Table of contents
- 1. Introduction to Genetics51m
- 2. Mendel's Laws of Inheritance3h 37m
- 3. Extensions to Mendelian Inheritance2h 41m
- 4. Genetic Mapping and Linkage2h 28m
- 5. Genetics of Bacteria and Viruses1h 21m
- 6. Chromosomal Variation1h 48m
- 7. DNA and Chromosome Structure56m
- 8. DNA Replication1h 10m
- 9. Mitosis and Meiosis1h 34m
- 10. Transcription1h 0m
- 11. Translation58m
- 12. Gene Regulation in Prokaryotes1h 19m
- 13. Gene Regulation in Eukaryotes44m
- 14. Genetic Control of Development44m
- 15. Genomes and Genomics1h 50m
- 16. Transposable Elements47m
- 17. Mutation, Repair, and Recombination1h 6m
- 18. Molecular Genetic Tools19m
- 19. Cancer Genetics29m
- 20. Quantitative Genetics1h 26m
- 21. Population Genetics50m
- 22. Evolutionary Genetics29m
3. Extensions to Mendelian Inheritance
Variations of Dominance
Problem 7
Textbook Question
With regard to the ABO blood types in humans, determine the genotype of the male parent and female parent shown here:
Male parent: Blood type B; mother type O
Female parent: Blood type A; father type B
Predict the blood types of the offspring that this couple may have and the expected proportion of each.

1
Determine the possible genotypes of the male parent. Since the male parent has blood type B and his mother has blood type O, his genotype must be heterozygous (IBi), as he inherited the 'i' allele from his mother and the 'IB' allele from his father.
Determine the possible genotypes of the female parent. Since the female parent has blood type A and her father has blood type B, her genotype must be heterozygous (IAi), as she inherited the 'i' allele from her father and the 'IA' allele from her mother.
Set up a Punnett square to predict the offspring's blood types. Place the male parent's alleles (IB and i) on one axis and the female parent's alleles (IA and i) on the other axis. Fill in the Punnett square by combining the alleles from each parent.
Analyze the Punnett square to determine the possible genotypes of the offspring. The combinations will be: IAIB (blood type AB), IAi (blood type A), IBi (blood type B), and ii (blood type O).
Calculate the expected proportions of each blood type. Since each genotype has an equal probability of occurring, the expected proportions are 25% for each blood type: AB, A, B, and O.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
ABO Blood Group System
The ABO blood group system classifies human blood into four main types: A, B, AB, and O, based on the presence or absence of antigens on the surface of red blood cells. Blood type A has A antigens, type B has B antigens, type AB has both, and type O has neither. This classification is crucial for understanding inheritance patterns and predicting offspring blood types.
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Genotype and Phenotype
Genotype refers to the genetic makeup of an individual, while phenotype is the observable expression of that genotype. For blood types, the genotype can be homozygous (e.g., AA or BB) or heterozygous (e.g., AO or BO). Understanding the relationship between genotype and phenotype is essential for predicting the blood types of offspring based on parental genotypes.
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Punnett Square
A Punnett square is a diagram used to predict the genetic outcomes of a cross between two individuals. It allows for the visualization of how alleles from each parent combine to form potential genotypes in offspring. By filling out a Punnett square with the parents' genotypes, one can determine the expected proportions of each blood type among the offspring.
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Related Practice
Textbook Question
In mice, a short-tailed mutant was discovered. When it was crossed to a normal long-tailed mouse, 4 offspring were short-tailed and 3 were long-tailed. Two short-tailed mice from the F1 generation were selected and crossed. They produced 6 short-tailed and 3 long-tailed mice. These genetic experiments were repeated three times with approximately the same results. What genetic ratios are illustrated? Hypothesize the mode of inheritance and diagram the crosses.
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