Other patterns of inheritance

Explain what codominance is and give a human example in which two alleles are expressed simultaneously.

Explain what incomplete dominance is and describe which phenotype appears when crossing a red-flowered plant with a white-flowered plant if the trait follows this pattern.

The alleles $I^A$, $I^B$ and $i$ are involved in blood groups. State which genotypes correspond to blood groups A, B, AB and O.

A person with blood group AB and a person with blood group O have a child. State the possible blood groups of the child and their probabilities, excluding each parent's blood group from the possibilities.

In four o'clock plants, flower colour shows incomplete dominance: red (RR), pink (Rr) and white (rr). Complete the Punnett square in the diagram, where two pink-flowered plants are crossed, and state the genotypic and phenotypic ratios of the offspring.

Explain the difference between codominance and incomplete dominance, and give an example of each one.

In humans, sex is determined chromosomally: females are XX and males are XY. Explain, using the corresponding cross, why the probability of having a son or a daughter is equal (1:1 ratio) and which parent provides the chromosome that determines the sex of the offspring.

A couple attends a genetic counseling consultation: the man has normal vision and so does the woman, but she is concerned because her maternal grandfather was color-blind (her maternal grandmother and her father had normal vision and had no family history). The man claims there is nothing to worry about, stating: "Since I am not color-blind, it is impossible for us to have a color-blind daughter or son."

1. a) Reasonably deduce the probability that the woman is a carrier based on the data from her maternal family.
2. b) Refute or validate the man's claim using genetic arguments for daughters and sons separately, showing the possible crosses.
3. c) Calculate the final probability that the first child born to this couple is a color-blind male.

Explain what it means for a gene to be linked to the X chromosome and reason why men (XY) have only one allele for those genes, while women (XX) have two.

In Andalusian hens, plumage colour shows incomplete dominance: BB is black, Bb is blue and bb is white. Cross two blue hens and state the expected genotypic and phenotypic ratios in the chicks.

A medical emergency occurs in a hospital and a patient with blood type 0 urgently needs a transfusion. When testing their biological parents, it is found that the father is type A and the mother is type B. A student intern claims that there must be an error in parentage, arguing that "two parents with dominant A and B antigens can never produce a type 0 child, who lacks both antigens."

1. a) Refute the student's statement by deducing the exact genotypes that the parents must have, and represent the cross that demonstrates the genetic viability of the patient's birth.
2. b) If this same couple has more offspring, predict the expected phenotypic percentages for each blood type.
3. c) Justify whether any of the future siblings could donate red blood cells to the type 0 patient.