Chapter 24 Gen

Question 1

Haploinsufficiency

Answer 1

Heterozygote has 50% of functional protein

Question 2

Gain of function mutation

Answer 2

The mutation changes protein so it gains a new protein

Question 3

Dominant negative mutation

Answer 3

The mutant gene products acts antagonistically to the wild-type gene product

Question 3

How autosomal dominant works

Answer 3

1. An affected offspring usually has one or both affected
   parents
   * Can be altered by reduced penetrance
2. An affected individual with only one affected parent is
   expected to produce (on average) 50% affected offspring
3. Two affected, heterozygous individuals will have (on
   average) 25% unaffected offspring
4. The trait occurs with the same frequency in both sexes
5. For most dominant disease-causing alleles, the
   homozygote is more severely affected with the disorder

Question 3

How autosomal recessive works

Answer 3

1. Frequently, an affected offspring will have two unaffected
   parents
2. When two unaffected heterozygotes have children, the
   percentage of affected children is (on average) 25%
3. Two affected individuals will have 100% affected children
4. The trait occurs with the same frequency in both sexes

Question 3

Huntington’s disease

Answer 3

The major symptom of the disease is the degeneration of
certain types of neurons in the brain
* This leads to personality changes, dementia, and early
death (usually in middle age)
* HD is the result of a mutation in a gene that encodes a
protein named huntingtin
* The mutation adds a polyglutamine tract to the protein
* This causes aggregation of the protein in neurons

Question 3

How is huntingtons disease inherited?

Answer 3

inherited in an autosomal dominant manner