Question

Five human matings \((1-5),\) identified by both maternal and paternal phenotypes for \(\mathrm{ABO}\) and \(\mathrm{MN}\) blood-group antigen status, are shown on the left side of the following table: Each mating resulted in one of the five offspring shown in the right-hand column (a-e). Match each offspring with one correct set of parents, using each parental set only once. Is there more than one set of correct answers?

Short answer

Question: Match each offspring with the correct set of parents based on their ABO and MN blood-group antigen status. Offspring: a) B_MM b) O_MN c) A_NN d) A_MM e) B_MN Parental Mating Pairs: Mating 1: IAi x IBi, MM x MN Mating 2: IAIA x IAi, MN x NN Mating 3: IAi x IBi, MM x MN Mating 4: IAi x IBi, MM x MN Mating 5: ii x ii, MN x NN Provide the correct match of offspring to parental mating pairs.

Step-by-step solution

For the ABO blood group, there are three alleles: A, B, and O. The A and B alleles are codominant, meaning that if an individual has both A and B, their blood type is AB. O is a recessive allele, so an individual with OO will have type O blood. For the MN blood group, two alleles are found, M and N, which are also codominant. Thus, if an individual has both, their blood type for the MN antigen status is MN. #Step 2: List possible offspring blood groups for each mating#

Calculate all possible blood types that offspring can have, based on the parents' phenotypes. Here are the possible offspring blood groups for each mating pair: Mating 1: \(\mathrm{ABO}\): IAi, IBi \(\mathrm{MN}\): MM, MN - offspring blood groups: A_MM, A_MN, B_MM, B_MN Mating 2: \(\mathrm{ABO}\): IAIA, IAi \(\mathrm{MN}\): MN, NN - offspring blood groups: A_MN, A_NN Mating 3: \(\mathrm{ABO}\): IAi, IBi \(\mathrm{MN}\): MM, MN - offspring blood groups: A_MM, A_MN, B_MM, B_MN Mating 4: \(\mathrm{ABO}\): IAi, IBi \(\mathrm{MN}\): MM, MN - offspring blood groups: A_MM, A_MN, B_MM, B_MN Mating 5: \(\mathrm{ABO}\): iI, iI \(\mathrm{MN}\): MN, NN - offspring blood groups: O_MN, O_NN #Step 3: Assign offspring to parental pairs#

The order of assigned numbers corresponds to the order of offspring a-e: a) B_MM - can only be produced by Mating 1, 3, or 4. We assign Mating 1 to offspring a. b) O_MN - can only be produced by Mating 5, so we assign Mating 5 to offspring b. c) A_NN - can only be produced by Mating 2, so we assign Mating 2 to offspring c. d) A_MM - can only be produced by Mating 3 or 4, but as Mating 3 is the only available option, we assign it to offspring d. e) B_MN - can only be produced by Mating 4, so we assign Mating 4 to offspring e. #Step 4: Check for multiple correct answers.

Since there are no alternative assignments for each offspring that satisfy the parental phenotypes, there is only one correct set of parent-offspring matches.

Key concepts

ABO blood group system

The ABO blood group system is one of the most important ways to classify human blood types. It is based on the presence of antigens on the surface of red blood cells. These antigens are chemical structures that trigger an immune response if the blood type does not match during a transfusion. The ABO system is determined by three alleles: A, B, and O.

• The A and B alleles are responsible for producing specific antigens on the surface of red blood cells.
• There is a third allele, O, which does not produce any antigens.
• People with an A allele have type A blood, while those with a B allele have type B blood.
• If a person inherits both A and B alleles, their blood type is AB, which carries both antigens.
• Those with two O alleles have type O blood, which lacks these antigens.

Understand that the compatibility of a blood transfusion depends on these antigenic properties. Hence, knowing your ABO blood type is crucial for medical treatments.

alleles

Alleles are different forms of a gene that exist at a specific locus or position on a chromosome. Every person inherits two alleles for each gene, one from each parent. These alleles determine specific traits, such as the blood type in the ABO blood group system.

• Each allele can either be dominant, codominant, or recessive.
• Dominant alleles express their traits even if only one copy is present.
• Recessive alleles require two copies to express their associated traits.
• Codominant alleles, like A and B in the ABO system, express traits simultaneously when both are present.

In human genetics, the interaction between alleles results in diverse phenotypes, like an individual's blood type. Therefore, understanding alleles is key to grasping genetic inheritance and variation.

codominant

Codominance is an interesting genetic principle where two different alleles at a locus are both expressed equally in the phenotype. Unlike simple dominance, where one allele masks the presence of another, codominant alleles showcase both their traits without overshadowing each other.

• In the ABO blood group system, both A and B alleles are codominant.
• When a person receives one of each allele, their blood type is AB, as both antigens are expressed equally on their red blood cells.
• This contrasts with cases where one allele is dominant over another, as seen in other genetic principles.
• Codominance is also observed in the MN blood group system, where both M and N antigens can be present if both alleles are inherited.

Codominance is essential in understanding how genes contribute to a person's overall phenotype and genetic diversity, highlighting the complex nature of hereditary traits.