Chapter 11: Mendel and the gene idea 1

dominantly inherited gene idea

what are the 2 dominantly inherited disorders?

1. huntington’s disease (also referred to as chorea)

2. achondroplasia

what is Huntington’s disease?

• huntigntons disease (HD) is a degenerative diseases of the nervous system

• the diseases has no obvious phenotypic effects until the individual is about 35 to 40 years of age

• if one parent is a carrier (Hh), there is a 50% chance that their children will inherit the disease

• only individuals with homozygous recessive will not inherit this disease

• there is no cure as its inherited genetically

• mutation leads to gradual damage of brain tissue (affects the muscle coordination and leads to cognitive decline and dementia)

• the earliest symptoms are a general lack of coordination. As the disease advances, uncoordinated, jerky body movements become more apparent (chorea), along with a decline in mental abilities

what is achondroplasia?

• a form of dwarfism caused by a rare dominate allele

what is the frequency of dominant alleles?

• dominant alleles are not necessarily more common in populations than recessive alleles

what is polydactyly?

• when a person is born with more than 5 fingers or (and) toes