Codominance, Incomplete Dominance, Blood Types - Practice Worksheet - Free Printable

The image you uploaded contains a worksheet on codominance and incomplete dominance, two important concepts in genetics. Below, I will explain the key ideas and solve the problems step by step.

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1. Codominance: Blood Types

Codominance occurs when both alleles of a gene are expressed equally in the phenotype of heterozygotes. For blood types, the alleles involved are:
- A: Type A
- B: Type B
- O: Type O (recessive)

#### Key Rules for Blood Types:
1. AA or AO: Phenotype is Type A
2. BB or BO: Phenotype is Type B
3. AB: Phenotype is Type AB (both A and B antigens are present)
4. OO: Phenotype is Type O

#### Example Problems:
##### Problem 1: AA x BB
- Parents: AA (Type A) and BB (Type B)
- Possible Genotypes of Offspring: All offspring will be AB.
- Phenotype: Type AB (both A and B antigens are present).

##### Problem 2: AA x OO
- Parents: AA (Type A) and OO (Type O)
- Possible Genotypes of Offspring: All offspring will be AO.
- Phenotype: Type A (A allele is dominant over O).

##### Problem 3: AB x OO
- Parents: AB (Type AB) and OO (Type O)
- Possible Genotypes of Offspring: AO and BO.
- Phenotypes:
- AO → Type A
- BO → Type B

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2. Incomplete Dominance: Chicken Feathers

In incomplete dominance, neither allele is completely dominant over the other. Instead, the heterozygote expresses an intermediate phenotype. For chicken feathers:
- BB: Black feathers
- WW: White feathers
- BW: Gray feathers (intermediate between black and white)

#### Example Problems:
##### Problem 1: BW x WW
- Parents: BW (Gray) and WW (White)
- Possible Genotypes of Offspring: BW and WW.
- Phenotypes:
- BW → Gray
- WW → White

##### Problem 2: WW x WW
- Parents: WW (White) and WW (White)
- Possible Genotypes of Offspring: All WW.
- Phenotype: White

##### Problem 3: BB x BB
- Parents: BB (Black) and BB (Black)
- Possible Genotypes of Offspring: All BB.
- Phenotype: Black

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3. Incomplete Dominance: Cow Fur Color

For cow fur color:
- RR: Red fur
- RW: Roan fur (intermediate between red and white)
- WW: White fur

#### Example Problems:
##### Problem 1: RR x WW
- Parents: RR (Red) and WW (White)
- Possible Genotypes of Offspring: All RW.
- Phenotype: Roan

##### Problem 2: RW x RW
- Parents: RW (Roan) and RW (Roan)
- Possible Genotypes of Offspring: RR, RW, WW.
- Phenotypes:
- RR → Red
- RW → Roan
- WW → White

##### Problem 3: RW x RR
- Parents: RW (Roan) and RR (Red)
- Possible Genotypes of Offspring: RR and RW.
- Phenotypes:
- RR → Red
- RW → Roan

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Definitions

- Codominance: Both alleles are fully expressed in the phenotype of heterozygotes. Example: Blood types (AB).
- Incomplete Dominance: The heterozygote expresses an intermediate phenotype. Example: Chicken feathers (gray), cow fur (roan).

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Final Answers

1. Codominance: Blood Types
- AA x BB: All offspring are AB (Type AB).
- AA x OO: All offspring are AO (Type A).
- AB x OO: Offspring are AO (Type A) and BO (Type B).

2. Incomplete Dominance: Chicken Feathers
- BW x WW: Offspring are BW (Gray) and WW (White).
- WW x WW: All offspring are WW (White).
- BB x BB: All offspring are BB (Black).

3. Incomplete Dominance: Cow Fur Color
- RR x WW: All offspring are RW (Roan).
- RW x RW: Offspring are RR (Red), RW (Roan), and WW (White).
- RW x RR: Offspring are RR (Red) and RW (Roan).

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Summary

- Codominance: Both alleles are expressed equally (e.g., AB blood type).
- Incomplete Dominance: Heterozygotes show an intermediate phenotype (e.g., gray feathers, roan fur).

If you have specific questions about any part of the worksheet, feel free to ask!

Final Answer:
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