Some were homozygous, others heterozygous.

4) The mutations were random. Dr. Specht did not observe4) The mutations were random. Dr. Specht did not observethe indeterminate mutant he was hoping for, but observedthe indeterminate mutant he was hoping for, but observedmany other random mutations instead.many other random mutations instead.

What is a Monohybrid Cross?What is a Monohybrid Cross?

A monohybrid cross is a cross between two plants that differ A monohybrid cross is a cross between two plants that differ by a single trait (mono). Monohybrid crosses are done to allow by a single trait (mono). Monohybrid crosses are done to allow plant breeders to follow the inheritance of the single trait more plant breeders to follow the inheritance of the single trait more easily.easily.

Monohybrid crosses were used on theMonohybrid crosses were used on thedwarf and soybean lesion mutants todwarf and soybean lesion mutants to

learn about the inheritance of theselearn about the inheritance of thesemutant traits.mutant traits.

Dwarf MutantDwarf MutantSoybeanSoybean

Lesion MutantLesion MutantSoybeanSoybean

What is a reciprocal cross?What is a reciprocal cross?

A cross is made between plants withA cross is made between plants withtwo different phenotypes using onetwo different phenotypes using one

phenotype as the male and the otherphenotype as the male and the otherphenotype as the female.phenotype as the female.

In a reciprocal cross, a second crossIn a reciprocal cross, a second crossis made switching theis made switching the

phenotypes of the male andphenotypes of the male andfemale.female.

XX

Reciprocal CrossReciprocal Cross

XX

M3 plants homozygous for the M3 plants homozygous for the dwarf mutantdwarf mutant traits were crossed to traits were crossed tohomozygous normal plants and the F1 seed harvested and bagged.homozygous normal plants and the F1 seed harvested and bagged.

DDDDdddd DDDD dddd

PollenPollendonordonor


Cross 1: Cross 1: Pollen donor = Pollen donor = MutantMutant

Cross 2: Cross 2: Pollen donor = Pollen donor = NormalNormal

XX

Crosses were also made for Crosses were also made for soybean lesion mutantssoybean lesion mutants..

GGGGgggg GGGG gggg



Cross 1: Cross 1: Pollen donor = Pollen donor = MutantMutant

Cross 2: Cross 2: Pollen donor = Pollen donor = NormalNormal

XX

Reciprocal CrossReciprocal Cross

Why do a reciprocal cross?Why do a reciprocal cross?

Sometimes traits are passed on onlySometimes traits are passed on onlymaternally (through the female) ormaternally (through the female) or

paternally (throught the male).paternally (throught the male).

If this is true for a particular trait,If this is true for a particular trait,the offspring of the two crosses in athe offspring of the two crosses in areciprocal cross will have differentreciprocal cross will have different

phenotypes. phenotypes.

This allows plant breeders to determine if This allows plant breeders to determine if aa

trait is passed on in this way.trait is passed on in this way.

Making a CrossMaking a CrossStamen and Pollen =Stamen and Pollen =

male partmale part

Stigma and style =Stigma and style =female partfemale part

Making a CrossMaking a CrossSoybeans are self-pollinating.Soybeans are self-pollinating.

Therefore, cross pollination must be done manually.Therefore, cross pollination must be done manually.

View soybean crossing videoView soybean crossing video

Making a CrossMaking a Cross

The anthers are removed from female flowerThe anthers are removed from female flowerto prevent self pollination.to prevent self pollination.

Making a CrossMaking a Cross

Pollen taken from anther of another flower andPollen taken from anther of another flower anddusted onto stigma of female flower.dusted onto stigma of female flower.

Soybean flowersSoybean flowers

Soybean antherSoybean anther

Soybean flowersSoybean flowers

Cross pollinatedCross pollinated

flowers are labeled.flowers are labeled.

Pods will formPods will formcontaining seedcontaining seedfrom the cross.from the cross.

Dwarf Cross - F1 SeedDwarf Cross - F1 Seed

The F1 seed was plantedThe F1 seed was plantedkeeping the reciprocal crosskeeping the reciprocal cross

seed in a separate plot.seed in a separate plot.

PlantPlantSeedSeed

PlantPlantSeedSeed

Pollen donor = Pollen donor = MutantMutant Pollen donor = Pollen donor = NormalNormal

Dwarf Cross - F1 PlantsDwarf Cross - F1 Plants

The F1 plant phenotypes wereThe F1 plant phenotypes wereobserved, and the plants allowed to self-pollinateobserved, and the plants allowed to self-pollinate

to produce F2 seed.to produce F2 seed.


All of the F2 seed was harvestedAll of the F2 seed was harvestedwith seeds from each individual plantwith seeds from each individual plant

placed in a separate labeled envelope.placed in a separate labeled envelope.


Dwarf Cross - F1 PlantsDwarf Cross - F1 Plants

The F2 seed was planted in progeny rows.The F2 seed was planted in progeny rows.Again the reciprocal cross seed wasAgain the reciprocal cross seed was

planted in a separate plot.planted in a separate plot.


Dwarf Cross – F2 SeedDwarf Cross – F2 Seed

The F2 plant phenotypes were observedThe F2 plant phenotypes were observedand recorded, and the plants allowed to self-pollinateand recorded, and the plants allowed to self-pollinate

to produce F3 seed.to produce F3 seed.


Dwarf Cross – F2 PlantsDwarf Cross – F2 Plants

All of the F3 seed was harvested from each plant andAll of the F3 seed was harvested from each plant andplaced in separate envelopes labeled with the phenotypeplaced in separate envelopes labeled with the phenotype

of the parent plant (Dwarf or Normal).of the parent plant (Dwarf or Normal).

NormalNormal

DWARFDWARF

DWARFDWARF

DWARFDWARF


Dwarf Cross – F2 PlantsDwarf Cross – F2 Plants

DWARFDWARFNormalNormalNormalNormal DWARFDWARF

NormalNormalNormalNormal


DWARFDWARFDWARFDWARF

NormalNormal NormalNormalNormalNormalNormalNormal

The F3 seed was planted in progeny rows.The F3 seed was planted in progeny rows.The reciprocal cross seed was planted in the same plot.The reciprocal cross seed was planted in the same plot.

The F3 seed was planted in progeny rows.The F3 seed was planted in progeny rows.


DWARFDWARFNormalNormal

NormalNormalDWARFDWARFNormalNormalNormalNormal

DWARFDWARFDWARFDWARFNormalNormalNormalNormalNormalNormalNormalNormal

Soybean Disease Lesion MutantSoybean Disease Lesion Mutant

At the same time, these steps were takenAt the same time, these steps were takenwith the soybean disease lesion mutants.with the soybean disease lesion mutants.

Lesion Mutant SoybeanLesion Mutant Soybean

Normal X Mutant Individual Plants Row Type

Normal Mutantall

normal row

mixed row

F1 plants 5 0F2 plants 18 6F3 rows from normal F2s ----- ----- 8 10F3 plants from mixed rows 172 46

Mutant X Normal Individual Plants Row Type

Normal Mutantall

normal row

mixed row

F1 plants 6 0F2 plants 81 27F3 rows from normal F2s ----- ----- 29 52F3 plants from mixed rows 178 49

Soybean Disease Lesion Mutant DataSoybean Disease Lesion Mutant Data

Summary of ResultsSummary of Results

1)1) All F1 plants had the normal phenotypeAll F1 plants had the normal phenotype

2)2) In both the first cross and reciprocal cross,In both the first cross and reciprocal cross, - Mutant phenotype not apparent in F1’s- Mutant phenotype not apparent in F1’s

- Mutant phenotype did reappear in F2’s- Mutant phenotype did reappear in F2’s - About ¼ of F2 plants had mutant- About ¼ of F2 plants had mutant

phenotype of dwarf or disease lesion.phenotype of dwarf or disease lesion.

Normal Mutant Ratio

F1 Plants 11 0 1:0

Normal Mutant Ratio

F2 Plants 99 33 3:1


3) Two types of plants had3) Two types of plants had the normal phenotypethe normal phenotype in the F2. About 1/3 ofin the F2. About 1/3 of the F2 normals werethe F2 normals were trubreeding while 2/3 trubreeding while 2/3

had mixed progeny had mixed progeny rows.rows.

4) Mutant F2 plants were4) Mutant F2 plants were truebreeding and all oftruebreeding and all of their F3 progeny weretheir F3 progeny were mutants.mutants.

F3 rows = 1:2:1F3 rows = 1:2:1F2F2

Explaining the Results Using theExplaining the Results Using thePrinciple of SegregationPrinciple of Segregation

1)1) The variation in the dwarf and lesion traits was controlledThe variation in the dwarf and lesion traits was controlled by genes. Genes store the information that controls theby genes. Genes store the information that controls the expression of traits. Alternative versions of genes calledexpression of traits. Alternative versions of genes called alleles allow for the expression of different traits.alleles allow for the expression of different traits.

2)2) Genes are found in pairs in somatic cells that make upGenes are found in pairs in somatic cells that make up the plant.the plant.

3)3) Paired genes separate during gamete formation and onePaired genes separate during gamete formation and one gene from each pair goes into a gamete.gene from each pair goes into a gamete.

4)4) Gametes fuse at random during sexual reproductionGametes fuse at random during sexual reproduction producing the next generation seed.producing the next generation seed.


Dr. Specht now had to use the data to figure outDr. Specht now had to use the data to figure outwhat was happening on the gene level.what was happening on the gene level.

We will use the data to answer someWe will use the data to answer somequestions and see if we can arrive at thequestions and see if we can arrive at the

same conclusions he did.same conclusions he did.


The Principle of Segregation explains whatThe Principle of Segregation explains whatDr. Specht observed with his plants in the field.Dr. Specht observed with his plants in the field.

He can test the validity of the principleHe can test the validity of the principlein explaining his results.in explaining his results.

We will use the data to answer someWe will use the data to answer somequestions and see if we can arrive at thequestions and see if we can arrive at the

same conclusions he did.same conclusions he did.

QUESTION?QUESTION?

Looking at the data for the Looking at the data for the soybeansoybeanlesion mutantlesion mutant, which trait was dominant?, which trait was dominant?

Normal traitNormal trait

Soybean lesion mutant traitSoybean lesion mutant trait

ANSWERANSWER

Since there are only normal and no lesionSince there are only normal and no lesion

phenotypes in the F1, it can be assumedphenotypes in the F1, it can be assumed

normal is dominant and masked thenormal is dominant and masked the

expression of the mutant trait (recessive). expression of the mutant trait (recessive).

The normal trait is dominant.The normal trait is dominant.

Normal Mutant Ratio

F1 Plants 11 0 1:0

QUESTION?QUESTION?

AA AA XX Aa Aa

aa aa XX Aa Aa

What are the genotypes of the originalWhat are the genotypes of the originalparents for the soybean lesion trait? parents for the soybean lesion trait?

Use Use ‘A’‘A’ to represent the dominant allele and to represent the dominant allele and‘‘a’a’ to represent the recessive allele. to represent the recessive allele.

AA AA XX aa aa

ANSWERANSWER

The genotype of one parent is The genotype of one parent is ‘AA’‘AA’ and other parent is and other parent is ‘aa’‘aa’..

The experiment states that a cross was madeThe experiment states that a cross was madebetween a truebreeding normal plant and abetween a truebreeding normal plant and atruebreeding soybean lesion mutant plant.truebreeding soybean lesion mutant plant.

Truebreeding means both parents are homozygousTruebreeding means both parents are homozygousfor the trait. for the trait.

Therefore, neither parent could be genotype Therefore, neither parent could be genotype ‘Aa’‘Aa’. . We have determined that normal is dominant. We have determined that normal is dominant.

Therefore its genotype would be Therefore its genotype would be ‘AA’‘AA’..That means the lesion-type is recessive, genotype That means the lesion-type is recessive, genotype ‘aa’‘aa’..

The original cross was: The original cross was: AA x aaAA x aa

QUESTION?QUESTION?

AA AA

AaAa

What is(are) the genotype(s) of theWhat is(are) the genotype(s) of theF1 generation for the soybean lesion trait? F1 generation for the soybean lesion trait?

Use Use ‘A’‘A’ to represent the dominant allele and to represent the dominant allele and‘‘a’a’ to represent the recessive allele. to represent the recessive allele.

aaaa

AA, Aa, & aaAA, Aa, & aa

ANSWERANSWER

The genotype of all the F1 offspringThe genotype of all the F1 offspringis is ‘Aa’‘Aa’

Aa

(Normal)

Aa

(Normal)

Aa

(Normal)

Aa

(Normal)

Normal parentNormal parent

allelesalleles

Lesi

on p

aren

tLe

sion

par

ent

a lle

les

a lle

l es

AA AA

aa

aa

The The ‘AA’‘AA’ parent can parent can

contribute only gametescontribute only gametes

with with ‘A’‘A’ alleles. alleles.

The The ‘aa’‘aa’ parent can parent can

contribute only gametescontribute only gametes

with with ‘a’‘a’ alleles. alleles.

Therefore, the F1 progeny Therefore, the F1 progeny will all have will all have ‘Aa’‘Aa’ genotypes. genotypes.

QUESTION?QUESTION?

1 AA : 2 Aa : 1 aa1 AA : 2 Aa : 1 aa

What is(are) the genotype(s) of theWhat is(are) the genotype(s) of theF2F2 generation for the soybean lesion trait generation for the soybean lesion trait

And in what ratios do they appear? And in what ratios do they appear? Use Use ‘A’‘A’ to represent the dominant allele and to represent the dominant allele and

‘‘a’a’ to represent the recessive allele. to represent the recessive allele.

1 AA : 1 Aa : 1 aa1 AA : 1 Aa : 1 aa 1 AA : 1 aa1 AA : 1 aa

1 Aa1 Aa

ANSWERANSWER

The genotypes and ratios of the F2The genotypes and ratios of the F2offspring are offspring are 1 AA : 2 Aa : 1 aa1 AA : 2 Aa : 1 aa

Normal F1 Normal F1 parent allelesparent alleles

Nor

mal

F1

Nor

mal

F1

par e

n t a

l lele

spa

rent

al le

les

AA aa

AA

aa

Since the F1 plant (Aa) is Since the F1 plant (Aa) is “selfed”, each parent contributes “selfed”, each parent contributes both an ‘A’ and ‘a’ allele.both an ‘A’ and ‘a’ allele.

The gametes for theThe gametes for thePunnett square would bePunnett square would be50% ‘A’ and 50% ‘a’.50% ‘A’ and 50% ‘a’.

F2 genotypic ratios areF2 genotypic ratios are

1 AA : 2 Aa : 1 aa1 AA : 2 Aa : 1 aa

AA

Aa

Aa

aa

QUESTION?QUESTION?

2 Normal : 1 Lesion2 Normal : 1 Lesion

What are the phenotypes of theWhat are the phenotypes of theF2F2 generation for the soybean lesion trait generation for the soybean lesion trait

And in what ratios do they appear? And in what ratios do they appear?



ANSWERANSWER

The phenotypes and ratios of the F2The phenotypes and ratios of the F2offspring are offspring are 3 Normal : 1 Lesion.3 Normal : 1 Lesion.


Nor

mal

F1

Nor

mal

F1

par e

n t a

l lele

spa

rent

al le

les AA aa

AA

aa

The The ‘A’‘A’ allele, which codes for allele, which codes for the normal trait, is dominant. the normal trait, is dominant. Therefore, the only way toTherefore, the only way toget the lesion phenotypeget the lesion phenotypeis with the ‘aa’ genotype.is with the ‘aa’ genotype.

The ¼ ‘AA’ offspring andThe ¼ ‘AA’ offspring andthe ½ ‘Aa’ offspring willthe ½ ‘Aa’ offspring willboth have the normalboth have the normalphenotype.phenotype.

AA

(Normal)

Aa

(Normal)

Aa

(Normal)

aa

(Lesion)

QUESTION?QUESTION?

1 AA : 2 Aa1 AA : 2 Aa

Of the Of the F2F2 generation progeny with a generation progeny with anormalnormal phenotype, what is the ratio of phenotype, what is the ratio ofhomozygous to heterozygoushomozygous to heterozygous plantsplants

for the soybean lesion trait?for the soybean lesion trait?

1 AA : 1 Aa1 AA : 1 Aa

1 AA : 3 Aa1 AA : 3 Aa

ANSWERANSWER

The ratio of homozygous to heterozygous F2 normalThe ratio of homozygous to heterozygous F2 normalplants is plants is 1 Homozygous : 2 Heterozygous.1 Homozygous : 2 Heterozygous.


Nor

mal

F1

Nor

mal

F1

par e

n t a

l lele

spa

rent

al le

les AA aa

AA

aa

We do not even look at the We do not even look at the lesion offspring when figuringlesion offspring when figuringthis ratio.this ratio.

Of the 3 normal offspring,Of the 3 normal offspring,1 has the 1 has the ‘AA’‘AA’ genotype genotype(homozygous).(homozygous).And 2 have the And 2 have the ‘Aa’‘Aa’genotype (heterozygous).genotype (heterozygous).

AA

(Normal)

Aa

(Normal)

Aa

(Normal)

aa

(Lesion)

*BONUS QUESTION?**BONUS QUESTION?*

Self pollinate the plants and plant them inSelf pollinate the plants and plant them inprogeny rows to observe the offspring.progeny rows to observe the offspring.

If you were a plant breeder, whatIf you were a plant breeder, whatexperiment might you perform to determineexperiment might you perform to determinewhich of the F2 normal phenotype plantswhich of the F2 normal phenotype plants

were homozygous and which werewere homozygous and which wereheterozygous?heterozygous?

Cross pollinate the plants and plant themCross pollinate the plants and plant themin progeny rows to observe the offspring.in progeny rows to observe the offspring.

ANSWERANSWER

Self pollinating the plants would give the results Self pollinating the plants would give the results below. If lesion plants were observed in the progeny below. If lesion plants were observed in the progeny rows, you could determine that the selfed parent had rows, you could determine that the selfed parent had

to pass on an to pass on an ‘a’‘a’ allele and was heterozygous. allele and was heterozygous.AA aa

AA

aa

AA

(Normal)

Aa

(Normal)

Aa

(Normal)

aa

(Lesion)

Self pollinate the plants and plant them inSelf pollinate the plants and plant them inprogeny rows to observe the offspring.progeny rows to observe the offspring.

AA AA

AA

AA

AA

(Normal)

AA

(Normal)

AA

(Normal)

AA

(Normal)

SummarySummary

A monohybrid cross is used to study the inheritanceA monohybrid cross is used to study the inheritanceof a single gene.of a single gene.

A reciprocal cross is used to determine if theA reciprocal cross is used to determine if thetrait is sex-linked.trait is sex-linked.

Soybeans must be cross-pollinated by hand.Soybeans must be cross-pollinated by hand.

The results of the soybean lesion cross indicate thatThe results of the soybean lesion cross indicate thatthe trait is recessive.the trait is recessive.

The results observed in progeny of the experimentThe results observed in progeny of the experimentfollow the Principle of Segregation.follow the Principle of Segregation.


1)1) All F1 plants had the normal phenotypeAll F1 plants had the normal phenotype

2)2) In both the first cross and reciprocal cross,In both the first cross and reciprocal cross, - Mutant phenotype not apparent in F1’s- Mutant phenotype not apparent in F1’s

- Mutant phenotype did reappear in F2’s- Mutant phenotype did reappear in F2’s - About ¼ of F2 plants had mutant- About ¼ of F2 plants had mutant

phenotype of dwarf or disease lesion.phenotype of dwarf or disease lesion.

Normal Mutant Ratio

F1 Plants 11 0 1:0

Normal Mutant Ratio

F2 Plants 99 33 3:1


3) Two types of plants had3) Two types of plants had the normal phenotypethe normal phenotype in the F2. About 1/3 ofin the F2. About 1/3 of the F2 normals werethe F2 normals were trubreeding while 2/3 trubreeding while 2/3

had mixed progeny had mixed progeny rows.rows.

4) Mutant F2 plants were4) Mutant F2 plants were truebreeding and all oftruebreeding and all of their F3 progeny weretheir F3 progeny were mutants.mutants.

F3 rows = 1:2:1F3 rows = 1:2:1F2F2


1)1) The variation in the dwarf and lesion traits was controlledThe variation in the dwarf and lesion traits was controlled by genes. Genes store the information that controls theby genes. Genes store the information that controls the expression of traits. Alternative versions of genes calledexpression of traits. Alternative versions of genes called alleles allow for the expression of different traits.alleles allow for the expression of different traits.

2)2) Genes are found in pairs in somatic cells that make upGenes are found in pairs in somatic cells that make up the plant.the plant.

3)3) Paired genes separate during gamete formation and onePaired genes separate during gamete formation and one gene from each pair goes into a gamete.gene from each pair goes into a gamete.

4)4) Gametes fuse at random during sexual reproductionGametes fuse at random during sexual reproduction producing the next generation seed.producing the next generation seed.

Documents

Experiment Summary Statements 1) The mutagen applied to the truebreeding seed induced phenotype variations in the soybeans. 2)The mutagen induced mutations