27:3 Genetic Disorders

• Objectives:

• Describe genetic disorders in humans

• Give examples of how genetic counseling can help families

Errors in Chromosome Number

• Some people can be born with more or fewer than 23 chromosomes

• This is caused by the chromosomes not pulling apart during mitosis phase of meiosis

• It can happen to any chromosome but when it happens on the sex chromosomes certain traits show up.

• If a male is conceived and has only a Y chromosomes, that child will die before it is born

• If a XXY male or an XO female is conceived they will live but are unable to make new sex chromosomes

• If a child is born with an extra chromosome then the child is said to have Downs Syndrome, which means they will learn at a slower rate, have heart problems and have different physical traits.

Genetic Disorders and Autosomes

• Some genetic disorders can be found on autosomes. These are the genes that are not sex genes

• These result if a chromosome does not pull apart during meiosos

• Dyslexia, which is a reading and writing disability, is caused by a dominant gene

• PKU is a genetic disorder where the body does not break down some chemicals properly

• This can cause brain damage• Today all babies are tested for PKU at birth

and if it is found then a special diet is started with very few of these chemicals and the baby can develop normally

• Hemophilia, Cystic Fibrosis are other genetic disorders

Genetic Counseling

• Genetic counseling is the use of genetics to predict and explain the traits in children

• A genetic counselor can tell if a problem is cause by genes

• The counselor looks at the parents pedigree and determine if they are at risk of having a child with a genetic disorder

• A pedigree is a diagram which shows how a certain trait is passed along in a family