Q1a. What would be the genotype of a person with type B blood who has a parent with type O blood?

Background

Topic: Mendelian Genetics, Multiple Alleles, and Codominance

This question tests your understanding of how the ABO blood group system is inherited, specifically how genotypes determine blood types and how parental genotypes influence offspring genotypes.

Key Terms and Concepts:

• Allele: Different forms of a gene (e.g., IA, IB, i).

• Codominance: Both alleles are expressed equally (e.g., IAIB).

• Recessive: An allele that is masked by a dominant allele (e.g., i is recessive to both IA and IB).

• Genotype: The genetic makeup (combination of alleles) of an individual.

• Phenotype: The observable trait (e.g., blood type B).

Step-by-Step Guidance

1. Recall that type B blood can result from two possible genotypes: (homozygous) or (heterozygous).

2. Type O blood is always genotype (homozygous recessive), so a parent with type O can only pass on the allele.

3. For the child to have type B blood, they must have at least one allele (from the other parent) and one allele (from the type O parent).

Try solving on your own before revealing the answer!

Q1b. Describe the phenotype of someone whose genotype is IAIB. Don’t just list what their blood type would be—describe what the surface of their red blood cells would look like.

Background

Topic: Codominance and Blood Group Antigens

This question tests your understanding of how codominant alleles are expressed in the phenotype, specifically in the context of the ABO blood group system.

Key Terms and Concepts:

• Codominance: Both alleles are fully expressed in the phenotype.

• Antigen: A molecule on the surface of red blood cells that determines blood type.

• IA: Codes for type A antigen.

• IB: Codes for type B antigen.

Step-by-Step Guidance

1. Recognize that the genotype means the individual has one allele for type A antigen and one for type B antigen.

2. Because and are codominant, both antigens will be expressed on the surface of the red blood cells.

3. Think about what this means for the cell surface: both types of antigens will be present, not just one or the other.

Try describing the phenotype in your own words before revealing the answer!

Q2a. Draw a Punnett square depicting a cross between a GgSs plant and a ggSs plant.

Background

Topic: Dihybrid Crosses and Punnett Squares

This question tests your ability to set up and analyze a dihybrid cross, which involves two genes (leaf color and leaf pattern) each with two alleles.

Key Terms and Concepts:

• Dihybrid Cross: A cross between individuals heterozygous for two traits.

• Punnett Square: A diagram used to predict the genotypes of offspring from a genetic cross.

• Alleles: G (green), g (yellow), S (striped), s (solid).

Step-by-Step Guidance

1. Determine all possible gametes for each parent:

   • GgSs parent can produce: GS, Gs, gS, gs

   • ggSs parent can produce: gS, gs

2. Set up a Punnett square with the GgSs parent's gametes on one axis and the ggSs parent's gametes on the other axis.

3. Fill in each box by combining the alleles from the corresponding gametes to show the possible genotypes of the offspring.

4. Be sure to keep track of both genes (color and pattern) in each genotype.

Try drawing and filling in the Punnett square before checking the completed version!

Q2b. What is the phenotype ratio of the offspring from this cross?

Background

Topic: Phenotypic Ratios in Dihybrid Crosses

This question tests your ability to interpret the results of a Punnett square and determine the ratio of observable traits among the offspring.

Key Terms and Concepts:

• Phenotype: Observable traits (e.g., green striped, green solid, yellow striped, yellow solid).

• Genotype: The genetic makeup that determines phenotype.

• Ratio: The proportion of each phenotype among the offspring.

Step-by-Step Guidance

1. From your completed Punnett square, count the number of each genotype that corresponds to each phenotype.

2. Recall the dominance relationships: G (green) is dominant to g (yellow); S (striped) is dominant to s (solid).

3. Group the genotypes into their corresponding phenotypes (e.g., any genotype with at least one G and one S will be green striped).

4. Write out the ratio of each phenotype based on your counts.

Try calculating the phenotype ratio before revealing the answer!