chapter 9

Chapter 9

Who’s the Who’s the Father of Modern Genetics??• 1843:

– Austrian monastery• Job =

– gardening

• 1851: – University of Vienna– Studied math and

science• Statistics!!!

Gregor Mendel!Gregor Mendel!

What did Mendel Experiment with?What did Mendel Experiment with?

• What plant?

• What about these plants?– Characteristics- heritable feature– Traits- genetically determined variant of a

characteristic

Characteristics and TraitsCharacteristics and Traits

Mendel’s ObservationsMendel’s Observations• Seeds from purple flowers produce...• Seeds from white flowers produce...• Seeds from tall plants...• Seeds from short pants...• This always true?

3 Steps of Mendel’s Experiments3 Steps of Mendel’s Experiments

1.1.

P: P:

Self PollinationSelf Pollination

2.2.

F1:F1:

Cross Cross Pollination Pollination

3.3.

F2: F2: Ratio of offspring:Ratio of offspring:

P generationP generation

FF1 1 Generation Generation

FF2 2 Generation Generation

Statistics 3 of 4 are purple Statistics 3 of 4 are purple

Cross-pollinationCross-pollination

Self-pollinationSelf-pollination

Mendel’s Experiments Mendel’s Experiments Continue...Continue...

• 100s of times100s of times• Lots of other traitsLots of other traits• All the same results!!All the same results!!• 3:1 phenotypic ratio3:1 phenotypic ratio

Mendel’s ConclusionsMendel’s Conclusions• What did he conclude?

– Something in the plant was a controlling factorSomething in the plant was a controlling factor

• What Did Mendel Hypothesize About Passing Traits?– Each trait independently controlledEach trait independently controlled

Review of His ResultsReview of His Results

RecessiveRecessive vs. vs. DominantDominant• ““Masked” when Masked” when

dominant presentdominant present AA, AaAA, Aa

• Expressed if no Expressed if no dominant presentdominant present aaaa

• Expressed if present Expressed if present at allat all

AA, AaAA, Aa

What are YOU?What are YOU?Class Ratios:

Conclusions: LAWSConclusions: LAWS• Law of segregation

– Pair of factors are separated during production of gametes.

• Why/How?– Online Animation!

http://my.hrw.com/sh2/sh07_10/student/flash/visual_concepts/60151.htm

Conclusions: LAWSConclusions: LAWS• Crossed plants w/2 different

characteristics (flower color, seed color)– Offspring showed traits from dominant

factors of each

• Law of Independent assortment– characteristics are inherited independent

of each other– Another Great Animation!


Pp

Yy

PY

Py

pY

pyPurple flower

Yellow seedPurple flowerGreen seed

White flowerYellow seed

White flowerGreen seed

Pair Share!

• 1st person: explain the Law of Segregation

• 2nd person: explain the Law of Independent Assortment

9.2 Part A

GENETIC CROSSES

Support for Mendel’s Conclusions Support for Mendel’s Conclusions

Molecular GeneticsMolecular GeneticsStudy of structure and function of genes Study of structure and function of genes

and chromosomesand chromosomes““Factors” are now called Factors” are now called ALLELESALLELES!!

Gene vs. AlleleGene vs. AllelePiece of DNATranscribed

proteinsSeveral on each

chromosome

Variants of genes Represented by letters

Symbols: Dom (capital)/Rec (small)

Flower color: P and pDom means...

Rec means...

Genome?

GENOTYPE AND GENOTYPE AND PHENOTYPE?PHENOTYPE?Genotype? Ex:

Phenotype? Ex:

Allele P p

P PP Pp

p Pp pp

Purple Purple WhiteWhite

Can different genotypes show the same phenotype?

Genotype Phenotype Genetic makeup of an organism

Visible appearance

Alleles inherited from parents

Environment may have an effect on phenotype

Homozygous and Homozygous and HeterozygousHeterozygous

Refer to genotypic or phenotypic?

Homozygous Both alleles are SAME AA or aa

Heterozygous Alleles are DIFFERENT Aa

What’s PROBABILITY?What’s PROBABILITY? Likelihood of something happening Percent, decimal or fraction

Probability =

# of times could happen

# of times expected

PROBABILITY PRACTICEPROBABILITY PRACTICE1000 plants

700 terminal flowers300 axial flowers

What is the probability that the next plant will have terminal flowers?

Axial? =

What’s a MONOHYBRID CROSS? Only one characteristic is tracked Produces a mono-hybrid

AA x aa Aa

What’s a Punnett Square? Diagram used to predict probabilities of

inherited traits in offspring

Allele A a

A

a

eggs

sper

m

6 types of monohybrid crosses:

Homozygous x Homozygous

Homozygous x Heterozygous

Heterozygous x Heterozygous

Testcross

Incomplete Dominance

Codominance

Allele

Homozygous dom x Hom rec

Homozygous Dom x Homozygous Rec

What genotypes?

Probability of Purple Flowers?

Probability of Heterozygous?

Remember Mendel’s Experiment?

Heterozygous x HeterozygousAllele

Heterozygous x Heterozygous Black coated bunnies (brown is

recessive) What genotypes?

Probability for Black?

Homozygous?

Heterozygous?

Homozygous Dominant x Heterozygous

Allele

Hom. Dom. x Heterozygous

Black guinea pigs (dom), brown (rec)

What genotypes?

Probability for Black?

Homozygous?

Heterozygous?

Testcross: animation What genotype do you test it with? Hom recessive x Unknown genotype

You are Given a Black Guinea pig. How do you determine the Genotype?

If you end up with three black guinea pigs and one brown what was the genotype of the unknown guinea pig?

Allele

REVIEWREVIEW

Homozygous?Homozygous? Heterozygous?Heterozygous? Genotype?Genotype? Phenotype?Phenotype? Testcross?Testcross? Dominant?Dominant? Recessive?Recessive?

Practice w/monohybrid punnett squaresPractice w/monohybrid punnett squares Square activitySquare activity

OPENER, Wed. 12/2OPENER, Wed. 12/2You’re TURNING THIS IN, in 7 minutes!!Use “D” and “d” for the alleles, make a punnett square for each:

D = Dodo Head d = Wiz Kid1. Purebred Dodo Head x Wiz kid2. Heterozygous x Wiz kid3. Hybrid Dodo Head x Homozygous Dodo Head Then, for each scenario, find the probability of:

a. Dodo Heads?b. Wiz Kids?c. Purebred Dodo Headsd. Heterozygous offspring

OPENER, Wed. 12/2OPENER, Wed. 12/2 You’re TURNING THIS IN, in 7 minutes!! Use “D” and “d” for the alleles, make a

punnett square for each:D = Dodo Head d = Wiz Kid

1. Purebred Dodo Head x Wiz kid

2. Heterozygous x Wiz kid

3. Hybrid Dodo Head x Homozygous Dodo Head

Then, for each scenario, find the probability of:

a. Dodo Heads?

b. Wiz Kids?

c. Purebred Dodo Heads

d. Heterozygous offspring

Monohybrid Cross LabMonohybrid Cross Lab

Alleles, gametes, genotypes, phenotypes, Alleles, gametes, genotypes, phenotypes, Punnett Squares, & probabilitiesPunnett Squares, & probabilities

Write your Write your BAG #sBAG #s on your data sheet! on your data sheet!

COUNT all of your pieces before you beginCOUNT all of your pieces before you begin

You’re drawing from the bags FORTY times You’re drawing from the bags FORTY times today...get going! Follow the directions today...get going! Follow the directions CAREFULLYCAREFULLY!!

We’ll finish up after the lab with more We’ll finish up after the lab with more examples.examples.

Group #

(Bag #)# BB # Bb # bb

1

2

3

4

5

6

7

8

9

10

11

12

HomeworkHomework::Earth Force Assignment

Family History—Health Surveys

And...book:

9.2 B MORE Genetic Crosses

Some Weirdo Stuff!Incomplete dominance

CodominanceMultiple allelesPolygenic traits

Inheritance Patterns:

Yesterday: Complete Dominance

One allele completely masks the other Homozygous Dominant & Heterozygous are

indistinguishable

Incomplete Dominance Phenotype of heterozygote is in between

dominant and recessive

Incomplete Dominance Example

Red Flowering four o’ clocks or snapdragons

Reds self pollinate and produce only reds Whites = whites

Cross pollination?

PINK!!!PINK!!!Genotypes:Genotypes:

Punnett square for two Pink flowers

How many Reds? Pinks? Whites?

What is the phenotypic ratio for red:pink:white

Genotypic ratio?

Codominance Both alleles expressed in heterozygotes

Alleles are not “dominant & recessive” Do not blend either

What does the heterozygous phenotype look like?

Example: AB Blood type

Blood TypesMultiple Alleles:

A, B, i (O)Genotypes:

Phenotypes:

Codominance:A & BNeither is dominant or recessive!!!Show both traits A and B

If Mom is type AB and Dad is type O, what are the probabilities of the offspring?

Universal Recipient

Universal Donor

Polygenic TraitsPoly =

Genic =

Ex:

DIHYBRID CROSSES..Say What?

Two characteristics are tracked

Produces a DIHYBRID!

Let’s see....

DIHYBRID Example!

Homozygous Dominant x homozygous recessive

Round, Yellow seeds x wrinkled, green seeds

Round/wrinkled : R, rYellow/green: Y, y

RRYY x rryy

Genotypic ratio?

Phenotypic ratio?

What What goes goes here?here?

Heterozygous x Heterozygous Phenotypes?

Genotypes? RrYy x RrYy

Phenotypes & ratio?

Genotypes & ratio?

Dihybrid Dihybrid ActivityActivity TWO sets of bags! READ CAREFULLY! DON’T mix up the bags, double check

your # in each at start and at end!

QUESTIONS on ½ sheet DUE QUESTIONS on ½ sheet DUE WEDNESDAY—EACH PERSON DOES WEDNESDAY—EACH PERSON DOES INDIVIDUALLY!INDIVIDUALLY!

Opener, Mon. Opener, Mon. 12/112/1

I’M ALSO COLLECTING YOUR EARTH FORCE ASSIGNMENT & YOUR FAMILY HEALTH SURVEYS TODAY!

TURN THIS IN: Make a Punnett square for the following

parent genotypes: SsYy x SsYy What are the genotypic ratios? Phenotypic Ratios?

SsYy x SsYySsYy x SsYyGenotypic ratios?Genotypic ratios?Phenotypic Ratios?Phenotypic Ratios?

LabLab Finish your questions at home if you are Finish your questions at home if you are

not finished!not finished!

When you finish, we’ll share data so you When you finish, we’ll share data so you can answer the questions.can answer the questions.

chapter 9

Documents

purple flowers

dominant present aaexpressed

characteristic characteristics

purple crosspollinationself

monohybridaa x aa aawhats

dominant factors of

tall plants

white flowers