*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 InheritanceAutosomal 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