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Determining blood type inheritance

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The fathers blood group is AB.

The potential sons blood group is B

mother is blood group A.

1) Draw a mating/ cross diagram to show what the mothers geno type would be in respect to ABO blood group.

2) work out the probability that the child she conceived with the father would have a B blood group, please show full working and clear explanation as i really need to understand this.


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Blood type is based on the antigens expressed on the surface of red blood cells. There are two types of antigens, type A and type B. The absence of either antigen results in the type O blood type (O= no antigen).

Inheritance of blood group is attributed to a combination of 2 of the 3 possible alleles at a single gene. Let's call the locus that controls the blood type I (this is the convention used to represent this locus).

I = the gene

A, B, O = possible alleles

For blood type there are three different alleles that can occur that this locus that correspond to the antigens produced and therefore the blood type. Allele A results in the production of A antigens. Allele B results in the production of B antigens. Allele O results in not antigen produced. These alleles exhibit a co-dominant relationship. Therefore:

1. A person with ...

Solution Summary

Several paragraphs explaining how blood types are inherited and how to determine the blood type from parental genotype. Web references provided.

See Also This Related BrainMass Solution

Genetics Problem - Human Blood Types, Cell Division, Mutations and Genetic Variability

From these 3 alleles, there are 4 blood types (phenotypes): A, B, AB, and O, and there are six genotypes: AA, AO, BB, BO, AB, or OO. This is an example of co-dominance in which both A and B alleles are co-dominant to each other.

Blood types can be used in forensics to determine if blood is from the victim or criminal. Blood types can be used to determine parental source in situation where the father is unknown; however, blood types can only eliminate certain blood types. DNA fingerprinting is a better method that is used often in criminal and parental determination cases.

Punnett squares such as the one shown above are used to determine the probabilities (percentages) for genotypes of offspring given specific genotypes for the parents.

A) In the example above, the Punnett Square represents a cross (mating) between a male (on the left side) with blood type AB, and a female, (top of square), with blood type A, genotype AO.

Answer the following for the cross represented above.

1) What are the possible blood types for the offspring?

2) What are the ratios or percentages for each possible blood type from this cross?

3) What blood type is not possible from this cross?

B) Fill out two Punnett squares for a cross between a male with blood type B and a female with blood type AB. (Note that we do not know if the father is genotype BB or BO from the information given. Thus there are two solutions to the possible cross.)

Set up two Punnett squares and answer the following questions about them.

1) What are the possible blood types for the cross between the type B (BB or BO?) male and AB female?

2) What are the percentages (%) or probabilities for each blood type in the offspring?

3) What blood type(s) would not be possible in a cross between these two parents?

Hint: There are two answers for questions 1 & 2 above and only one for 3.

Turn in the Punnett Squares and your answers to the questions.


Part 2 : Cell division, mutations and genetic variability.

Eukaryotic cells can divide by mitosis or meiosis. In humans, mitosis produces new cells for growth and repair. And, meiosis produces sex cells (gametes), called sperm and eggs. Changes or mutations in genes in sex cells can be inherited by human offspring. Genetic variation in a population of organisms is good; however, sometimes mutations can be harmful or cause genetic disorders.

Briefly, answer the following questions:

How do meiosis and sexual reproduction (fertilization) produce offspring that differ genetically from the parents?

Describe one example of a human disorder that is inherited and also describe the specific inheritance pattern. For this example, pick disorders that result from mutations in DNA or chromosome number rather than examples such as a genetic tendency for a disorder such as cancer.

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