· A missense mutation is when the change of a single base pair causes the substitution of a different amino acid in the resulting protein. This amino acid substitution may have no effect, or it may render the protein nonfunctional.
· An example of a Missense Mutation would The replacement of A by T at the 17th nucleotide of the gene for the beta chain of hemoglobin changes the codon GAG (for glutamic acid) to GTG (which encodes valine). Thus the 6th amino acid in the chain becomes valine instead of glutamic acid.
· One potential genetic disorder caused by this mutation would be sickle cell disease
Sickle Cell Disease
· Sickle Cell Disease is a severe hereditary form of anemia in which a mutated form of hemoglobin distorts the red blood cells into a crescent shape at low oxygen levels. It is most common among those of African descent.
· Symptoms of Sickle cell Disease can be any of these listed. Anemia, fatigue, chronic pain, shortness of breath and/or dizziness, headaches, coldness in hands or feet, pale skin due to anemia, Jaundice, or yellow eyes and skin, chest pain, and leg ulcers that do not heal.
· The goals of treating sickle cell disease are to prevent or relieve pain; prevent infections, organ damage, and strokes; treat anemia; and control complications. Those with more severe sickle cell anemia may benefit from daily administration of a medicine called hydroxyurea. This medicine may help reduce the number of painful crises. Bacterial infections can be a major complication of sickle cell disease, but often they can be prevented or treated by getting daily doses of penicillin and all routine vaccines. Blood transfusions are commonly used to treat worsening anemia and sickle cell complications as well.
· A simple blood test, done at any time during a person's lifespan, can detect whether he or she has sickle hemoglobin. However, early diagnosis is very important.
· A nonsense mutation is a single base pair substitution that prematurely codes for a stop in amino acid translation (stop codon)
· An example of a nonsense mutation would be the nucleotide cytosine being replaced by thymine in the DNA code, signaling the cell to shorten the protein.
· A potential genetic disorder of a nonsense mutation would be cystic fibrosis.
· Cystic fibrosis is a serious genetic condition that causes severe damage to the respiratory and digestive systems. This damage often results from a buildup of thick, sticky mucus in the organs.
· The symptoms of cystic fibrosis can vary depending on the person and the severity of the condition. Coughing up thick mucus, Wheezing or shortness of breath, Getting sinus infections, bronchitis, or pneumonia often, Growths, called polyps, in the nose, Bulky, oily, or foul-smelling stool, Too much gas, constipation, or stomach pain, Weight loss or failure to gain weight, Low bone density, Wide, rounded fingertips and toes, called clubbing
· Although there’s no cure for cystic fibrosis, there are various treatments available that may help relieve symptoms and reduce the risk of complications. Examples of these would be medications, surgical procedures, and basic home care.
· In the United States, all newborns are screened for cystic fibrosis. Doctors use a genetic test or blood test to check for signs of the disease. Some tests used to diagnose cystic fibrosis are the IRT test, Seat Chloride Test, Sputum Test, Chest X-rays, CT scans, and PFTs (Pulmonary Function Tests).
This is an x-ray of a person with cystic fibrosis in the lungs.
A diagram of a baby with cleft palate and a baby with a cleft lip and palate
The human brain, showing the impact of HD on brain structure in the basal ganglia region of a person with HD (top) and a normal brain (bottom).
· A silent mutation is an alteration in a DNA sequence that does not result in an amino acid change in a polypeptide.
· An example of a Silent Mutation would be the DNA codons CAA, CAG, CAT, and CAC all code for the amino acid valine. If a strand of DNA undergoes a point mutation in the codon CAA that changes it to CAG, it would still code for valine
· Although Silent mutations are linked to almost fifty diseases on example would be diabetes.
· Diabetes mellitus is a group of metabolic diseases characterized by high blood sugar (glucose) levels that result from defects in insulin secretion, or its action, or both.
· The following symptoms of diabetes are typical. However, some people with type 2 diabetes have symptoms so mild that they go unnoticed. Urinating often, feeling very thirsty, feeling very hungry- even though you are eating, extreme fatigue, blurry vision, cuts/bruises that are slow to heal, weight loss- even though you are eating more (type 1), tingling, pain, or numbness in the hands/feet (type 2).
· Treatment for diabetes requires keeping close watch over your blood sugar levels (and keeping them at a goal set by your doctor) with a combination of medications, exercise, and diet.
· Doctors take a range of tests in order to diagnose diabetes such as a fasting glucose test, an oral glucose tolerance test (OGTT), or the A1C test.
· Insertion is a type of mutation involving the addition of genetic material. An insertion mutation can be small, involving a single extra DNA base pair, or large, involving a piece of a chromosome.
· Huntington's disease and the fragile X syndrome are examples of insertion mutation wherein trinucleotide repeats are inserted into the DNA sequence leading to these diseases.
· A genetic disorder caused by Insertion Mutations would be Huntington’s Disease.
· Huntington disease is a progressive brain disorder that causes uncontrolled movements, emotional problems, and loss of thinking ability (cognition).
· Throughout the stages of Huntington's disease there are different symptoms. Common symptoms in the early stages include; slight change in coordination, affecting balance or making you more clumsy, fidgety movements that you can’t control, slowing or stiffness, trouble thinking through problems, depression or irritability.
· Treatment for Huntington's disease include medications to help with fidgety movements, speech or language therapy, occupational or physical therapy, nutritional support, and exercise.
· A diagnosis of Huntington's disease is based primarily on your answers to questions, a general physical exam, a review of your family medical history, and neurological and psychiatric examinations.
· Deletion is a type of mutation involving the loss of genetic material. It can be small, involving a single missing DNA base pair, or large, involving a piece of a chromosome.
· In this example, one nucleotide (adenine) is deleted from the DNA code, changing the amino acid sequence that follows.
· A genetic disorder that is caused by Deletion mutations would be cleft palate.
· Cleft lip and cleft palate are facial and oral malformations that occur very early in pregnancy, while the baby is developing inside the mother. Clefting results when there is not enough tissue in the mouth or lip area, and the tissue that is available does not join together properly.
· Symptoms from cleft palate include Difficulty with feedings, difficulty swallowing, with potential for liquids or foods to come out the nose, nasal speaking voice, chronic ear infections
· The goals of treatment for cleft lip and cleft palate are to improve the child's ability to eat, speak and hear normally and to achieve a normal facial appearance.
· It’s possible for cleft palate and lip to be diagnosed while your baby is still in the womb through the use of an ultrasound.
Splice Site Mutation
· A splice site mutation is a genetic mutation that inserts, deletes or changes a number of nucleotides in the specific site at which splicing takes place during the processing of precursor messenger RNA into mature messenger RNA.
· An example of Splicing Site mutations would be the splicing change that can result from mutations within intronic or exonic splicing elements within the genes relevant to cancer, such as oncogenes or tumor suppressors
· A potential genetic disorder caused by Splice Site Mutations would be Familial isolated growth hormone deficiency type II (IGHD II).
Isolated growth hormone deficiency
· Growth hormone deficiency is a disorder that involves the pituitary gland (a small gland located at the base of the brain). This gland produces growth hormone and other hormones (chemical messengers of the body). When it does not produce enough growth hormone, growth will be slower than normal.
· Symptoms of Isolated growth hormone deficiency include children with GHD are shorter than their peers, GHD delays puberty, reduced bone strength, tiredness and lack of stamina, sensitivity to hot and cold temperatures, depression, lack of concentration, poor memory, bouts of anxiety or emotional distress.
· Growth hormone deficiency can be treated with growth hormone replacement therapy. A drug called somatropin or growth hormone Nutropin, Genotropin,Norditropin, Saizen, Humatrope, Tev-tropin, Omnitrope) is injected into the fat underneath the skin.
· For children, the doctor will ask about the child's medical history. If the child's height and weight have been plotted on a growth chart, the doctor will evaluate if the child's growth appears to be leveling off or departing from the child's established growth curve. Past growth patterns are important in determining if the child has a growth problem; the earlier a problem is detected, the earlier it can be treated (if possible) and the better the chance the child has at reaching his or her full growth potential. The doctor may also perform blood tests to determine if a hormone deficiency or other disease is present. X-rays may also be taken to check how the child's bone size compares to the child's height and chronological age.