power point of lec 2

Classifications of genetic disorders
Human diseases in general can roughly be classified in to:

1-Those that are genetically determined.
2-Those that are almost entirely environmentally determined.
3- Diseases with multifactorial (polygenic inheritance) implies that both genetic and environmental had a role in the expression of diseases such as hypertension and diabetes mellitus.

Classifications of genetic disorders:
1- Classical Genetic Diseases:
A. Single gene (or unifactorial) disorders (Mandelian disorders).
B. Chromosomal (cytogenetic) disorders.
C. Multifactorial disorders.
2- Non - Classical diseases (or the single gene disorders with atypical pattern of inheritance)
A. Diseases caused by mutation in mitochondrial genes.
B. Triplet repeat mutations.
C. Genomic imprinting.
D. Gonadal mosaism.
Autosomal: the gene responsible for the phenotype is located on one of the 22 pairs of autosomes (non-sex determining chromosomes).

X-linked: the gene that encodes for the trait is located
on the X chromosome.

Dominant: conditions that are manifest in heterozygotes (individuals with just one copy of the mutant allele).

Recessive: conditions are only manifest in individuals who have two copies of the mutant allele (are homozygous