Chapter 24: Medical Genetics

Which of the following characteristics of inheritance can be observed in the accompanying pedigree of a family affected by Tay-Sachs disease?

Affected individuals are offspring of heterozygous parents. The trait occurs in both males and females. An affected offspring can have two unaffected parents.

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 An affected offspring will have at least one affected parent in autosomal dominant inheritance.

Tay-Sachs disease is inherited with an autosomal recessive allele that leads to a defect in the enzyme hexosaminidase A. When cells are collected from patients, cells with different genotypes exhibit different amounts of enzymatic activity. Rank the amount of enzymatic activity that would be detected in a biochemical assay on cells from patients of these genotypes, with the genotype producing the LEAST amount of enzymatic activity on top. Homozygous recessive Heterozygous Homozygous Dominant

Homozygous recessive Heterozygous Homozygous Dominant

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

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

Which statement is true of X-linked dominant disorders such as Rett syndrome and Aicardi syndrome?

Males die at an early stage of development

What tool do scientists use to follow a human pattern of inheritance from generation to generation?

Pedigree analysis

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

Personalized Medicine

Approximately how many human diseases have a genetic basis?

Thousands

Simple Mendelian inheritance is a pattern observed when a human disorder is caused by ______.

mutation in a single gene

Chorionic villus sampling is a procedure for ______.

obtaining a sample of the fetal part of the placenta

Embryos produced by in vitro fertilization can undergo genetic testing by ______.

preimplantation genetic diagnosis

A disease-causing agent made only of protein is called a ______.

prion

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

simple Mendelian inheritance patterns

To study the distribution of disease-causing genes, genetic ______ refers to determining if an individual carries the faulty gene, while genetic ______ relates to assessing the presence of the gene throughout a population.

testing; screening

Select human disorders inherited in an autosomal dominant fashion. Multiple select question. Aniridia Marfan syndrome Phenylketonuria Huntington disease

Aniridia Marfan syndrome Huntington disease

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

Autosomal dominant For autosomal recessive pattern, two affected individuals (who would not be heterozygotes), would have 0% unaffected offspring.

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

Autosomal recessive

Suppose a disease-causing allele shows autosomal recessive inheritance. How could a carrier of this disease-causing allele be identified?

Carriers often show reduced activity for the enzyme encoded by the allele.

Which type of mutation causes a dominant genetic disorder through the production of an altered protein that works against the action of the normal protein?

Dominant-negative

Which type of catalytic activity occurs in prion-caused diseases? Multiple choice question. The normal form of the prion protein catalyzes a reaction that converts other normal proteins to misfolded ones. The normal form of the prion protein catalyzes the digestion of other properly-folded normal proteins. The abnormal form of the prion protein catalyzes a reaction that converts normal proteins to misfolded ones. The abnormal form of the prion protein catalyzes the digestion of the properly-folded normal proteins.

The abnormal form of the prion protein catalyzes a reaction that converts normal proteins to misfolded ones.

Which of the following characteristics of inheritance can be observed in the accompanying pedigree of a family affected by Tay-Sachs disease?

The trait occurs in both males and females. Affected individuals are offspring of heterozygous parents. An affected offspring can have two unaffected parents.

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

True

A method for obtaining fetal cells in a sample of the fluid surrounding the fetus is called ______.

amniocentesis

Marfan syndrome, which is inherited in an autosomal dominant manner, is caused by a mutation in the gene for ______.

fibrillin-1

In the accompanying pedigree, a filled symbol indicates an individual with Huntington disease while a clear symbol shows an unaffected individual. Which of the following characteristics of inheritance can be observed for this affected family?

An affected individual has at least one affected parent. The trait occurs in both males and females.

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

False

True or false: Dizygotic twins share a genetic disease more frequently than monozygotic twins.

False Dizygotic twins share an average of 50% of the same genes while monozygotic twins share 100% of the same genes.

True or false: A disease with a genetic origin in a mouse is unlikely to be an inherited disease in humans.

False Due to evolutionary relatedness, humans share many genetic similarities with animals.

Which observations are consistent with a disease having a genetic basis? Multiple select question. The sleep disorder called narcolepsy has been related to an allele for a faulty neural receptor in dogs. Some humans also suffer from narcolepsy. Tay-Sachs disease can occur in 1/2500 births in a specific eastern European population while the frequency is 1/250,000 across Europe. Smokers are at high risk for developing lung cancer. A cancerous growth of immature nerve cells called neuroblastoma is associated with a deletion in a specific region of chromosome 11. People from several different families living in a region with high levels of air pollution develop lower respiratory tract infections.

The sleep disorder called narcolepsy has been related to an allele for a faulty neural receptor in dogs. Some humans also suffer from narcolepsy. 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.

What is the inheritance pattern for a trait that more commonly affects males than females and can often be observed in brothers or fathers of a woman who has affected sons?

X-linked recessive

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

X-linked recessive Since the daughter is unaffected, the trait must be inherited as an X-linked recessive.

Consider the accompanying partial pedigree showing inheritance of hemophilia in the family of Queen Victoria and Prince Albert. If Xh is the allele for hemophilia and XH is the allele for normal blood clotting, which genotypes are missing among the children of Alice of Hesse and her husband, in the middle of the figure?

XHXH XHY

Twins that are genetically identical to each other are called ______ twins.

monozygotic

Select the human disorders that are inherited in an autosomal recessive fashion. Multiple select question. Huntington disease Sickle cell disease Phenylketonuria Cystic fibrosis

Sickle cell disease Phenylketonuria Cystic fibrosis

Select the human disorders that are inherited in an autosomal recessive fashion. Multiple select question. Sickle cell disease Phenylketonuria Cystic fibrosis Huntington disease

Sickle cell disease Phenylketonuria Cystic fibrosis

Which of these is a common example of widespread genetic screening of newborns to identify certain disorders?

Test for excess phenylalanine indicating phenylketonuria (PKU)

True or false: Genetic diseases often show a specific age of onset.

True The time at which a genetic disease arises can be correlated with the actions of genes at specific stages of development.

Genetic testing is used to determine whether a(n) ______ has a disease-causing gene, while genetic screening is used to determine how frequently the gene is found in a(n) ______.

individual; population

Amniocentesis is a procedure for ______.

obtaining fetal cells in a sample from the fluid surrounding the fetus

A prion is a disease-causing agent made ______.

only protein

Monozygotic twins ______.

share 100% of the same alleles

When a human disease is caused by a mutation in a single gene, the pattern of inheritance is called ________ Mendelian inheritance.

simple

The abnormal form of a prion protein causes a neurodegenerative disease by ______.

catalyzing the conversion of the normal protein form to the abnormal form

Preimplantation genetic diagnosis is a method testing for genetic diseases in ______.

embryos produced by in vitro fertilization

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

A dominant genetic disorder can be caused by ______, a situation where one functional copy of an allele is not sufficient to produce a normal phenotype.

haploinsufficiency

In the accompanying pedigree, a filled symbol indicates an individual with Huntington disease while a clear symbol shows an unaffected individual. Considering the symbol for individual II-5, you conclude that her father, I-1 is ______ allele for Huntington disease.

heterozygous for the autosomal dominant

A situation where a disease may be caused by mutations in two or more different genes is called ______.

locus heterogeneity

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

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

What is the inheritance pattern for a trait that occurs with equal frequency in both sexes and will be inherited, on average, by 50% of the offspring of an affected individual who had only one affected parent?

Autosomal dominant

What is the inheritance pattern for a trait that is more likely to occur in females when it is lethal to males?

X-linked dominant

Consider the children of II-6 and II-7 in the accompanying pedigree for a family affected by Tay-Sachs disease. What is one genotype that could have been produced by these two parents but was not observed?

Unaffected homozygote

Consider the children of II-6 and II-7 in the accompanying pedigree for a family affected by Tay-Sachs disease. What is one genotype that could have been produced by these two parents but was not observed? White mom half dad half two daughters

Unaffected homozygote

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

tyrosinase

Select all that apply Select observations that are consistent with a disease having a genetic basis A disease where a child is affected but not the child's parents cannot be a genetic disease. A person with a disease is more likely to have genetic relatives with the disease than are people in the general population. A human disorder may resemble a disorder known to have a genetic basis in animals. Different populations tend to have different disease frequencies. There is a correlation between a human disease and a mutant gene or chromosomal alteration. The disease has a characteristic age of onset. Identical twins share the disease more often than non-identical twins. 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. A human disorder may resemble a disorder known to have a genetic basis in animals. Different populations tend to have different disease frequencies. There is a correlation between a human disease and a mutant gene or chromosomal alteration. The disease has a characteristic age of onset. Identical twins share the disease more often than non-identical twins. The disease doesn't spread to individuals sharing similar environmental situations.

Select observations that are consistent with a disease having a genetic basis. Multiple select question. A person with a disease is more likely to have genetic relatives with the disease than are people in the general population. A disease where a child is affected but not the child's parents cannot be a genetic disease. Identical twins share the disease more often than non-identical twins. The disease has a characteristic age of onset. 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. Different populations tend to have different disease frequencies. A human disorder may resemble a disorder known to have a genetic basis in animals.

A person with a disease is more likely to have genetic relatives with the disease than are people in the general population. Identical twins share the disease more often than non-identical twins. The disease has a characteristic age of onset. 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. Different populations tend to have different disease frequencies. A human disorder may resemble a disorder known to have a genetic basis in animals.

Which observations are consistent with a disease having a genetic basis? Multiple select question. People from several different families living in a region with high levels of air pollution develop chronic obstructive pulmonary disease. People who have diets high in saturated fats are likely to develop atherosclerosis. Someone with a diagnosis of retinitis pigmentosa has learned that there are family members in the preceding three generations who had the disease. Nephroblastoma is a cancer of the kidney that typically develops in children and is only rarely found in adults. One family in the neighborhood has one parent and several children with severe hearing loss. No one in any of the other nearby families has deafness.

Someone with a diagnosis of retinitis pigmentosa has learned that there are family members in the preceding three generations who had the disease. Nephroblastoma is a cancer of the kidney that typically develops in children and is only rarely found in adults. One family in the neighborhood has one parent and several children with severe hearing loss. No one in any of the other nearby families has deafness.

Personalized medicine can be used to select a ______.

medication preventative measure therapy

Which observations are consistent with a disease having a genetic basis? Multiple select question. Smokers are at high risk for developing lung cancer. People from several different families living in a region with high levels of air pollution develop lower respiratory tract infections. The sleep disorder called narcolepsy has been related to an allele for a faulty neural receptor in dogs. Some humans also suffer from narcolepsy. 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. 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.

A small portion of the fetal part of the placenta is removed to prepare a karyotype in the process called ______.

chorionic villus sampling