Untitled

Genetics Practice #2: Incomplete, Co-Dom and Blood Types

I. Codominance and Incomplete Dominance in Offspring

A. Roan Cattle and Hair Color

• Phenomenon: Roan cattle exhibit codominance for hair color.
• Alleles involved: Red hair and white hair alleles.
• Question: Offspring appearance when crossing a red bull with a white cow.   - Expected Outcome: Offspring would display both red and white hairs (roan).

B. Chicken Feather Color

• Phenomenon: Breed of chicken that shows codominance for feather color.
• Alleles involved: One allele for black feathers and another for white feathers.
• Question: Possible feather colors when two speckled chickens mate.   - Expected Outcomes: Possible colors are black, white, and speckled (both colors visible).

C. Flower Color in Four O'clock Plants

• Phenomenon: Incomplete dominance observed where heterozygous individuals appear pink.
• Parental plants needed for pink-flowered offspring:   - Parent Plant Colors: One plant must be red (RR) and the other white (WW) to produce pink (RW) flowers.

D. Goat Color Inheritance

1. Inheritance Type:
      - Answer: Codominance.
2. Justification:Different colors (black and white) appear in the offspring.
3. Genotype of Partner: Must include at least one black and one white allele.
      - Example Cross: If the Grey goat's genotype is (GB), the partner can be (BB) or (WW). Example cross:
       ext{GB (grey) x BB (black)} \ ext{Offspring: 50% grey (GB), 50% black (BB)}

II. Blood Type "Multiple Allele" Problems

A. Possible Genotypes for Blood Types

1. Type O: Genotype - $OO$
2. Type A: Genotypes - $AA, AO$
3. Type B: Genotypes - $BB, BO$
4. Type AB: Genotype - $AB$

B. Children Blood Types from AB Parents

1. Parent genotypes: Both parents have AB blood.
2. Possible Blood Types: Children can be A (50%), B (50%), or AB (100%).    - Proportions: 25% A, 25% B, 50% AB.

C. Type B and Type O Parentage

1. Father's genotype: BB (Type B).
2. Mother's genotype: OO (Type O).
3. Children's Blood Types: All offspring will have B (BO) blood type.

D. Crossing Type A (AO) and Type B (BO)

1. Parent Genotypes: Mother - $AO$; Father - $BO$
2. Possible Blood Types in Children: A (50%), B (50%), AB (25%).

E. Mating Between A Woman with Type A and a Man with Type AB

1. Woman’s Genotypes: AO or AA.
2. Man’s Genotype: AB.
3. Possible Outcomes: Children can have A, B, or AB blood types.    - Cross Illustration for AO:
   $ext{AO (mother) x AB (father)}$    - Possible offspring: A (50%), B (25%), AB (25%).

F. A Man with Type AB Blood and a Woman with Type O Blood

1. Blood Types of Children: Possible blood type among children can be A (50%) and B (50%); C cannot be O, which means O child is adopted.

G. Type A (unknown genotype) and Type O Couple

1. Possible Blood Types: A (50%), O (50%).    - Cross:
   $ext{AO (A) x OO (O)}$

H. Type B (unknown genotype) and Type A (unknown genotype) Couple

1. Parent Types: B (BB or BO) and A (AA or AO).
2. Possible Blood Types for Offspring: A, B, AB, O.    - Multiple Crosses Required:
      - For BB x AA: Outcomes are B (100%).    - For BO x AO: Outcomes are A, B, O (75%).

III. Objectives and Topics on Genetics

A. Objectives overview

1. Recognize inheritance patterns: Incomplete Dominance, Codominance, Multiple Alleles, Sex Linked Traits, Polygenic Traits.
2. Use Punnett squares to answer inheritance questions.
3. Describe gene linkage and crossing over in mapping chromosomes.
4. Describe the human karyotype.
5. Recognize inheritance patterns of genetic disorders.
6. Familiarity with genetic disorders and inheritance methods.
7. Applications of genetics today.
8. Discuss moral and ethical implications of genetic practices.

IV. Guided Notes and Key Concepts

A. Genetic Disorders

1. Recessive Alleles Advantage: Carriage of genetic disorders by recessive alleles may provide benefits through heterozygote advantages (e.g., sickle cell trait providing malaria resistance).
2. Disadvantages: Carrier status might lead to the expression of harmful recessive traits.
3. Diseases Caused by Recessive Alleles: Cystic fibrosis, Tay-Sachs disease, Sickle cell anemia, Phenylketonuria (PKU).
4. Conditions Caused by Dominant Alleles: Huntington’s Disease, Marfan Syndrome, Achondroplasia.
5. Codominance Example: AB blood type exhibits codominance.
6. Definition of Pedigree: A chart that depicts family relationships and the inheritance of traits and genetic conditions.
7. Utility of Pedigrees: Useful in tracing inheritance patterns for traits and understanding familial genetic diseases.

B. Inheritance Patterns Explained

1. Incomplete Dominance vs. Simple Dominance: In incomplete dominance, heterozygous individuals display a blend of phenotypes instead of one allele dominating.
2. Recognition of Incomplete Dominance Crosses: Look for phenotypic ratios indicating blending in the offspring.
3. Heterozygous Genotype Phenotype: In incomplete dominance, it presents as an intermediate phenotype (e.g., pink flower).
4. Punnett Square for Four O'clock Flowers: Crossing pink four o'clock flowers:    - ext{RR x WW} \ ext{Offspring: 25% RR; 50% RW (pink); 25% WW}
5. Codominance vs. Simple Dominance: Both alleles contribute equally to the phenotype in codominance.
6. Recognition of Codominance Crosses: Both phenotypes must be observable in heterozygotes.
7. Heterozygous Genotype in Codominance: Exhibits traits from both alleles.
8. Punnett Square for Roan Cattle:
       ext{RR x WW} \ ext{Offspring: 25% RR (red); 50% RW (roan); 25% WW (white)}
9. Multiple Alleles vs. Simple Dominance: More than two alleles control a trait in multiple alleles, contrary to simple dominance.
10. Recognition of Multiple Alleles Crosses: Expect more genotype phenotypes due to increased allele options.
11. Example of Multiple Alleles Trait: Blood type inheritance involving A, B, O alleles.
12. Blood Type Inheritance Pattern: Types A and B exhibit codominance while O shows simple recessive.
13. Relationship between Blood Type Alleles: A and B are codominant to each other but both are dominant to O allele, leading to four possible phenotypes.

V. Incomplete Dominance and Codominance Crosses

1. Example of Incomplete Dominance in Cats:    - Genotypes: Long tail (LL), No tail (NN), Short tail (heterozygous).    - Predicted Crosses:      - Long Tail (LL) x No Tail (NN) results in all Short Tail (LN).      - Short Tail (LN) x Short Tail (LN) yields 25% LL, 50%LN, 25%NN.
2. Example of Codominance in Dogs:    - Genotypes: Black dogs (BB), Tan dogs (TT), Spotted dogs (BT).    - Possible Outcomes with Spotted Dog Cross (BT):
        - With Tan Dog (TT): 50% BT (Spotted), 50% TT (Tan).      - With Another Spotted Dog (BT): 25% BB (Black), 50% BT (Spotted), 25% TT (Tan).

VI. Probability and Explanation for Blood Type Inheritance

1. Phenotypes Calculation for Blood Type Crosses: Calculate outcomes of crosses and explain:    - Type O Parents can only yield Type O offspring.    - Recursive Instructions: Use Punnett squares for each cross and deduce possible offspring blood types.

VII. Analysis of Blood Type Cases

1. Mix-Up Investigation: Analyze blood types in family scenarios to deduce relationships. Use blood type inheritance rules to ascertain biological relationships based on genotypes observed in offspring.
2. Example Case: Examine how John and Mary’s children can have diverse blood types based on their genotypes.