Chromosomal Mutations and Karyotypes

Genetic Variation- differences in genetic material Caused by: segregation crossing over (during meiosis) recombination (during fertilization) Most genetic Variation is normal.

Mutations are sudden changes in the structure or the amount of genetic material. Mutants are the first individuals showing the new trait. In order for a mutation to be inherited in a sexually reproducing organism, it must be present in the DNA of a gamete (sex cell).

In mutations, the DNA sequence is altered, therefore a different, or no protein will be made. Effect 1. A different protein is made 2. or no protein is made 3. the function that protein would have done is not accomplished This could be harmful to the organism.

Mutations cause a Change in a Protein 1. the DNA sequence is altered 2. amino acid sequence is different 2. therefore a different, or no protein will be made. Impact The different protein that is made by an altered gene may not be able to perform the intended function. This could be harmful to the organism.

What could cause these alterations? Chemical exposure (alcohol, other drugs, smoking, etc.) UV light X-Rays

Examples

Karyotypes A karyotype is a picture of all of the chromosomes and their characteristics. The picture is taken from dividing cells so that all chromosomes will have a homologous copy. Chromosomes are matched up with their homologue based on size and banding pattern.

Normal Female Before Arranging the Chromosomes

Normal Female Normal Male

Female with Down’s Syndrome

Male with too Many X Chromosomes

Sickle Cell Disease is a group of inherited red blood cell disorders. Normal red blood cells are round like doughnuts, and they move through small blood tubes in the body to deliver oxygen. Sickle red blood cells become hard, sticky and shaped like sickles used to cut wheat. When these hard and pointed red cells go through the small blood tube, they clog the flow and break apart. This can cause pain, damage and a low blood count, or anemia. PHENYLKETONURIA (PKU) is an inherited error of metabolism caused by a deficiency in the enzyme phenylalanine hydroxylase. Loss of this enzyme results in mental retardation, organ damage, unusual posture and can, in cases of maternal PKU, severely compromise pregnancy Tay-Sachs disease is a fatal inherited disease of the central nervous system. The most common form of the disease affects babies. Affected babies appear healthy at birth and seem to develop normally for the first few months of life. After this time, development slows and symptoms begin. Cystic fibrosis (CF) is an inherited disease of your mucus and sweat glands. It affects mostly your lungs, pancreas, liver, intestines, sinuses, and sex organs. Normally, mucus is watery. It keeps the linings of certain organs moist and prevents them from drying out or getting infected. But in CF, an abnormal gene causes mucus to become thick and sticky. The mucus builds up in your lungs and blocks the airways. This makes it easy for bacteria to grow and leads to repeated serious lung infections. Over time, these infections can cause serious damage to your lungs. The thick, sticky mucus can also block tubes, or ducts, in your pancreas. As a result, digestive enzymes that are produced by your pancreas cannot reach your small intestine. These enzymes help break down the food that you eat. Without them, your intestines cannot absorb fats and proteins fully. Huntington’s disease (HD) is a fatal hereditary disease that destroys neurons in areas of the brain involved in the emotions, intellect, and movement. The course of Huntington’s is characterized by jerking uncontrollable movement of the limbs, trunk, and face (chorea); progressive loss of mental abilities; and the development of psychiatric problems.