Learn more about genetic diseases in humans, and how the Human Genome Project ha

Question

Learn more about genetic diseases in humans, and how the Human Genome Project has mapped the location of thousands of genes.

Go to the Genetics Home Reference website. http://ghr.nlm.nih.gov/BrowseConditions

1. Choose two genetic diseases to read about. You will answer questions about the two diseases you chose.
2. Click on the link to Chromosomes https://ghr.nlm.nih.gov/chromosome Then choose one chromosome and click on its number. Read the general information about it, as well as the few sample diseases mapped on each.

Then answer the following questions:

2. What is the name of the second disease you selected?  Describe in your own words how the body is affected by this disease.  Summarize the pattern of inheritance for the disease. Is it associated with a single gene or multiple genes? How commonly does it occur? Are particular sexes or ethnic groups affected more commonly?

3. What was the number of the chromosome you selected?  Approximately how many genes are located on this chromosome? Provide one example of a genetic disease caused by an abnormality on this chromosome.

4. If a disease or condition has been linked to a particular gene, does it mean the gene is the sole cause of that disease? What other factors could potentially contribute to the expression of the disease?

Explanation / Answer

1. Selected diseases

i. Phenylketonuria

ii. Sickel cell anemia

2. Sickel cell anemia is caused by a Glu to Val mutation at the 6th amino acid positions of Hemoglobin gene. It results in sickling of RBC if the disease-causing allele is present in homozygous condition. This reduces the carrying capacity of blood to transport gases. This is an autosomal recessive disorder. It is associated with mutations in a single gene. The disease allele shows heterozygote advantage. It provides a selective advantage in malaria prevalent areas. In the US, 1 in 100000 has sickle cell trait. In African Americans, the frequency of sickle cell trait is 1 in 13. It affects both sexes equally.

3. Selected chromosome = Human chromosome 11.

Size = 135 MB

It represents 4.5% of the human genome.

Approximate number of genes present = 1314

Ex: MMP7, ACAT1, and HBB

Diseases associated with Chromosome 11 = Sickel cell disease, Autism, ALbinism, Cystic fibrosis and Beta-thalassemia.

4. An organism's phenotype is the collective outcome of its genotype and the surroundings. Often a mutant genotype can be masked by the environment. For example, good nutrition can extend the lifespan of several genetic disorders. Similarly, the environment can be the sole cause of a disorder. Again, a malnourished kid appears like a diseased kid.

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