Genetics Chapter 25

When a human disease is caused by a mutation in a single gene, scientists follow the pattern of inheritance by analyzing charts called human

pedigrees

The use of information about a patient's genotype in order to select a medication or therapy that is specifically suited to that patient is called

personalized medicine

Monozygotic twins

share 100% of the same alleles

Dizygotic twins

share an average of 50% of the same alleles

When a defect in a single gene causes a human disease, the mutant gene often follows

simple Mendelian inheritance patterns

Select the human disorders inherited in an x-linked recessive fashion

Hemophilia A; Androgen insensitivity syndrome; Duchenne muscular dystrophy

Which of the following characteristics of inheritance for hemophilia can be observed in the accompanying pedigree for the family of Queen Victoria and Prince Albert?

Mothers of affected males most often have brothers with the disease; males are more likely to be affected than females

Which observations are consistent with a disease having a genetic basis?

Tay-Sachs disease can occur in 1/2500 births in a specific Eastern European population while the frequency is 1/250,000 across Europe; a cancerous growth of immature nerve cells called neuroblastoma is associated with a deletion in a specific region of chromosome 11; the sleep disorder called narcolepsy has been related to an allele for a faulty neural receptor in dogs. Some humans also suffer from narcolepsy

True or false: a genetic disease is spread to individuals sharing similar environmental situations

false

A dominant genetic disorder can be caused by a ________ mutation, where the product of an altered gene gains a new or abnormal function.

gain-of-function

In one study, autism showed 60% concordance for monozygotic twins and 0% concordance for dizygotic twins. This demonstrates that autism is a

genetic disease

Nontraumatic epilepsy shows a concordance of 70% for monozygotic twins and 6% for dizygotic twins. This demonstrates that nontraumatic epilepsy is a

genetic disease

Select observations that are consistent with a disease having a genetic basis

identical twins share the disease more often than non-identical twins; a human disorder may resemble a disorder known to have a genetic basis in animals; there is a correlation between a human disease and a mutant gene or chromosomal alteration; the disease doesn't spread to individuals sharing similar environmental situations; a person with a disease is more likely to have genetic relatives with the disease than are people in the general population; the disease has a characteristic age of onset; different populations tend to have different disease frequencies

True or false: identical twins share a genetic disease more often than fraternal twins

true

The autosomal recessive human disorder albinism (type I) is caused by a mutation in the gene for

tyrosinase

The disease hemophilia is caused by a deficiency in any one of three blood clotting factors. Two of these factors are encoded by genes on the X chromosome and the other clotting factor gene is located on an autosome. Since mutations in more than one gene can cause hemophilia, this represents

locus heterogeneity

Which statement is true of x-linked dominant disorder such a Rett Syndrome and Aicardi Syndrome?

males die at an early stage of devvelopment

What is the inheritance pattern when a trait occurs with the same frequency in both sexes and two affected heterozygous individuals have, on average, 25% unaffected children?

autosomal dominant

What is the inheritance pattern when a trait occurs with the same frequency in both sexes and an affected offspring can have two unaffected parents?

Autosomal recessive

Rett syndrome, which is inherited in an x-linked dominant manner, is caused by a mutation in the gene for

methyl-CpG-binding protein-2

Select the human disorders inherited in an autosomal dominant fashion

Huntington Disease; Marfan syndrome; Aniridia

What is the inheritance pattern for a trait that more commonly affects males than females and will occur in about 50% of the sons born to the unaffected daughter of an affected male?

x-linked recessive