Sickle Cell Disease
Directions:
For this assignment (Part 2 of the Case Report), write a 1,000 word paper incorporating
genetics information learned from assigned readings in Topics 1-3. Include the following:
- Describe if chromosomal analysis is/was indicated.
- Detail the causes of the disorder.
- Describe the disorder in terms of its origin as either a single gene inheritance, or as a
complex inheritance and considerations for practice and patient education. - Analyze the gene mutation of the disease, as well as whether it is acquired or inherited,
and how the mutation occurs.
Sickle Cell Disease
Introduction
Sickle cell disease is among the fatal disorders that are mostly inherited. Approximately
100,000 people in America have the disorder. It is most prevalent among people of the African
origin. Approximately one person among 12 African Americans has the disease and 0ne among
100 Hispanic Americans have the sickle cell trait meaning that they are carriers. This paper
discusses various aspects of sickle cell anemia detailing its causes and the way gene mutation
leads to the disease.
Chromosomal Analysis is/was indicated
The chromosomal analysis involves a study of some several general structures of 46
chromosomes. The process involves counting and checking the chromosomes from the cells to
ensure that they contain the right amount of chromosomes. The structure of the chromosomes is
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also examined to make sure that it is normal shaped. Chromosomal analysis cannot apply to the
study of sickle cell anemia because it is impossible to detect single gene condition. The
chromosomal analysis, therefore, not indicated in the disorder because it results from the
mutation of the hemoglobin-Beta gene found in chromosome 11, which is a tinny deletion to be
detected by the process (Ware et al. 2017). Hemoglobin is responsible for transporting oxygen
from the lungs to other body parts. Regular hemoglobin (hemoglobin-A) are round shaped and
move in the blood vessels smoothly transporting oxygen to the body parts, but the abnormal
hemoglobin molecules (hemoglobins) assume a sickle shape (Serjeant, 2013). Thus, they clog
together forming extended rod-like arrangements that make the erythrocytes to be rigid. The
sickle shape makes the erythrocytes to cause blockages hence injuring essential body tissues and
organs. When addressing sickle cell disease, it is critical to consider chromosomes, as the genes
are part of chromosomes.
Causes of the Sickle cell Disorder
Typically, sickle cell anemia occurs as a result of mutation of the genes that form
hemoglobin (Rees, Williams, & Gladwin, 2010). Hemoglobin is a compound rich in iron that
gives blood the red color, and it is responsible for allowing the erythrocytes to carry oxygen from
the alveolus in the lungs to other body tissues and organs. The sickle cell gene is inherited from
one generation to another in an inheritance pattern referred to as autosomal recessive inheritance.
It implies that both parents must pass the abnormal form of the gene for the child to be affected.
In situations only one parent passes the gene to the child, it means that the child will only have
the sickle cell trait but will not be affected by the disorder. People with normal and defective
hemoglobin will form both normal hemoglobin and some sickle cell hemoglobin, but they will
not have symptoms (Ware et al., 2017). They will become carriers of the disorder meaning they
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can pass the traits to their children. The primary cause of the disease is gene mutation and not
any other cause.
Origin of Sickle cell Anemia
Sickle cell disorder originates from a mutation in the HBB gene (Rees, Williams, &
Gladwin, 2010). The genetic changes that lead to the disorder can be described as follows.
Hemoglobin compound contains four proteins subunits. One of the subunits is called alpha-
globin, and the other is called the beta-globin. The HBB gene has the responsibility of informing
the body to form beta-globin. As a result, different kinds of beta-globin results from the mutation
in the HBB gene and a specific HBB gene mutation may produce a defective beta-globin called
hemoglobin-S (HbS). Also, other versions of mutation in HBB gene can create abnormal types of
beta-globin including hemoglobin C (HBC) and Hemoglobin E (HbE). Therefore, individuals
with the sickle cell disease have at least one subunit of beta-globin replaced with hemoglobin S.
When Hemoglobin S takes the place of beta-globin, a person suffers from sickle cell anemia, and
the symptoms of the disease can be detected. Defective types of beta-globin can potentially
affect the erythrocytes causing them to take sickle shape making them die prematurely leading to
anemia (Yawn et al., 2014). Sometimes, the sickle-shaped red blood cells can stick to the blood
vessels causing severe medical complications.
The disease is characterized by the single cell gene mutation, which tends to carry an
abnormal gene which has a sickle cell trait. The abnormal gene has one normal β chain gene
known as β A and one abnormal β chain gene, β S as well as a single gene. These cells have two
types of hemoglobin, which are basically the normal α 2 β 2 together with the sickle cell α 2 β 2 s . In
this case, the situation is known as the sickle cell trait. Individuals who have inherited the β S gene
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from both the father and the mother can only make the cell hemoglobin and this means that their
hemoglobin contains the sickle cell diseases with a single-cell form of inheritance.
Gene Mutation of the Disease
Gene mutation is the main cause of sickle cell anemia. It is a disease that can only be
inherited and not acquired. Mutation in the gene responsible for the formation of hemoglobin
causes the disease and individuals with two sets of the sickle cell can manifest the symptoms of
the disorder. On the other hand, people with an only single copy of sickle cell do not manifest the
symptoms of the disease but can pass the gene to their offspring. The mutations that result in
sickle cell anemia have been studied extensively. The effects of mutation can be traced from the
DNA to the entire organism. Although a person with a single copy of sickle cell does not have
the disease, it still affects her cells, and her proteins (Hoban et al. 2015). The figure below shows
that effects of mutation at the DNA level and the protein level.
(The Understanding Evolution team (n.d)
Mutation in HBB gene is a series of causation. The changes happening in the DNA level
continue to occur until the whole organism is affected eventually (Ware et al. 2017). This shows
that a single mutation can have a large effect on the organism and its offspring. The main fact is
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that even if the mutation is a mall or large, its effects can spread gradually until the whole
organism is affected.
Conclusion
It can be concluded that sickle cell disease is among the commonly inherited diseases. It
affects people with two copies of the defective beta-globin. The diseases if fatal and can lead to
early mortality among the affected people. Sickle cell anemia is purely a disease of gene
mutations.
References
Hoban, M. D., Cost, G. J., Mendel, M. C., Romero, Z., Kaufman, M. L., Joglekar, A. V., &
Cooper, A. R. (2015). Correction of the sickle cell disease mutation in human
hematopoietic stem/progenitor cells. Blood, 125(17), 2597-2604.
Rees, D. C., Williams, T. N., & Gladwin, M. T. (2010). Sickle-cell disease. The
Lancet, 376(9757), 2018-2031.
Serjeant, G. R. (2013). The natural history of sickle cell disease. Cold Spring Harbor
perspectives in medicine, 3(10), a011783.
The Understanding Evolution team (n.d) DNA and Mutations.