In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure.
Chromosomes are not visible in the cell’s nucleus—not even under a microscope—when the cell is not dividing. However, the DNA that makes up chromosomes becomes more tightly packed during cell division and is then visible under a microscope. Most of what researchers know about chromosomes was learned by observing chromosomes during cell division.
Each chromosome has a constriction point called the centromere, which divides the chromosome into two sections, or “arms.” The short arm of the chromosome is labeled the “p arm.” The long arm of the chromosome is labeled the “q arm.” The location of the centromere on each chromosome gives the chromosome its characteristic shape, and can be used to help describe the location of specic genes.
Fetal Hemoglobin (Hgb.F)
A kind of hemoglobin usually present during fetal (intrauterine) life, which has a different chemical structure from normal adult hemoglobin. After birth, the fetal hemoglobin in the red blood cells is gradually replaced by the adult type of hemoglobin, this process is usually complete during the rst 6 months of life.
A Gene is the ultimate unit of inheritance, and is carried by the chromosome. Genes determine our various characteristics such as hair texture, skin color, height, shape of nose, lips, etc., including the kind of hemoglobin in the red blood cells. Genes, which are made up of DNA, act as instructions to make molecules called proteins. In humans, genes vary in size from a few hundred DNA bases to more than 2 million bases. The Human Genome Project has estimated that humans have between 20,000 and 25,000 genes.
In genetic counseling, specially-trained professionals help people learn about genetic conditions, find out their chances of being affected by or having a child or other family member with a genetic condition, and make informed decisions about testing and treatment. This communication process between health care provider and client, emphasizes providing accurate and up-to-date information about a genetic disorder in a sensitive and supportive, non-directive manner.
Genetic mutation is a permanent alteration in the DNA (a change in hereditary characteristics due to a permanent change in a gene) sequence that makes up a gene, such that the sequence differs from what is found in most people. Mutations range in size; they can affect anywhere from a single DNA building block (base pair) to a large segment of a chromosome that includes multiple genes.
The chemical substance (an iron containing protein) of the red blood cell which carries oxygen to the tissues, and gives the cell its red color.
A laboratory technique to determine the type of hemoglobin the individual has. When you pass an electric charge through a solution of hemoglobin, distinct hemoglobins move different distances, depending on their composition. This technique differentiates between usual hemoglobin (A), sickle hemoglobin (S) and many other different kinds of hemoglobin (such as C, D, E, etc.).
To receive certain dened characteristics from a parent by transmission of the genes in the egg and sperm.
Red Blood Cell
Red blood cells play an important role in your health by carrying fresh oxygen throughout the body. Red blood cells are round with a attish, indented center, like doughnuts without a hole. These cell, which contain hemoglobin, circulate throughout the body. Your healthcare provider can check on the size, shape, and health of your red blood cells using tests, such as the complete blood count screening.
Sickle Cell Anemia
An inherited disorder of the red blood cells in which the hemoglobin (the red oxygen carrying pigment of the cell) is different from the usual type. This unusual hemoglobin results in the production of unusually shaped cells, which do not survive the usual length of time in the blood circulation. Thus, anemia results. Sickle cell anemia is the result of the inheritance of the gene for sickle hemoglobin (S) from both parents.
Sickle Cell Disease
The term sickle cell disease (SCD) describes a group of inherited red blood cell disorders. People with SCD have abnormal hemoglobin, called hemoglobin S or sickle hemoglobin, in their red blood cells. People who have SCD inherit two abnormal hemoglobin genes, one from each parent. In all forms of SCD, at least one of the two abnormal genes causes a person’s body to make hemoglobin S. When a person has two hemoglobin S genes, Hemoglobin SS, the disease is called sickle cell anemia. This is the most common and often most severe kind of SCD. Other forms of Sickle Cell Disease include SC, CC, S Beta Zero thalassemia, S Beta+ thalassemia, SD, and SE.
Sickle Cell Trait
The inheritance of one gene for the usual hemoglobin (A) and one gene for sickle hemoglobin (S). A person who has sickle cell trait (AS) is a carrier of the sickle gene, does not have the disease, does not have painful episodes, and is generally not affected by the sickle hemoglobin.
An inherited disorder of a gene in the red blood cells which results in the impaired ability to produce hemoglobin.
In 1989, there where 489 unusual hemoglobins identied. The unusual hemoglobins most commonly seen (frequency in population greater than 1%) are hemoglobins: S (sickle), C, Thal, E, and D (Punjab).