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

And can you answer this? And can you answer this? Which of the following pairs of crosses results in the same phenotypic ratios? A)Aa x Aa and AA x aa B)AA x aa and AA x Aa C)AA x Aa and Aa x aa D)None of the above

EVIDENCE FROM GENETICS EVIDENCE FROM GENETICS  Deduction: If the hypothesis of evolution is correct, then we should see evidence of this in genetics  Background: Gregor Mendel ( Experiments with the garden pea. His paper in 1866 established the field of genetics.

MENDEL’S GARDEN MENDEL’S GARDEN

Mendel at work Mendel at work

Mendel’s Traits

Monohybrid Crosses (=Breeding experiments involving one trait) Monohybrid Crosses (=Breeding experiments involving one trait)  Pea plants  P Tall x Tall Short x Short  F 1 All Tall All Short

Monohybrid Crosses (=Breeding experiments involving one trait) Monohybrid Crosses (=Breeding experiments involving one trait)  Pea plants  P Tall x Tall Short x Short  F 1 All Tall All Short  F 2 All Tall The tall trait is dominant

Monohybrid Crosses (=Breeding experiments involving one trait) Monohybrid Crosses (=Breeding experiments involving one trait)  Pea plants  P Tall x Tall Short x Short  F 1 All Tall All Short  F 2 F 2 x F 2 All Tall

Monohybrid Crosses (=Breeding experiments involving one trait) Monohybrid Crosses (=Breeding experiments involving one trait)  Pea plants  P Tall x Tall Short x Short  F 1 All Tall All Short  F 2 F 2 x F 2  F 3 75% Tall, 25% Short All Tall

MENDEL’S TRAITS  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  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 analyzes the data Traits passed in the gametes Pollen (sperm) & eggs Note: ¾ Tall= TT, Tt, tT ¼ Short= 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 2 particles (factors) determine a trait

Using a Punnett Square T t T t T TT Tt T TT Tt t Tt tt t Tt tt Alleles= Alternative forms of the same gene (T or t) Suppose Tt X Tt

Using a Punnett Square Eggs Eggs T t T t T TT Tt T TT TtPollen t Tt tt t Tt tt Tall Short

Using a Punnett Square T t T t T TT Tt T TT Tt t Tt tt t Tt tt Homozygous condition= both alleles are alike (TT or tt)

Using a Punnett Square T t T t T TT Tt T TT Tt t Tt tt t Tt tt Heterozygous condition= both alleles are different (Tt)

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? A)Both parents had blue eyes. B)One parent had blue & the other was homozygous dominant C)Both parents had brown eyes. D)One parent had blue & the other was heterozygous E)Both parents were heterozygous.

Dihybrid Crosses (=Breeding experiments involving two traits) Round (R) or Wrinkled (r) seeds Round (R) or Wrinkled (r) seeds Yellow (Y) or Green (y) seeds Yellow (Y) or Green (y) seeds P RRYY x rryy F 1 RrYy Genotype Round Yellow Phenotype Round Yellow Phenotype

Dihybrid Cross RrYy x RrYy Dihybrid Cross RrYy x RrYy

Clicker Question What belongs in the red square? Clicker Question What belongs in the red square?  A) RRYY  B) RrYY  C rrYy  D) rrYY  E) rryy

Dihybrid Cross RrYy x RrYy Dihybrid Cross RrYy x RrYy

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 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 RrYy Dihybrid Cross RrYy x RrYy 9: 3: 3: 1 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 BUT

What if RY are linked together & ry are linked together ? Non Independent Assortment

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

And can you answer this? And can you answer this? Which of the following pairs of crosses results in the same phenotypic ratios? A)Aa x Aa and AA x aa B)AA x aa and AA x Aa C)AA x Aa and Aa x aa D)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? A)0% B)25% C)50% D)75% E)100%