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Non-Mendelian Genetics. phenotype: purple. phenotype: white. phenotype: purple. Mendelian Genetics: 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. PP. Pp. Pp.

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mendelian genetics dominant recessive review

phenotype: purple

phenotype: white

phenotype: purple

Mendelian Genetics: 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

review problem dominant recessive

PP

Pp

Pp

pp

Review Problem: 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 1:2:1

P

p

PHENOTYPES:

- purple (75%) white (25%)

- ratio 3:1

non mendelian genetics1
Non-Mendelian Genetics
  • Incomplete Dominance
  • Codominance
  • Multiple Alleles
  • Polygenic Traits
  • Sex-Linked Traits
incomplete dominance

RR = red

rr = white

Rr = pink

Incomplete Dominance
  • a third (new) phenotype appears in the heterozygouscondition as a BLEND of the dominant and recessivephenotypes. Ex - Dominant Red (R) + Recessive White (r) = Hybrid Pink (Rr)
problem incomplete dominance

R r

r

r

Rr

Rr

rr

rr

Problem: Incomplete Dominance
  • Show the cross between a pink and a white flower.

GENOTYPES:

- RR (0%) Rr (50%) rr (50%)

- ratio 1:1

PHENOTYPES:

- pink (50%); white (50%)

- ratio 1:1

codominance

NS = some of each

SS = sickle cells

NN = normal cells

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)
  • Sickle Cell Anemia -

sick

codominance example speckled chickens
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

codominance example rhodedendron
Codominance Example: Rhodedendron
  • R = allele for red flowers
  • W = allele for white flowers
  • Cross a homozygous red flower with a homozygous white flower.
codominance example roan cattle
Codominance Example:Roan cattle
  • cattle can be red (RR – all red hairs) white (WW – all white hairs) roan (RW – red and white hairs together)
codominance example appaloosa horses
Codominance Example:Appaloosa 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

problem codominance

NS

SS

SS

NS

Problem: 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 1:1

S

S

PHENOTYPES:

- carrier (50%) sick (50%)

- ratio 1:1

multiple alleles
Multiple Alleles
  • there are more than twoalleles for a gene. Ex – blood type consists of two dominant and one recessive allele

options. Allele A

and B are

dominant over

Allele O (i)

multiple alleles lab mouse fur colors
Multiple Alleles:Lab Mouse Fur Colors
  • Fur colors (determined by 4 alleles): black agouti yellow
multiple alleles rabbit fur colors
Multiple Alleles:Rabbit Fur Colors
  • Fur colors (determined by 4 alleles): full, chinchilla, himalayan, albino
multiple alleles blood types a b ab o
Multiple Alleles:Blood 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

problem multiple alleles

Ai

Ai

Bi

Bi

Problem: 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 1:1

A

B

PHENOTYPES:

- type A (50%) type B (50%)

- ratio 1:1

problem multiple alleles1

Bi

AB

Ai

ii

Problem: 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 1:1:1:1

B

i

PHENOTYPES:

  • type AB (25%); type B (25%)
  • type A (25%); type O (25%)
  • - ratio 1:1:1:1
polygenic traits
Polygenic Traits
  • traits produced by multiple genes
  • example: skin color
sex linked traits
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
sex linked traits1
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 X’s from both parents.
sex linked traits2
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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