February 10, 2015 Warm-up: Normal human red blood cells are a round, closed donut shape and are responsible for transporting oxygen throughout the body. What would be the danger of having red blood cells shaped like a crescent moon?

Genetic disorders DISEASES PASSED DOWN THROUGH GENES

Link to Mutations  Gene mutations can be either inherited from a parent or acquired. A hereditary mutation is a mistake that is present in the DNA of virtually all body cells. Moreover, the mutation is copied every time body cells divide

 Mutations occur all the time in every cell in the body. Each cell, however, has the remarkable ability to recognize mistakes and fix them before it passes them along to its descendants.  But a cell's DNA repair mechanisms can fail, or be overwhelmed, or become less efficient with age. Over time, mistakes can accumulate.

Sickle Cell Anemia  An inherited, chronic disease in which the red blood cells, normally disc-shaped, become crescent shaped.  As a result, they function abnormally and cause small blood clots. These clots give rise to recurrent painful episodes called "sickle cell pain crisis".

Sickle cell anemia  Sickle cell is caused by a mutation that affects hemoglobin  Hemoglobin is a protein in red blood cells that carries oxygen  Sickle-shaped red blood cells cannot carry as much oxygen as normal cells and also clog blood vessels.

Inheritance of sickle cell anemia  A person with one normal allele and one sickle-cell allele will produce both normal hemoglobin and abnormal hemoglobin.  HOWEVER! They will have enough normal hemoglobin to carry oxygen throughout the body.  A person with two sickle-cell alleles will have the disease.

Cystic fibrosis X-rays of mucus in the lungs

Cystic fibrosis  Genetic disorder in which the body produces abnormally thick mucus in the lungs and intestines.  The thick mucus fills the lungs, making it hard to breathe.  Two mutated alleles, one from each parent.

Down’s Syndrome The individual has an extra copy of chromosome 21. Instead of a pair of chromosomes, a person with Down’s syndrome has three copies. Most often occurs when chromosomes fail to separate properly.

Down’s Syndrome or Trisomy 21

Symptoms of Down Syndrome  Upward slant to eyes.  Small ears that fold over at the top.  Small, flattened nose.  Small mouth, making tongue appear large.  Short neck.  Intellectual disabilities  Low muscle tone  Loose joints

Hemophilia  Hemophilia is the oldest known hereditary bleeding disorder.  A person’s blood clots very slowly or not at all.  So severe that a single cut on the finger can have dangerous effects  Hemophilia is caused by a recessive allele on the X chromosome  Sex-linked disorder, occurs more frequently in males than females.

Treatment of Genetic Disorders  Pedigrees: a chart or “family tree” that tracks which members of a family have a particular trait.  Karyotypes: picture of all the chromosomes in a person’s cell.  Genetic Counseling  Dealing with Genetic Disorders: most genetic disorders do not prevent people from living active, productive lives.