Pedigree Tracking Genetic Traits: How it s done!
REVIEW Many traits in humans are controlled by genes. Some of these traits are common features like eye color, straight or curly hair, baldness, attached vs. free ear lobes, the ability to taste certain substances, and even whether you have dry or sticky earwax!
REVIEW Other genes may actually cause disease. Sickle cell anemia, muscular dystrophy, cystic fibrosis are each caused by a specific allele of a human gene, and can therefore be inherited from one generation to the next.
Pedigree Human geneticists illustrate the inheritance of a gene within a family by using a pedigree chart. On such a chart, males are symbolized by a square ( ) and females are symbolized by a circle ( ). People who are affected by a disease are symbolized by a dark circle or square.
Pedigrees Allows tracking of inherited genes by understanding who is a carrier, who does not have the gene and who has the gene. If a symbol is colored in: HAS THE GENE If a symbol is not colored in: DOES NOT HAVE THE GENE If a symbol is ½ colored in: CARRIER
CARRIERS However, depending if the gene is dominant or recessive, carriers may or may not have the disease. Sometimes carriers are not represented by a halfcolored in circle, but need to be figured by working with the information. A carrier can only be a female for an X linked recessive trait. Males or Females can be a carrier for an Autosomal linked trait.
What type of inheritance When reading a pedigree, you can determine what type of inheritance the pedigree is. Pedigrees can have the following types of inheritance: Autosomal (non- sex linked) Dominant Autosomal (non-sex linked) Recessive X Sex Linked Dominant X Sex Linked Recessive Y Sex Linked
Autosomal Dominant Both carriers and homozygous dominant have the condition, 11 in this example
Autosomal Dominant Disease Tuberous Sclerosis: Tuberous sclerosis or tuberous sclerosis complex (TSC) is a rare, multi-system genetic disease that causes benign tumours to grow in the brain and on other vital organs such as the kidneys, heart, eyes, lungs, and skin. A combination of symptoms may include seizures, developmental delay, behavioral problems, skin abnormalities, lung and kidney disease.
Autosomal Recessive Only homozygous recessive have the condition, 8 in this example.
Autosomal Recessive Disease Friedreich's ataxia is an inherited disease that causes progressive damage to the nervous system resulting in symptoms ranging from gait disturbance and speech problems to heart disease. Generally, ataxia is a symptom of coordination problems such as clumsy or awkward movements and unsteadiness and occurs in many different diseases and conditions. The spinal cord becomes thinner and nerve cells lose some of their myelin sheath (the insulating covering on some nerve cells that helps conduct nerve impulses).
X Linked Recessive Only a homozygous recessive will show the condition. Must have 2 recessive alleles in females and 1 in males.
X linked Recessive Disease Hunter syndrome is a genetic disorder that primarily affects males. It interferes with the body's ability to break down and recycle specific mucopolysaccharides (types of sugars). A build up of these waste sugars accumulates in the body cells, not allowing them to function. A variety of symptoms are seen with Hunter syndrome included hearing loss, thick heart valves and enlargement of the liver or spleen.
X linked Dominant Must have 1 dominant gene to express the condition. Females only need 1 dominant gene, as do males. If mother is normal and man has the disorder, sons cannot get the disease, only daughters.
X Linked Dominant Disease Aicardi Syndrome is a disease linked to the brain. The corpus callosum (the connector between the left and the right brain) is absent. Seizures are a common side effect. By 3 months, symptoms are apparent and over time condition will impede thought processing and coordination.