Chapter 24 Medical Genetics

Place the steps by which a cloned gene is transferred into human cells using a retroviral technique in order, with the first step at the top.

- A gene of interest is placed into a viral vector. - The virus is taken up by cells via endocytosis. - The viral coat disassembles, releasing the viral genome into the cytosol. - The genome is reverse-transcribed into DNA. - The viral DNA is imported into the nucleus. - The gene of interest is integrated into a chromosome of the target cell by recombination.

Place the steps by which a cloned gene is transfered into human cells via liposomes in order, with the first step at the top.

- The DNA containing the gene of interest is complexed with liposomes. - DNA liposome complexes are taken into cells via endocytosis. - DNA is released into the cytosol. - DNA is imported into the nucleus. - DNA is integrated into a chromosome of the target cell by recombination.

Match the life stage on the left to the type of screening on the right that would be used to detect a genetic disease.

-Fetus: Amniocentesis and karyotyping to detect chromosomal abnormalities -Newborn: Test for excess phenylalanine demonstrating phenylketonuria (PKU) -Adult: Test for carrier status if one belongs to a family with a history of a specific disease

Select human disorders inherited in an autosomal dominant fashion.

-Marfan syndrome -Huntington disease -Aniridia

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?

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

Select treatments for patients with adenosine deaminase (ADA) deficiency.

-PEG-ADA treatment -Gene therapy -Bone marrow transplant

Which factors determine the proper dose of a drug to prescribe for a patient?

-Rate of transport of the drug into cells where the it will have its effect -Rate of transport of an orally-administered drug from the digestive tract into the bloodstream -Ability of drug to affect the function of a target protein -Rate of excretion of drug from the body -Ability of drug to be metabolized by the liver

Select all that apply Select observations that are consistent with a disease having a genetic basis.

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

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

The accompanying pedigree shows the inheritance of Huntington disease with filled symbols and also indicates which combination of four possible forms (A, B C, D) of a molecular marker called G8 that the person has inherited. What is the one possible phenotype and marker combination that is missing among the children of the couple surrounded by the circle?

BB with Huntington disease

The accompanying pedigree shows the inheritance of Huntington disease with filled symbols and also indicates which combination of four possible forms (A, B C, D) of a molecular marker called G8 that the person has inherited. Although there are some exceptions, the inheritance of Huntington disease is most closely associated with which form of the G8 marker in this pedigree?

C

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

A technique where genetic manipulations occur outside of the body, and then the products are reintroduced into the body is called a(n) ________ _________ approach.

Ex vivo

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

Pedigree analysis

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

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

chorionic villus sampling

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

false

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

fibrillin-1

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

The linkage of alleles or molecular markers along a single chromosome is called a ______.

haplotype

The odds ratio is the odds of ______ a disease for individuals carrying a specific SNP versus the odds of ______ a disease for individuals not carrying the same SNP.

having; having

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

Molecular profiling is ______.

identification of the genes that play a role in the development of a specific type of cancer

A major disadvantage of using liposomes as vectors to transfer cloned genes is ______.

low gene transfer efficiency

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

mutation in a single gene

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

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

preimplantation genetic diagnosis

The gene delivery system used to treat adenosine deaminase deficiency in the first human gene therapy was ______.

retroviruses

The International HapMap Project is an effort to identify differences in human DNA sequences by identifying ______.

single-nucleotide polymorphisms

In a genome-wide association study, the goal is to identify ______ which show a significantly different frequency between a control group and a group of individuals affected by a specific disease.

single-nucleotide polymorphisms (SNPs)

Pharmacogenetics is the ______.

study of genetic variations that cause differing responses to drugs

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

The major disadvantage to using viral vectors to transfer cloned genes is ______.

the potential for an immune response

Gene ________ is the introduction of cloned genes into somatic cells to treat disease.

therapy

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

Scientists have been working on reducing the inflammatory response evoked by ________ vectors, to improve the safety of gene therapy.

virus

Select the types of diseases that are being investigated as potential targets for gene therapy.

-Lung -Cancer -Blood -Metabolic -Muscular

Which best describes a haplotype?

A haploid genotype showing linkage of alleles or molecular markers along a single chromosome

One form of severe combined immune deficiency disease (SCID) is caused by inheriting two defective copies of the ______ gene that encodes an enzyme involved in purine metabolism crucial to the maintenance of healthy immune system cells.

ADA

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 occurs with the same frequency in both sexes and two affected heterozygous individuals have, on average, 25% unaffected offspring?

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

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

Sickle cell disease, hemophilia, and SCID are all diseases for which gene therapy may be useful. What type of disease are these?

Blood

Which method can identify genes that are active in cancer cells but inactive in normal cells?

DNA microarray analysis

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

False

A single individual who first had a disease-causing allele is called a

Founder

A worldwide effort to identify human genetic variation observed for SNPs and other variants is called the International __________ Project

HapMap

What types of human diseases are the most straightforward targets for gene therapy?

Inherited diseases involving a single gene abnormality

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

Males die at an early stage of development

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

Test for excess phenylalanine indicating phenylketonuria (PKU)

Which type of catalytic activity occurs in prion-caused diseases?

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

Approximately how many human diseases have a genetic basis?

Thousands

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

In which way are viruses used for gene transfer different from their wild-type counterparts?

Viruses used in gene transfer cannot replicate within target cells.

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

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

amniocentesis

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

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

An advantage of using liposomes as vectors to transfer cloned genes is that liposomes ______.

do not elicit an immune response

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

embryos produced by in vitro fertilization

When an experiment or treatment involves genetic manipulation outside of the body, followed by reintroduction into the body, it is called an ______ approach.

ex vivo

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

false

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

The most common nonviral technique to transfer a cloned gene into human cells involves lipid vesicles called _________.

liposomes

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

locus heterogeneity

A prion is a disease-causing agent made ______.

only of protein

The study of genetic variations that cause differing responses to drugs is called ______.

pharmacogenetics

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

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

simple Mendelian inheritance patterns

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.

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

To identify SNPs for which the frequency is significantly different between a control group and a group of individuals affected by a disease, a(n) _________ _________ is determined and its significance can be evaluated based on the calculation of a(n) _________ value.

-odds ratio -P

Personalized medicine can be used to select a ______.

-preventative measure -therapy -medication

A patient with ADA deficiency can be treated with a bone marrow ________, injections of purified _______ enzyme coupled with polyethylene glycol, or gene __________.

-transplant -ADA -therapy

DNA microarrays can be used to ______.

compare gene activity in cancer cells and normal cells

The goal of a ______ study is to find a relationship between one or more single-nucleotide polymorphisms (SNPs) and a disease or other human trait.

genome-wide association

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

The process of identifying the genes that play a role in the development of a specific type of cancer is called ______.

molecular profiling

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

monozygotic

Chorionic villus sampling is a procedure for ______.

obtaining a sample of the fetal part of the placenta

Amniocentesis is a procedure for ______.

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

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

prion

To conduct a genome-wide association study, the ______ of a large group of individuals who are afflicted with the same disease are compared to those of a large group of people without the disease.

single-nucleotide polymorphisms (SNPs)

Genetic variation in the ability to metabolize the anticoagulant drug warfarin is shown by polymorphisms in the CYP2C9 gene, which encodes a liver enzyme called _________ P450.

cytochrome

Select all that apply Select the human disorders that are inherited in an autosomal recessive fashion.

-Phenylketonuria -Cystic fibrosis -Sickle cell disease

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

-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.

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?

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

Place the steps used to treat a patient with adenosine deaminase deficiency via gene therapy in order, with the first step at the top.

- Lymphocytes were removed from the patient and cultured in the lab. - The lymphocytes were transfected with a retrovirus that had been genetically engineered to contain the normal ADA gene. - The retroviral genetic material was inserted into the chromosomal DNA of the lymphocytes. - The lymphocytes were reintroduced back into the patient.

If both copies of the ______ gene are defective, deoxyadenosine accumulates within the individual, which can lead to a severely compromised _________ system.

-ADA -immune

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. -An affected offspring can have two unaffected parents. -The trait occurs in both males and females.

An examination of the genomes of many different individuals to determine if a specific genetic variant is associated with a human disease is called a genome-wide _________ ___________.

association study

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

In determining the proper dose of a drug to give a patient, which factors need to be considered? Whether the patient has a gene that ______.

-encodes a target protein with a different shape that will not effectively bind to the drug -would cause faster metabolism of the drug than in other patients -would slow transport of the drug from the digestive system to the bloodstream

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