For a number of human hereditary conditions, genetic testing is available to identify heterozygous carriers. Some heterozygous carrier testing programs are community-based, often as part of an organized effort targeting specific populations in which a disease and carriers of a disease are relatively frequent. For example, carrier genetic testing programs for Tay–Sachs disease target Ashkenazi Jewish populations and sickle cell disease carrier testing programs target African American populations. The testing is usually free or available at minimal cost, the wait time for results is short, and the results are confidential and unavailable to third parties such as insurance companies. Neither the Tay–Sachs nor the sickle cell allele produces serious consequences for heterozygous carriers.

From a genetic perspective, what is the value of the information obtained by genetic testing of the type described?

The accompanying pedigree shows a family in which one child (II-1) has an autosomal recessive condition. On the basis of this fact alone, provide the following information.

What are the probabilities for each of the possible genotypes for II-2, II-3, and II-4?

The accompanying pedigree shows a family in which one child (II-1) has an autosomal recessive condition. On the basis of this fact alone, provide the following information.

Using the same alleles, give the possible genotypes for II-2, II-3, and II-4. <>

The accompanying pedigree shows a family in which one child (II-1) has an autosomal recessive condition. On the basis of this fact alone, provide the following information.

Using A for the dominant allele and a for the recessive allele, give the genotypes for I-1, I-2, and II-1. <>

Select a human hereditary disease or condition you would like to know more about. Using the OMIM website (http://www.ncbi.nlm.nih.gov/omim), search for the disease and prepare a short synopsis of your findings. Include the following information:

Any available information about the population(s) in which the disease is most common.

For a number of human hereditary conditions, genetic testing is available to identify heterozygous carriers. Some heterozygous carrier testing programs are community-based, often as part of an organized effort targeting specific populations in which a disease and carriers of a disease are relatively frequent. For example, carrier genetic testing programs for Tay–Sachs disease target Ashkenazi Jewish populations and sickle cell disease carrier testing programs target African American populations. The testing is usually free or available at minimal cost, the wait time for results is short, and the results are confidential and unavailable to third parties such as insurance companies. Neither the Tay–Sachs nor the sickle cell allele produces serious consequences for heterozygous carriers.

Do you personally think you would participate in the kind of carrier genetic testing described if you were a member of a population targeted for such testing?

For a number of human hereditary conditions, genetic testing is available to identify heterozygous carriers. Some heterozygous carrier testing programs are community-based, often as part of an organized effort targeting specific populations in which a disease and carriers of a disease are relatively frequent. For example, carrier genetic testing programs for Tay–Sachs disease target Ashkenazi Jewish populations and sickle cell disease carrier testing programs target African American populations. The testing is usually free or available at minimal cost, the wait time for results is short, and the results are confidential and unavailable to third parties such as insurance companies. Neither the Tay–Sachs nor the sickle cell allele produces serious consequences for heterozygous carriers.

In a broader sense, what is the value of a community-based effort targeting specific populations for selected diseases?

In humans, the ability to bend the thumb back beyond vertical is called hitchhiker's thumb and is dominant to the inability to do so (OMIM 274200; see Problem 41). Also, the presence of attached earlobes is recessive to unattached earlobes (OMIM 128900).

Using all available and willing members of your family, or members of another family if yours is not easily accessible, trace the transmission of both traits in a pedigree. Use allelic symbols H and h for the thumb and E and e for earlobes, and identify the genotypes for each family member as completely as possible. Bring the pedigree back to share with your group.

In humans, the ability to bend the thumb back beyond vertical is called hitchhiker's thumb and is dominant to the inability to do so (OMIM 274200; see Problem 41). Also, the presence of attached earlobes is recessive to unattached earlobes (OMIM 128900).

Check your own phenotype and those of several friends or classmates.