Independent Assortment

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Independent Assortment Non-Mendelian Genetics

• EQ What are the other outcomes of a cross?

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Learning Goal - Genetics

• 4 I can predict the offspring of different
  crosses of parents and explain how the traits
  were inherited. I can apply monohybrid crosses to
  a dihybrid cross (Ex RRYY x rryy)
• 3 I can usually find the probability of the
  offspring and I understand meiosis
• 2 I can do basic Punnett squares but still need
  help setting it up
• 1 I need to review genetics

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I. Mendelian Genetics A. Dominant Recessive
Review

• One allele is DOMINANT over the other (because
  the dominant allele can mask the recessive
  allele)

genotype PP
genotype pp
genotype Pp
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Review Problem A. Dominant Recessive

• In pea plants, purple flowers (P) are dominant
  over white flowers (p). Show the cross between
  two heterozygous plants.

P p
GENOTYPES

- PP (25) Pp (50) pp (25) - ratio 121
P p

PHENOTYPES
- purple (75) white (25) - ratio 31
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B. Two Cross/Dihybrid Cross

• Mendel wondered if one allele for one gene would
  influence another allele for a separate gene
• RRYY x rryy
• (R) is round, (r) is wrinkled
• (Y) is yellow, (y) is green
• He found the two factor/dihybrid cross

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Example 1 F1 RRYY x rryy




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Example 2 F2 RrYy x RrYy




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9331
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What did Mendel find?

• In a two factor cross, the alleles would separate
  independently (not linked).
• Ratio for the F2 generation was 9331

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Review Dihybrid Crosses

• Tall TT
• Tall Tt
• Short tt
• Red RR
• Red Rr
• Yellow rr

• Cross two heterozygous plants for both traits.

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TtRr X TtRr




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TtRr X TtRr

• TR Tr tR tr
• TR TTRR TTRr TtRR TtRr
• Tr TTRr TTrr TtRr Ttrr
• tR TtRR TtRr ttRR ttRr
• tr TtRr Ttrr ttRr ttrr

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TtRr X TtRr




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NNDD x NnDd




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II. Non-Mendelian Genetics

• Incomplete Dominance
• Codominance
• Multiple Alleles
• Polygenic Traits
• Sex-Linked Traits

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A. Incomplete Dominance

• a third (new) phenotype appears in the
  heterozygous condition as a BLEND of the
  dominant and recessivephenotypes.
• Ex - Dominant Red (R) Recessive White (r)
  Hybrid Pink (Rr)

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Example 3 Incomplete Dominance

• Show the cross between a red and a white flower.

GENOTYPES

- RR (0) Rr (100) rr (0) - ratio 40

PHENOTYPES

• pink (100) white (0) red (0)

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Example 4 Incomplete Dominance

• Show the cross between a pink and a white flower.

GENOTYPES

- RR (0) Rr (50) rr (50) - ratio 11

PHENOTYPES
- pink (50) white (50) - ratio 11
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B. Codominance

• in the heterozygous condition, both alleles are
  expressed equally with NO blending! Represented
  by using two DIFFERENT capital letters.
• Example
• Dominant Black (B) Dominant White (W)
• Speckled Black and White Phenotype (BW)

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Codominance Example Speckled Chickens

• BB black feathers
• WW white feathers
• BW black white speckled feathers
• Notice
• NO GRAY!
• NO BLEND!
• Each feather is
• either black or white

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Codominance Example 5 Rhodedendron

• R allele for red flowers
• W allele for white flowers
• Cross a homozygous red flower with a homozygous
  white flower.

• Note that its not blended or light pink

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Codominance ExampleRoan cattle

• cattle can be red (RR all red hairs)
  white (WW all white hairs) roan (RW
  red and white hairs together)

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Codominance Example 6Appaloosa horses

• Gray horses (GG) are codominant to white horses
  (WW). The heterozygous horse (GW) is an
  Appaloosa (a white horse with gray spots).
• Cross a white horse with an appaloosa horse.

W W
G W
GW
GW

WW
WW
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Codominance Example 7

• Sickle Cell Anemia blood disorder commonly
  found in Africans (1 in 500)

sick
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Example 7 Sickle Cell Codominance

• Show the cross between an individual with
  sickle-cell anemia and another who is a carrier
  but not sick.

N S
GENOTYPES
- NS (50) SS (50) - ratio 11
S S
PHENOTYPES
- carrier (50) sick (50) - ratio 11
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C. Multiple Alleles

• there are more than two alleles for a gene.
• Ex blood type consists of two dominant and one
  recessive allele options.
• Allele A B are
• dominant over
• Allele O (i)

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Multiple AllelesBlood Types (A, B, AB, O)

• Rules for Blood Types
• A and B are co-dominant (Both show)
• AA or IAIA type A
• BB or IBIB type B
• AB or IAIB type AB
• A and B are dominant over O (Regular dom/rec)
• AO or IAi type A
• BO or IBi type B
• OO or ii type O

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Multiple AllelesBlood Types (A, B, AB, O)
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Phenotype Possible Genotype(s) Allele (antigen) on RBC surface Can Donate Blood To Can Receive Blood From
A IAi IAIA A A, AB A, O
B IBi IBIB B B, AB B, O
AB IAIB AB AB A, B, AB, O
O ii O A, B, AB, O O
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Example 8 Multiple Alleles

• Show the cross between a mother who has type O
  blood and a father who has type AB blood.

GENOTYPES
i i
- Ai (50) Bi (50) - ratio 11
A B
PHENOTYPES
- type A (50) type B (50) - ratio 11
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Example 9 Multiple Alleles

• Show the cross between a mother who is
  heterozygous for type B blood and a father who is
  heterozygous for type A blood.

GENOTYPES
A i

• AB (25) Bi (25)
• Ai (25) ii (25)
• - ratio 1111

B i
PHENOTYPES

• type AB (25) type B (25)
• type A (25) type O (25)
• - ratio 1111

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Multiple AllelesLab Mouse Fur Colors

• Fur colors (determined by 4 alleles) black
  agouti yellow
  (white)

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Multiple AllelesRabbit Fur Colors

• Fur colors (determined by 4 alleles) full,
  chinchilla, himalayan, albino

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D. Polygenic Traits

• traits produced by multiple genes
• example skin color, tallness, eye color

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E. Sex-Linked Traits

• Gene is attached to the X chromosome only, not
  found on the Y chromosome at all.
• (women have XX, men have XY chromosomes). These
  disorders are more common in boys.
• Examples
• red-green colorblindness
• Hemophilia
• baldness

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Sex-Linked Traits

• in males, there is no second X chromosome to
  mask a recessive gene. If they get an X with
  the disorder, they have it. Girls must inherit
  defective Xs from both parents.

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Sex-Linked Traits

• A 29, B 45, C --, D 26
• ? Normal vision
• A 70, B --, C 5, D --
• ? Red-green color blind
• A 70, B --, C 5, D 6
• ? Red color blind
• A 70, B --, C 5, D 2
• ? Green color blind

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Chromosomal Disorders

• When too many/few chromosomes produced from
  meiosis

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Trisomy 21 Down Syndrome
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Other Chromosomal Abnormalities

• http//learn.genetics.utah.edu/content/disorders/c
  hromosomal/