Chapter 24 LS (Genetics)

Identify observations that 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.

How can abnormal forms of the prion protein arise within an individual?

-A person can be infected by eating meat from an animal with the disease. -A person may have inherited an allele that causes their normal prion protein to convert to an abnormal one at a low rate.

Which of the following are human inherited diseases that are caused by prions?

-Creutzfeldt-Jakob disease -Familial fatal insomnia

Select features that are consistent with a disease having a genetic basis.

-Different populations tend to have different disease frequencies. -A person with a disease is more likely to have genetic relatives with the disease than are people in the general population. -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 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.

Which of the following are areas of social and ethical concern regarding genetic testing and screening?

-Distress over learning about carrying the gene for an incurable disease -Potential discrimination in obtaining jobs or medical insurance

Select human diseases that are inherited in an X-linked recessive fashion.

-Hemophilia A -Duchenne muscular dystrophy -Androgen insensitivity syndrome

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

Select human disorders inherited in an autosomal dominant fashion.

-Marfan syndrome -Aniridia -Huntington disease

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

-Phenylketonuria -Cystic fibrosis -Sickle cell disease

Which of the following are infectious diseases caused by prions?

-Scrapie -Kuru -Mad cow disease

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

Personalized medicine can be used to select a

-medication -therapy -preventative measure

Place the steps of preimplantation genetic diagnosis in the correct order with the first step at the top.

1) Remove one or two cells from each embryo at the eight-cell stage 2) Perform genetic testing such as PCR analysis and DNA sequencing to identify genetic abnormalities 3) Transfer embryos that do not carry genetic abnormalities to the mother for implantation

Monozygotic twins _________.

100%

What can cause prion disease in humans when the products of an affected animal are consumed?

Abnormal form of the prion protein

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.

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.

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

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.

What is the source of cells used in preimplantation genetic diagnosis?

Cells from an eight-cell stage embryo

Which method can be used at the DNA level to detect the presence of a specific mutation in a disease-causing allele?

DNA microarray analysis

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 methods can be used at the DNA level to test for specific mutations related to a genetic disease?

Fluorescence in situ hybridization (FISH) DNA sequencing DNA microarray analysis

Select human disorders that are inherited in an X-linked dominant manner.

Incontinentia pigmenti Rett syndrome Vitamin-D resistant rickets

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

Locus heterogeneity

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

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

Comparing someone with a genetic disease to another person in the general population, the person with the disease is more likely to have a family member with the same disease.

True

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

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

Unborn baby matches: Amniocentesis and karyotyping to detect chromosomal abnormalities Newborn baby: 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

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

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

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

a genetic disease

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

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

chorionic villus sampling

One concern associated with genetic testing and screening is the potential for misuse of private information including _________ by employers or insurance providers.

discrimination

One concern associated with genetic testing and screening is the potential for misuse of private information including ___________ by employers or insurance providers.

discrimination

Twins that share about 50% of their genetic material are called

dizygotic

Duchenne muscular dystrophy, which is inherited in an X-linked recessive manner, is caused by a mutation in the gene for ______.

dystrophin

Preimplantation genetic diagnosis is a method testing for genetic diseases in

embryos produced by in vitro fertilization

A genetic disease is spread to individuals sharing similar environmental situations.

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

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

genetic disease

A dominant genetic disorder can be caused by Blank______, 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 karyotype can be used to ______.

identify changes in chromosome number and structure associated with a disease condition

A procedure in which sperm and egg are combined outside a mother's body is called ______.

in vitro fertilization

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 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

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

Twins that are genetically identical to each other are called Blank______ twins. Multiple choice question.

monozygotic

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

monozygotic twins

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

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 of protein

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

pedigree

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

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

Chromosomal abnormalities related to genetic diseases can be detected by

producing a karyotype

Monozygotic twins ______.

share 100% of the same alleles

Dizygotic twins

share an average of 50% 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

In vitro fertilization is a procedure in which

sperm and egg are combined outside the mother's body

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

testing; screening

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