1. Class Notes #8: Genetic Disorders

2. I. Inheritance
Genetic disorders can be due to any of the following factors:
A. Monogenetic Disorders: Caused by a mutation in a single gene
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

3. 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

4. B. Chromosomal abnormalities:
Occur when there are not 2 of each chromosome. 1. Trisomy: When there is an extra copy of a chromosome. 2. Deletions 3. Translocations

5. C. Multifactoral Inheritance Disorders: caused by a combination of inherited genes and environmental factors.
Ex: heart disease, diabetes, and most cancers.

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

7. III. Pedigrees
A pedigree is a chart that traces phenotype and genotype in a family to determine whether people carry recessive alleles.
Boxes :males Circles: Females

8. IV. Testing
Gene tests: test for a specific mutation in a DNA sequence.
Chromosomal tests: include karyotypes, which look for extra or missing copies of a chromosome.
Prenatal
Testing: detects
disorders before
birth

9. Summary
Why can lethal alleles pass from generation to generation? What methods can be used to detect and predict genetic disorders?