You already know… - A chromosome is a structure that carries genetic information Each cell normally has 23 pairs of chromosomes: 1 pair of sex chromosomes 22 pairs of autosomes Both chromosomes in every pair of autosomes consist of the same genes in the same order (homologous chromosomes)  Every person has 2 alleles for each gene

Autosomal Inheritance Autosomal RECESSIVE Inheritance

Autosomal RECESSIVE Inheritance A recessive genetic trait located on an autosome Males and females are equally affected   Heterozygote NO symptoms Carrier Homozygote recessive - Shows symptoms of trait Examples: Cystic fibrosis, albinism, sickle cell disease

Cystic Fibrosis Most common fatal genetic disease affecting Caucasian children and young adults Due to a mutation of a gene on chromosome 7 that encodes a regulator protein Results in a production of abnormal mucus that causes blockages within the lungs and airways Mucus also builds up in the digestive tract making it difficult to digest and absorb nutrients No cure, however treatments are improving

Albinism Due to a mutation on chromosome 9, 11, or 15 People with albinism have little or no pigment in their eyes, skin, or hair Unable to produce or distribute melanin Vision and skin problems Does not usually affect lifespan Diagnosis: eye examinations

Sickle Cell Disease Due to a mutation on chromosome 11 that encodes a subunit of the hemoglobin protein Distorts red blood cells (RBCs) into a sickle shape Sickle shaped RBCs get stuck in blood vessels and are unable to transport oxygen effectively Damages organs and decreases immune function No cure, reduces lifespan by 30 years Most common among African- Americans

Autosomal DOMINANT Inheritance

Autosomal DOMINANT Inheritance A dominant genetic traits located on an autosome Males and females are equally affected   Homozygote dominant or heterozygote - Shows symptoms of the trait Homozygote recessive - Normal Example: Achondroplasia and Huntington’s disease

Achondroplasia Due to mutation of a gene on chromosome 4 More commonly due to sporadic mutation Most common type of short-limbed dwarfism Health problems: shortness of breath, obesity, problems with the spine, buildup of brain fluid

Huntington’s disease Due to mutation of a gene on chromosome 4 Neurodegenerative disorder that leads to dementia Functional abilities gradually worsen overtime Medications help manage the symptoms, but treatments can not prevent the physical, mental and behavioural aspects Time from the onset of the disease to death is about 10-30 years Common causes of death: infections, falls, inability to swallow food