Class Notes #7: Genetic Disorders

Genetic disorders can be due to any of the following factors:

A. Monogenetic Disorders: Caused by a mutation in a single gene

1. Autosomal recessive alleles:a. You may be a carrier and not know it, since the dominant allele masks the recessive.b. Lethal alleles are passed in these heterozygous carriers.

Ex: Cystic fibrosis

I. Inheritance

2. Autosomal dominant alleles: Person would only need one copy of the dominant allele to have the disease.ex: Huntington’s disease

3. Sex linked genes: males only need one recessive allele to have a disorder found on a sex chromosome. Ex: hemophilia

Occur when there are not 2 of each chromosome.1. Trisomy: When there is an extra copy of a chromosome.2. Deletions3. Translocations

B. Chromosomal abnormalities:

C. Multifactoral Inheritance Disorders: caused by a combination of inherited genes and environmental factors.

Ex: heart disease, diabetes, and most cancers.

A. Genetic counselors are health care professionals who determine your risk of developing a disorder, or your risk of having children with a disorder.

II. Genetic Counselors

A. A pedigree is a chart that traces phenotype and genotype in a family to determine whether people carry recessive alleles.

B. Boxes :males Circles: Females

III. Pedigrees

A. Gene tests: test for a specific mutation in a DNA sequence.

B. Chromosomal tests: include karyotypes, which look for extra or missing copies of a chromosome.

C. PrenatalTesting: detects disorders beforebirth

IV. Testing

Why can lethal alleles pass from generation to generation?

What methods can be used to detect and predict genetic disorders?

Summary