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EVIDENCE FROM GENETICS. Can you answer this?. Which represents a monohybrid cross between a homozygous recessive and a heterozygote? A) Tt x Tt B) ttmm x TtMm C) tt x Tt D) ttmm x TTMM. Can you answer this?. In rats, black fur is dominant over white.

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Evidence from genetics
EVIDENCE FROM GENETICS


Can you answer this
Can you answer this?

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

A) Tt x Tt

B) ttmm x TtMm

C) tt x Tt

D) ttmm x TTMM


Can you answer this1
Can you answer this?

In rats, black fur is dominant over white.

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

  • 0%

  • 25%

  • 50%

  • 75%


And can you answer this
And can you answer this?

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

  • Aa x Aa and AA x aa

  • AA x aa and AA x Aa

  • AA x Aa and Aa x aa

  • None of the above


Evidence from genetics1
EVIDENCE FROM GENETICS

  • Deduction: If the hypothesis of evolution is correct, then we should see evidence of this in genetics

  • Background:

    Gregor Mendel (1822-1884

    Experiments with the garden pea.

    His paper in 1866 established the field of genetics.






Monohybrid crosses breeding experiments involving one trait
Monohybrid Crosses(=Breeding experiments involving one trait)

  • Pea plants

  • P Tall x Tall Short x Short

  • F1 All Tall All Short


Monohybrid crosses breeding experiments involving one trait1
Monohybrid Crosses(=Breeding experiments involving one trait)

  • Pea plants

  • P Tall x Tall Short x Short

  • F1 All Tall All Short

  • F2 All Tall

The tall trait is dominant


Monohybrid crosses breeding experiments involving one trait2
Monohybrid Crosses(=Breeding experiments involving one trait)

  • Pea plants

  • P Tall x Tall Short x Short

  • F1 All Tall All Short

  • F2 F2 x F2

All Tall


Monohybrid crosses breeding experiments involving one trait3
Monohybrid Crosses(=Breeding experiments involving one trait)

  • Pea plants

  • P Tall x Tall Short x Short

  • F1 All Tall All Short

  • F2 F2 x F2

  • F3 75% Tall, 25% Short

All Tall

3:1 Ratio


Mendel s traits1

5474/1850= 2.96

6022/2001= 3.01

882/299= 2.95

428/152= 2.82

705/224= 3.15

651/207= 3.14

787/277= 2.84

MENDEL’S TRAITS


Mendel s traits2

5474/1850= 2.96

6022/2001= 3.01

882/299= 2.95

428/152= 2.82

705/224= 3.15

651/207= 3.14

787/277= 2.84

MENDEL’S TRAITS

3:1

Ratio


Mendel analyzes the data
Mendel analyzes the data

Traits passed in the gametes

Pollen (sperm) & eggs

Note: ¾ Tall= TT, Tt, tT

¼ Short= tt

3:1 Phenotypic Ratio


Terms and principles
Terms and Principles

  • Dominant (e.g. Tall)

  • Recessive (e.g. Short)

  • Phenotype (visible characteristics)

  • Genotype (genetic characteristics)

  • Particulate theory of inheritance=

    2 particles (factors) determine a trait

Blending hypothesis is wrong!


Using a punnett square
Using a Punnett Square

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

T t

T TT Tt

t Tt tt

Suppose Tt X Tt


Using a punnett square1
Using a Punnett Square

Note: 3:1 ratio

Eggs

T t

T TT Tt

Pollen

t Tt tt

Tall

Tall

Short

Tall


Using a punnett square2
Using a Punnett Square

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

T t

T TT Tt

t Tt tt


Using a punnett square3
Using a Punnett Square

Heterozygous condition= both alleles are different (Tt)

T t

T TT Tt

t Tt tt


Clicker question
Clicker Question

  • Blue eyes (b) are recessive to brown (B).Suppose 2 parents had 11 children: 6 with blue and 5 with brown. Which of these statements is most likely to be right?

  • Both parents had blue eyes.

  • One parent had blue & the other was homozygous dominant

  • Both parents had brown eyes.

  • One parent had blue & the other was heterozygous

  • Both parents were heterozygous.


Dihybrid crosses breeding experiments involving two traits
Dihybrid Crosses(=Breeding experiments involving two traits)

Round (R) or Wrinkled (r) seeds

Yellow (Y) or Green (y) seeds

P RRYY x rryy

F1 RrYy Genotype

Round Yellow Phenotype


Dihybrid cross rryy x rryy
Dihybrid Cross RrYy x RrYy

Set up a Punnet Square


Dihybrid cross rryy x rryy1
Dihybrid Cross RrYy x RrYy


Dihybrid cross rryy x rryy2
Dihybrid Cross RrYy x RrYy

Fill in this line first


Dihybrid cross rryy x rryy3
Dihybrid CrossRrYy x RrYy

Now fill in the rest


Clicker question what belongs in the red square
Clicker QuestionWhat belongs in the red square?

  • A) RRYY

  • B) RrYY

  • C rrYy

  • D) rrYY

  • E) rryy


Dihybrid cross rryy x rryy4
Dihybrid CrossRrYy x RrYy


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

  • A) All 16

  • B) 9 out of 16

  • C) 50%

  • D) 3 0ut of 16

  • E) 1 out of 16


Clicker question how many wrinkled green seeds will there be out of 16 possibilities1
Clicker Question:How many wrinkled green seeds will there be out of 16 possibilities?

  • A) All 16

  • B) 9 out of 16

  • C) 50%

  • D) 3 0ut of 16

  • E) 1 out of 16


Dihybrid cross rryy x rryy5
Dihybrid CrossRrYy x RrYy

9: 3: 3: 1

Round Round Wrinkled Wrinkled

Yellow Green Yellow Green


Principle of independent assortment
Principle of Independent Assortment

= Factors (genes) sort independently of one another.

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

BUT


What if ry are linked together ry are linked together
What ifRY are linked together & ry are linked together ?

Non Independent Assortment


Can you answer this2
Can you answer this?

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

A) Tt x Tt

B) ttmm x TtMm

C) tt x Tt

D) ttmm x TTMM


Can you answer this3
Can you answer this?

In rats, black fur is dominant over white.

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

  • 0%

  • 25%

  • 50%

  • 75%


And can you answer this1
And can you answer this?

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

  • Aa x Aa and AA x aa

  • AA x aa and AA x Aa

  • AA x Aa and Aa x aa

  • None of the above


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

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

  • 0%

  • 25%

  • 50%

  • 75%

  • 100%

B

E

D

A

C


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