Ms. Smith's Biology: Period 3

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How is it inherited?
What type of mutation occurs?
Characteristics of disease
Duchenne Muscular Dystrophy
DMD is a disease passed down hereditarily. It is passed from a mutated X chromosome, which is why it is only inherited by boys. Girls require two X chromosomes which means if only one is defected they will not be affected by the disease, just carry it. Males on the other hand are affected because they only have one X chromosome. The dystrophy can only be inherited from the mother because the father can't pass down X chromosomes. There is a 50% probability mothers will give the disease to their sons.
DMD is caused by a defected gene in male chromosomes, (the X chromosome). The people affected by this disease have a mutated DMD gene, which is found on the short arm of the X chromosome. This chromosome fails to make dystrophin. Since the mutation occurs on the X chromosome that’s why men have a higher chance of getting the disease (they only have one X chromosome).
Muscular dystrophy is muscle weakness that progresses over time. Early signs include frequent falling, difficulty getting up from a seated position, calf muscles become large, and the inability to life knees. Most children with this disorder have weak motor skills like trouble running and jumping. The leg and pelvis muscles start to weaken first and by age 11 the child loses the ability to walk. Death usually occurs before the child reaches the age of 20. The main cause of death is respiratory failure or pulmonary infections.
There is no cure for Duchenne Muscular Dystrophy, however doctors recommend that patients exercise daily, join support groups to help cope with the disorder, and begin physical therapy to help increase mobility of the joints. In the future, doctors are predicting that therapy for genes may be used for patients with DMD, but for now there are no ways to prevent this disease.
Klinefelter's Syndrome
Klinefelter’s Syndrome is not inherited. It normally happens randomly during the formation of reproductive cells. Nondisjunction, the failure of chromosome pairs to separate properly during cell division, occurs which results in a reproductive cell with an abnormal number of chromosomes. This is how a cell can gain one or more extra copies of the X chromosome.
Nondisjunction is the mutation that occurs. This is when chromosome pairs fail to separate during meiosis.
Men with Klinefelter’s Syndrome usually have increased testosterone concentrations, fusion of the forearm bones and other bone abnormalities, and underdevelopment of the penis, scrotum, and testes. They also have trouble producing sperm. Men with this disease normally have gynecomastia, enlarged breasts. Also, Klinefelter’s result in long legs and arms, learning disabilities, mental retardation, and violent behavior. They also have an increased risk of cancer, lung disease, osteoporosis, ADHD, and depression.
There is no cure for Klinefelter’s Syndrome, but patients with this disease usually live normal and productive lives.
Turner's Syndrome
Turner's Syndrome cannot be inherited. This happens spontaneously during cell reproduction in which a cell is not properly divided.
For normal females, the sex chromosomes are XX, but for females with Turner’s Syndrome, they may not have another X chromosome or they may be missing part of one of their X chromosome.
People with Turner’s are often very short, in fact, the average height of a woman with Turner’s is 4’8”. People with this disorder may also experience lymphedema: puffiness or swelling of the hands and feet, and early on in their life, they may lose all ovarian function. For people that have Turner’s Syndrome, loss of ovarian function is almost inevitable, and they lose the essential hormone estrogen, and unless the affected girls do not have estrogen treatment, they will not go through puberty. Some of the other characteristics of Turner’s are kidney problems, skeletal problems, short fingers, a webbed neck, a small jaw, low hairline in the neck, and very large ears.
Sadly, there is no cure for Turner’s syndrome, women may take growth hormones to help increase height and spur sexual maturation. A child may also go through Growth Hormone Therapy (GH) to have a greater chance of reaching average height at adulthood. Another treatment is Estrogen Replacement Therapy. This type of therapy is treated throughout the woman's life where it stimulatesthe growth of breasts, pubic hair, and sexual maturation.
Cystic Fibrosis
  • Cystic Fibrosis is an inherited, recessive disorder.
  • The disorder is not apparent in a person unless both of their parents’ homologous chromosomes carry the trait.
  • The parents each carry one copy of the mutated gene, but often times do not show signs or symptoms of the disease.
  • A person who has two abnormal copies of the cystic fibrosis transmembrane conductance regulator (CFTR) gene are at high risk for cystic fibrosis.
  • The CFTR gene is in chromosome 7.
  • The CFTR gene is a large gene that contains 180,000 base pairs and 1,480 amino acids
  • There are more than 1,500 mutations associated with the disease that have been detected.
  • These mutations are classified according to the affect they have on the function of the CFTR protein
  • Class I mutations result in no CFTR proteins being made.
  • Class II mutations inhibit the CFTR protein from getting to its location on the cell membrane.
  • Class III mutations cause problems with the function of the CFTR protein.
  • Class IV mutations lessen the ability of the channel to transport chloride across the membrane.
  • Class V mutations lessen the amount of functions to to produce the CFTR protein.
The main effect on people who have cystic fibrosis is the body’s excessive production of mucus. Cystic fibrosis can also lead to problems with the digestive system because the mucus interferes with the function of the pancreas.Children that suffer from Cystic Fibrosis can have problems such as poor weight gain, loose stools, and respiratory infections. In adolescents with cystic fibrosis, they can have pancreatitis, diabetes, nasal polyps, and liver cirrhosis.
There is no cure for Cystic Fibrosis, however, there are treatments that make living with CF easier. A few examples are:
  • Using the chest-clapper which imitates hands clapping over the ribs to loosen the mucus.
  • Using an inflatable-vest which vibrates with a frequency that also loosens the mucus in the chest.
  • Using a feeding tube to help give the body nutrients since Cystic Fibrosis interferes with the digestive system and makes it hard to absorb nutrients from food.
  • Having a lung-transplant which is used during a very bad lung infection occurring in Cystic Fibrosis.
  • Having Bowel surgery which is used when there is blockage in the bowel.
Sickle Cell Anemia
Sickle Cell Anemia is inherited as a recessive autosome which is a non sex chromosome. It is caused from a mutation in the gene for hemoglobin. The disease lasts your whole life and is inherited from your parents. Both genders can inherit sickle cell anemia. People with this disease inherit a gene for sickle hemoglobin from each parent so they have two sickle cell genes. If someone inherits only one sickle cell gene, one parent has sickle cell gene and the other has a normal gene, the child will be a sickle cell carrier, someone with only one sickle cell gene. People only carrying one sickle cell gene make sickle hemoglobin and normal hemoglobin. A sickle cell carrier has rare problems but still can pass it down to their offspring.
Sickle cell anemia is caused by a change of a letter in the DNA that alters one of the amino acids in the hemoglobin protein. This change causes valine to be postioined where glutamic acid should be causing the homoglobin molecules to stick together. This forms long fibers that distort the shape of red blood cells into a cresent, or sickle, shape.
Red blood cells are destroyed due to this hereditary disease, and are made into a stiff “sickle” shape.
Some characteristics are eye problems like jaundice, severe episodes of pain in the bones or muscles, or abdomen, as well as delayed growth.
Also pale skin, exhaustion and difficulty breathing are known symptoms of chronic anemia that relate to Sickle Cell Anemia.
This disease commonly occurs in individuals with African descent, the Middle East, Mediterranean, and India.
-ongoing blood transfusions
-hydroxyurea drug use
-bone marrow transplant
-oxygen treatment
-stem cell transplants
Werner Syndrome
Werner's Syndrome is inherited when both the mom and dad of the child affected, have a mutated WRN gene. Though the parents' do not show the mutation, they carry it. This is called a recessive inheritence pattern.
Over 60 mutations to the WRN gene must occur in order for Werner's Syndrome to occur. The WRN gene is respnsible for directing the proteins that are involved in DNA replication, repair and structure. When the WRN gene is damaged, the Werner proteins it produces are reduced, interupting DNA transcription, replication and restoration.
- hoarse voice
- thin, hardened skin
-gray/ loss of hair
-"bird- like" facial appearance
- skinny limbs
-large torso
-skin ulcers
-type 2 diabetes
-deminished fertility
-severe hardening of arteries
- Therapy for aggressive skin ulcers
- Controlling Type II diabetes
- Screening for cancer and other associated diseases
- Avoid smoking
- Exercise to avoid unnecessary weight gain
Huntington's Disease
Huntington’s disease is passed down from generation to generation when he/ she inherits’ a larger huntingtin gene from ONE parent. As the number of genes passed down becomes larger and larger, the signs of having Huntington’s show at an earlier and earlier age.
A mutation in the HTT gene causes this disorder. A protein called huntingtin is made from the instructions provided by the HTT gene. The function of this protein in unknown but it seems to be an important part of the nerve cells in the brain. The HTT mutation involves a DNA segment known as CAG (cytosine, adenine, and guanine). The normal CAG segment is repeated 10 to 35 times and for people with HD it is repeated 36 to above 40 times. When the CAG segment is increasing larger than normal it leads to the production of an abnormally long version of the huntingtin protein containing large sections of amino acid & glutamine.
Some characteristics of this disorder include:
Hallucinations, paranoia, psychosis, emotional problems (social), trouble walking, confusion, anxiety, lose ability to control movement, stress, tension, difficulty swallowing, problems speaking, unusual reflexes , and dementia (memory, thinking, speech, behavior, and judgment).
There has not been any medical advancements developed to fully cure this disorder but there are treatments to slow down its process and help control the person's emotions and movements for as long as possible. Depending on the symptoms the person shows the medications vary. Most of the medicines prescribed to patients with HD come with side effects such as fatigue, restlessness, and hyperexcitablility. It is very significant that people with HD stay active and healthy because individuals who excercise tend to do better than those who don't. It is common for people with HD to have thoughts of suicide and feel depressed. If you are someone caring for a person with HD, it is crucial that you observe their symptoms and treat them appropriately.