EVIDENCE FROM GENETICS

EVIDENCE FROMEVIDENCE FROM GENETICS GENETICS

Can you answer this?Can you answer this?

Which represents a monohybrid cross Which represents a monohybrid cross between a homozygous recessive and a between a homozygous recessive and a heterozygote?heterozygote?

A) Tt x TtA) Tt x Tt B) ttmm x TtMmB) ttmm x TtMm C) tt x TtC) tt x Tt D) ttmm x TTMMD) ttmm x TTMM

Can you answer this? Can you answer this?

In rats, black fur is dominant over white.In rats, black fur is dominant over white.If a white rat is crossed with a If a white rat is crossed with a

heterozygous black rat, what is the heterozygous black rat, what is the likely % of the offspring that will be likely % of the offspring that will be white? white?

A)A) 0%0%B)B) 25%25%C)C) 50%50%D)D) 75%75%

And can you answer And can you answer this?this?

Which of the following pairs Which of the following pairs of crosses results in of crosses results in the same phenotypic the same phenotypic ratios?ratios?

A)A) Aa x Aa and AA x aaAa x Aa and AA x aa

B)B) AA x aa and AA x AaAA x aa and AA x Aa

C)C) AA x Aa and Aa x aaAA x Aa and Aa x aa

D)D) None of the aboveNone of the above

EVIDENCE FROMEVIDENCE FROM GENETICS GENETICS

Deduction: Deduction: IfIf the hypothesis of the hypothesis of evolution is correct, evolution is correct, thenthen we should we should see evidence of this in geneticssee evidence of this in genetics

Background:Background:Gregor Mendel (1822-1884Gregor Mendel (1822-1884Experiments with the garden pea.Experiments with the garden pea.His paper in 1866 established the His paper in 1866 established the

field of genetics.field of genetics.

MENDEL’S GARDENMENDEL’S GARDEN

Mendel at workMendel at work

Mendel’s TraitsMendel’s Traits

Monohybrid CrossesMonohybrid Crosses (=Breeding experiments involving one trait)(=Breeding experiments involving one trait)

Pea plantsPea plants P Tall x Tall Short x ShortP Tall x Tall Short x Short

FF1 1 All Tall All ShortAll Tall All Short




FF2 2 All TallAll Tall

The tall trait is dominant




FF22 FF22 x x FF22

All Tall




FF22 FF22 x x FF22

FF3 3 75% Tall, 25% Short75% Tall, 25% Short

All Tall

MENDEL’S TRAITS MENDEL’S TRAITS 5474/1850=5474/1850= 2.962.96 6022/2001=6022/2001= 3.013.01 882/299=882/299= 2.952.95 428/152=428/152= 2.822.82

705/224=705/224= 3.153.15

651/207=651/207= 3.143.14

787/277=787/277= 2.842.84

Mendel analyzes the dataMendel analyzes the data

Traits passed in the gametesTraits passed in the gametesPollen (sperm) & eggsPollen (sperm) & eggs

Note: ¾ Tall= TT, Tt, tTNote: ¾ Tall= TT, Tt, tT ¼ Short= tt¼ Short= tt

3:1 Phenotypic Ratio3:1 Phenotypic Ratio

Terms and PrinciplesTerms and Principles Dominant (e.g. Tall)Dominant (e.g. Tall) Recessive (e.g. Short)Recessive (e.g. Short)

Phenotype (visible characteristics)Phenotype (visible characteristics) Genotype (genetic characteristics)Genotype (genetic characteristics) Particulate theory of inheritanceParticulate theory of inheritance= =

2 particles (factors) determine a trait2 particles (factors) determine a trait

Using a Punnett SquareUsing a Punnett Square

T tT t

T TT TtT TT Tt

t Tt ttt Tt tt

Alleles= Alternative forms of the same gene (T or t)

Suppose Tt X Tt


Eggs Eggs

T tT t

T TT TtT TT Tt

Pollen Pollen

t Tt ttt Tt tt

Tall Tall

Tall

Short


T tT t

T T TTTT Tt Tt

t Tt t Tt tttt

Homozygous condition= both alleles are alike (TT or tt)


T tT t

T TT T TT TtTt

t t Tt Tt tt tt

Heterozygous condition= both alleles are different (Tt)

Clicker QuestionClicker Question Blue eyes (b) are recessive to brown (B).Blue eyes (b) are recessive to brown (B).

Suppose 2 parents had 11 children: 6 with blue Suppose 2 parents had 11 children: 6 with blue and 5 with brown. Which of these statements is and 5 with brown. Which of these statements is most likely to be right?most likely to be right?

A)A) Both parents had blue eyes.Both parents had blue eyes.

B)B) One parent had blue & the other was homozygous One parent had blue & the other was homozygous dominantdominant

C)C) Both parents had brown eyes.Both parents had brown eyes.

D)D) One parent had blue & the other was heterozygousOne parent had blue & the other was heterozygous

E)E) Both parents were heterozygous.Both parents were heterozygous.

Dihybrid CrossesDihybrid Crosses(=Breeding experiments involving two traits)(=Breeding experiments involving two traits)

Round (R) or Wrinkled (r) seedsRound (R) or Wrinkled (r) seeds

Yellow (Y) or Green (y) seedsYellow (Y) or Green (y) seeds

P RRYY x rryyP RRYY x rryy

FF1 1 RrYy Genotype RrYy Genotype

Round Yellow PhenotypeRound Yellow Phenotype

Dihybrid Cross Dihybrid Cross RrYy x RrYyRrYy x RrYy

Dihybrid CrossDihybrid Cross RrYy x RrYyRrYy x RrYy

Clicker QuestionClicker QuestionWhat belongs in the red square?What belongs in the red square?

A)A) RRYY RRYY B)B) RrYY RrYY C rrYyC rrYy D) rrYYD) rrYY E) rryyE) rryy

Clicker Question:Clicker Question:How many wrinkled green seeds will there How many wrinkled green seeds will there be out of 16 possibilities?be out of 16 possibilities?

A) All 16A) All 16 B) 9 out of 16B) 9 out of 16 C) 50%C) 50% D) 3 0ut of 16D) 3 0ut of 16 E) 1 out of 16E) 1 out of 16


9: 3: 3: 19: 3: 3: 1

Round Round Wrinkled WrinkledRound Round Wrinkled Wrinkled

Yellow Green Yellow GreenYellow Green Yellow Green

Principle of Principle of Independent Assortment Independent Assortment

= Factors (genes) sort independently of = Factors (genes) sort independently of one another.one another.

i.e. all possible combinations of Y and y i.e. all possible combinations of Y and y and R and r occurand R and r occur

BUTBUT

What ifWhat ifRY are linked together &RY are linked together &

ry are linked together ?ry are linked together ?

Non Independent Assortment

Can you answer this?Can you answer this?

Which represents a monohybrid cross Which represents a monohybrid cross between a homozygous recessive and a between a homozygous recessive and a heterozygote?heterozygote?

A) Tt x TtA) Tt x Tt B) ttmm x TtMmB) ttmm x TtMm C) tt x TtC) tt x Tt D) ttmm x TTMMD) ttmm x TTMM

Can you answer this? Can you answer this?

In rats, black fur is dominant over white.In rats, black fur is dominant over white.If a white rat is crossed with a If a white rat is crossed with a

heterozygous black rat, what is the heterozygous black rat, what is the likely % of the offspring that will be likely % of the offspring that will be white? white?

A)A) 0%0%B)B) 25%25%C)C) 50%50%D)D) 75%75%

And can you answer And can you answer this?this?

Which of the following pairs Which of the following pairs of crosses results in of crosses results in the same phenotypic the same phenotypic ratios?ratios?

A)A) Aa x Aa and AA x aaAa x Aa and AA x aa

B)B) AA x aa and AA x AaAA x aa and AA x Aa

C)C) AA x Aa and Aa x aaAA x Aa and Aa x aa

D)D) None of the aboveNone of the above

According to J.K. Rowling wizards & witches can According to J.K. Rowling wizards & witches can be born from pure bloods or muggles. Suppose be born from pure bloods or muggles. Suppose the wizard/witch trait is recessive (m)the wizard/witch trait is recessive (m)and the muggle trait is dominant (M)and the muggle trait is dominant (M)

Hermione is a witch born Hermione is a witch born of muggle parents. If her of muggle parents. If her parents had another child parents had another child what are the chances that what are the chances that that one also would be a that one also would be a wizard or witch?wizard or witch?

A)A) 0%0%

B)B) 25%25%

C)C) 50%50%

D)D) 75%75%

E)E) 100%100%

EVIDENCE FROM GENETICS

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