Ch 22

DNA methyltransferase.

Clinical improvement in leukemia patients has been observed when providing drugs that inhibit the enzyme DNA demethylase. histone acetyltransferase. histone methyltransferase. DNA methyltransferase. histone demethylase.

One allele is inactivated prior to birth, the other becomes inactivated early in life.

For the inherited tendency to develop retinoblastoma in the first few years of life, which correctly describes inactivation of the rb tumor-suppressor alleles by the "two-hit" model? Both alleles are inactivated by environmental factors early in life. Both alleles are inactivated prior to birth. Both alleles are eliminated by chromosomal deletions prior to birth. One allele is inactivated prior to birth, the other becomes inactivated early in life.

correlation association

If a comparison of two variables shows that they increase together, a positive ____________ is demonstrated and, if the results are statistically significant, a true ___________ between the variables is suggested.

methyltransferase

Mutations in DNA _________, an enzyme catalyzing changes that inactivate genes, have been associated with the development of acute myeloid leukemia.

methyltransferase

To potentially reverse the inactivation of tumor-suppressor genes, researchers are developing potential cancer treatments that involve inhibition of the enzyme DNA _________

detecting DNA damage in a cell.

The tumor-suppressor gene p53 has a significant role in detecting DNA damage in a cell. speeding up progress through the cell cycle. promoting the formation of new alleles through mutation. preventing apoptosis. preventing viral DNA insertion.

a. true most cancers originate from a single cell b. true c.false 80% of cancers are related to exposure to mutagens which alter the structure and expression of genes d. true

With regard to cancer cells, which of the following statements are true? a. Cancer cells are clonal, which means they are derived from a single mutant cell. b. To become cancerous, cells usually accumulate multiple genetic changes that eventually result in uncontrolled growth. c. Most cancers are caused by oncogenic viruses d. Cancer cells have lost the ability to properly regulate cell division.

c. the linkage of alleles or molecular markers on a chromosome

what is a haplotype? a. a species with one set of chromosomes b. a cell with one set of chromosomes c. the linkage of alleles or molecular markers on a chromosome d. all of the above

d. All of the above

which of the following types of epigenetic changes may promote cancer? a. DNA methylation b. covalent modification of histones c. Chromatin remodeling d. All of the above

False, most cancer cells are caused by mutations that result from environmental mutagens.

with regard to cancer cells, which of the following statements are true? C. Most cancers are caused by oncogene-carrying viruses

True

with regard to cancer cells, which of the following statements are true? b. To become cancerous, cells usually accumulate multiple genetic changes that eventually result in uncontrolled growth.

true

with regard to cancer cells, which of the following statements are true? d. Cancer cells have lost the ability to properly regulate cell division.

prevents cancerous growth.

A tumor-suppressor gene codes for a protein that normally prevents cancerous growth. increases chromosomal rearrangements. allows cells to move quickly through checkpoints in the cell division cycle. stimulates the rate of cell division. decreases the number of cancer-causing genes in the cell.

growth factor.

A signaling molecule that can promote division of cells throughout the body of a multicellular organism is called a(n) growth factor. tumor suppressor. receptor. apoptosis factor. enzyme.

a. autosomal recessive

Assuming complete penetrance, which type of inheritance pattern is consistent with the pedigree shown here? a. autosomal recessive b. autosomal dominant c. X-linked recessive d. X-linked dominant

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

A haplotype is a recombinant chromosome carrying half of the molecular markers from one parent and half from the other parent. genetic variation in which someone has half the normal number of molecular markers. phenotypic variation that is observed, on average, in half of the offspring. haploid genotype showing linkage of alleles or molecular markers along a single chromosome.

gain-of-function

A dominant genetic disorder can be caused by a ______ mutation, where the product of an altered gene has an abnormal function. loss-of-function haploinsufficient gain-of-function dominant-negative

You would probably conclude that the disease does not have a genetic component. If it were rooted primarily in genetics, it would be likely to be found in the Central American population. Of course, there is a chance that very few or none of the people who migrated to Central America were carriers of the mutant gene, but that is somewhat unlikely for a large migrating population. By comparison, you might suspect that an environmental agent that is present in south america but not present in Central America may underlie the disease. Researchers could try to search for this environmental agent (e.g., a pathogenic organism).

A particular disease occurs within a group of South American Indians. During the 1920s, many of these people migrated to Central America. In the Central American group, the disease has a genetic component. What types of further observations would you make?

amniocentesis.

A method for obtaining fetal cells in a sample of the fluid surrounding the fetus is called alpha fetoprotein sampling. amniocentesis. chorionic villus sampling. ultrasound.

locus heterogeneity.

A situation where a disease may be caused by mutations in two or more different genes is called a linkage abnormality. a pleiotropic effect. locus heterogeneity. locus heterozygosity.

genome-wide

An examination of genetic variants among many different individuals to determine if any variant is associated with a disease is called a _________-________ association study.

genome-wide

An investigation of the possible association between one or more single-nucleotide polymorphisms and a disease is called a(n) ______ association study. inheritance genome-wide sequence-specific disease population-wide

X^H X^H

Consider the accompanying 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, what is the one possible genotype that is missing among the children of Beatrice and her husband, at the right of the figure? XhXh XhY XHXH XHY XHXh

individual; population

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) ______. group of patients; individual individual; population population; individual

Though they don't change the DNA sequence, epigenetic modifications due to environmental agenets can afffect gene expression. Such changes could increase gene expression and thereby result in oncogenes, or they could inhibit the expression of tumor suppressor genes. Either type of change could contribute to cancer. For example, DNA methylation of a tumor suppressor gene could promote cancer. Epigenetic changes associated with cancer occur in somatic cells and cannot be passed from parents to offspring.

How can environmental agents that do not cause gene mutations contribute to cancer? Are epigenetic changes that are associated with cancer passed to offspring?

d. the activation of multiple oncogenes and the inactivation of multiple tumor-suppressor genes.

Most forms of cancer involve a. the activation of a single oncogene b. the inactivation of a single tumor-suppressor gene c. the activation of multiple oncogenes. d. the activation of multiple oncogenes and the inactivation of multiple tumor-suppressor genes.

C

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 A D B

c. their function is inactivated

Tumor-suppressor genes promote cancer when a. they are overexpressed b. they are expressed in the wrong cell type c. their function is inactivated d. they are expressed as the wrong stage of development.

methylation covalent chromatin

Three types of abnormal epigenetic changes that have been discovered in cancer cells are: inactivation of tumor-suppressor genes by DNA __________, changes protein-DNA associations with _________ modification of histones, and changes in nucleosome locations through ___________ remodeling.

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

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

The key feature is that affected offspring have both parents who are unaffected by the disease. The parents are heterozygous

what feature(s) of this pedigree indicate(s) autosomal recessive inheritance?

a haplotype is a linkage of alleles or molecular markers on a single chromosome

what is a haplotype?

An individual with a predisposition to develop familial breast cancer inherits only one copy of the mutant allele. Therefore, this disease show a dominant pattern of inheritance. However, for breast cancer to actually develop, the other allele must become mutant in somatic cells.

explain why familial breast cancer shows a dominant pattern of inheritance in a pedigree even though it is recessive at the cellular level.

c. gene, its linkage to other

haplotype association studies are aimed at the identification of a particular __________ based on ___________ a. chromosome, an abnormality in its structure b. chromosome, the arrangement of molecular markers c. gene, its linkage to other d. gene, chromosomal rearrangements

E2F will be active all of the time, and this will lead to cancer.

if a cell cannot make any Rb protein how will this affect the function of E2F?

A proto-oncogene is a normal cellular gene that typically plays a role in cell division. It can be altered by mutation to become an oncogene and thereby causes cancer. At the level of protein function, a proto-oncogene can become an oncogene by synthesizing too much of a protein or synthesizing the same amount of a protein that is abnormally active.

what is a proto-oncogene? What are the typical functions of the proteins encoded by them? At the level of protein function, what are the general ways that proto-oncogenes can be converted to oncogenes?

oncogene

A mutant gene that is overexpressed and contributes to the formation of cancer is termed a(n) ____________

gain-of-function

Achondroplasia is an autosomal dominant disorder caused by a mutation in the fibroblast growth factor receptor-3 gene. The mutant form of the receptor is overactive, and thus disrupts the normal signaling pathway and leads to severely shortened bones. This is an example of a(n) ___________-_________ of- mutation.

Cancer

In what disease do genetic changes lead to uncontrolled cell growth? Hemophilia Huntington Disease Severe Combined Immune Deficiency Cancer Sickle Cell Anemia

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 a linkage abnormality. locus heterogeneity. pleiotropy. locus heterozygosity.

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.

Which observations are consistent with a disease having a genetic basis? People from several different families living in a region with high levels of air pollution develop chronic obstructive pulmonary 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. People who have diets high in saturated fats are likely to develop atherosclerosis.

d. all of the above may produce an oncogene

Which of the following is a type of genetic change that may produce an oncogene? a. missense mutation b. gene amplification c. chromosomal translocation d. all of the above may produce an oncogene

monitors the state of the cell and stops progression through the cell cycle if damage is detected.

A checkpoint protein stimulates mutations that promote cell division. monitors the state of the cell and stops progression through the cell cycle if damage is detected. speeds up progress of the cell cycle so that DNA repair is accelerated. repairs double-stranded DNA breaks. digests cellular proteins in a cell that has accumulated significant DNA damage.

tumor-suppressor gene.

A gene that codes for a protein that prevents cancerous growth is a(n) tumor-suppressor gene. proto-oncogene. oncogene. mutation-promoting gene.

maintenance.

Cellular mechanisms that prevent mutations from occurring and/or prevent mutant cells from dividing or surviving are referred to as genome protection. safeguarding. maintenance. preservation. surveillance.

ethyl methyl phosphate

Mutations in the genes for enzymes that catalyze the additions or removals of ______________, _____________, or ________________ on histones have been implicated in the development of cancer.

a. chromosome walking

Which of the following is not a method used in genetic testing? a. chromosome walking b. DNA sequencing c. in situ hybridization d. DNA microarrays

a checkpoint is a point in the cell cycle at which proteins detect if the cell is in the proper condition to divide. If an abnormality such as DNA damage is detected, the checkpoint proteins will halt the cell cycle

what is a checkpoint

b. a change in chromosome number

which of the following is not a common explanation for a dominant disorder a. haploinsufficiency b. a change in chromosome number c. a gain-of-function mutation d. a dominant-negative mutation

c. preimplantation genetic diagnosis

which of the following prenatal genetic testing methods is done in conjunction with in vitro fertilization a. amniocentesis bl. chorionic villus sampling c. preimplantation genetic diagnosis d. all of the above are usually performed in conjunction with in vitro fertilization

such a mutation would keep the Ras protein in an active state and thereby promote cancerous growth. The cell-signaling pathway.

How would a mutation that prevents the ras protein from hydrolyzing GTP affect the cell-signaling pathway

The pattern of inheritance is autosomal recessive. All of the affected individuals do not have affected parents. Also, the disorder found in both males and females. If the inheritance pattern were X-linked recessive, individual III-1 would have to have an affected father, which she does not.

Hurler syndrome is due to a mutation in a gene that encodes a protein called alpha-L-iduronidase. This protein functions within lysosomes as an enzyme that breaks down mucopolysaccharides (a type of polysaccharide that has many acidic groups attached). When this enzyme is defective, excessive amounts of the mucopolysaccharides dermatan sulfate and heparan sulfate accumulate within the lysosomes, especially in liver cells and connective tissue cells. This accumulation leads to symptoms such as an enlarged liver and spleen, bone abnormalities, corneal clouding, heart problems, and severe neurological problems. The following pedigree contains three individuals affected with the Hurler syndrome, indicated with black symbols. Based on this pedigree, does this syndrome appear to follow autosomal recessive, autosomal dominant, X-linked recessive, or X-linked dominant inheritance? Explain your reasoning.

e. both a and b

The underlying cause(s) of epigenetic changes associated with cancer may be a. mutations in genes that encode chromatin-modifying proteins b. environmental agents that alter the function of chromatin-modifying proteins c. mutations in genes that encode proteins that directly accelerate cell growth d. all of the above e. both a and b

gain-of-function dominant-negative

There are three common explanations for autosomal dominant disorders: 1. Haploinsufficiency; 2. __________-of-__________ mutations; and 3. Dominant-________ mutations.

Dominant-negative mutations Haploinsufficiency Gain-of-function mutations

What are the three common explanations for autosomal dominant disorders? Aneuploidy Dominant-negative mutations Haploinsufficiency Dominant-positive mutations Loss-of-function mutations Gain-of-function mutations

Autosomal dominant

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? X-linked recessive Autosomal dominant Autosomal recessive X-linked dominant

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? X-linked recessive Autosomal recessive X-linked dominant Autosomal dominant

Autosomal recessive

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? X-linked dominant X-linked recessive Autosomal recessive Autosomal dominant

Autosomal recessive

What is the most likely mode of inheritance of the trait exhibited in this pedigree? X-linked recessive Autosomal recessive X-linked dominant Autosomal dominant

DNA microarray analysis

Which method can be used at the DNA level to detect the presence of a specific mutation in a disease-causing allele? Enzyme activity assay Western blot DNA microarray analysis

The trait occurs in the same frequency in both males and females. Two affected individuals must have affected children. An affected offspring can have two unaffected parents.

Which of the following features are characteristic of autosomal recessive inheritance? Two unaffected heterozygotes have on average 50% affected children. An affected individual must have at least one affected parent. Males are affected more frequently than females. The trait occurs in the same frequency in both males and females. Two affected individuals must have affected children. An affected offspring can have two unaffected parents.

b. the disorder can spread to individuals sharing similar environments

Which of the following would not be consistent with the idea that a disorder has a genetic component? a. The disorder is more likely to occur among an affected person's relatives than in the general population b. the disorder can spread to individuals sharing similar environments c. the disorder tends to develop at a characteristic age. d. a correlation is observed between the disorder and a mutant gene.

Test for excess phenylalanine indicating phenylketonuria (PKU)

Which of these is a common example of widespread genetic screening of newborns to identify certain disorders? Enzyme assay for Tay-Sachs allele carrier status Amniocentesis and karyotyping Enzyme assay for Gaucher disease carrier status Test for excess phenylalanine indicating phenylketonuria (PKU)

Males die at an early stage of development

Which statement is true of X-linked dominant disorders such as Rett syndrome and Aicardi syndrome? Females die at an early stage of development Both males and females die at an early stage of development Males die at an early stage of development

DNA methylation Chromatin remodeling Covalent modification of histones

Which types of abnormal epigenetic changes have been observed in cancer cells? DNA methylation Chromatin remodeling Covalent modification of histones Relocation of enhancers to regions near proto-oncogenes Mutations in genes coding for tumor suppressors

C

he 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? B D C A

has accumulated genetic changes that allow it to grow uncontrollably.

A cancer cell is a cell that has accumulated genetic changes that allow it to grow uncontrollably. no longer divides because it receives fewer signals to initiate cell division. divides more frequently than other cells, even though both types of cells have similar genetic compositions. no longer divides because most of its genes have been silenced.

haploinsufficiency

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. gain-of-function mutation dominant-negative mutation haploinsufficiency

oncogene.

A gene that promotes cancer is called a(n) proto-oncogene. oncogene. tumor-activator gene. tumor-suppressor gene. cell-cycle inhibitor gene.

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

Amniocentesis is a procedure for obtaining fetal cells in a sample from the fluid surrounding the fetus. testing the mother's blood for a protein associated with spina bifida. obtaining a sample of the fetal part of the placenta. testing the mother's blood for an excess of phenylalanine, indicating phenylketonuria (PKU).

1. the disease-causing allele had its origin in a single individual known as a founder, who lived many generations ago. Since that time, the allele has spread throughout portions of the human population 2. When the disease-causing allele originated in the founder, it occurred in a region with a particular haplotype. The haplotype is not likely to have changed over the course of several generations if the disease-causing allele and markers in this region are very close together.

Describe the two assumptions that underlie the identification of disease causing alleles via haplotypes

linkage disequilibrium.

If alleles and molecular markers are associated with each other at a frequency greater than expected by random chance, the situation is described as inhibition of recombination. linkage disequilibrium. linkage fixation. locus heterogeneity. locus homogeneity.

converting a normal cell into a malignant cell.

In cancer biology, transformation is the process of inducing mutations in a somatic cell. halting the growth of a cancer cell. converting a normal cell into a malignant cell. stimulating the formation of a benign growth.

d. in all of the above.

Personalized medicine may be used a. to characterize types of tumors b. to predict the outcome of certain types of cancers c. to determine the proper dosage of drugs d. in all of the above.

BB without 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. Consider the couple that is surrounded by the red circle. Of their possible children, what phenotype and marker combination is missing? BB without Huntington disease CC with Huntington disease BB with Huntington disease BC without Huntington disease

One possible category of durgs would be GDP analogues (i.e., compounds whose structures resemble that of GDP). Perhaps you could find a GDP analogue that binds to the Ras protein and locks it in the inactive conformation. One way to test the efficacy of such a drug would be to incubate the drug with a type of cancer cell that is known to have an overactive Ras protein, and then plate the cells on solid media. If the drug locked the Ras protein in the inactive conformation, it should inhibit the formation of malignant growth or malignant foci. There are possible side effects of such drugs. First, they might block the growth of normal cells, because Ras protein plays a role in normal cell proliferation . Second (as you might know from a cell biology course), there are many GTP/GDP-binding proteins in cells, and the drugs could somehow inhibit cell growth and function by interacting with these proteins.

The codon change (Gly-12 to Val-12) in human rasH that converts it to oncogenic rasH has been associated with many types of cancers. For this reason, researchers would like to develop drugs to inhibit oncogenic rasH. Based on your understanding of the Ras protein, what types of drugs might you develop? In other words, what would be the structure of the drugs, and how would they inhibit Ras protein? How would you test the efficacy of the drugs? What might be some side effects?

haplotype

The linkage of alleles or molecular markers along a single chromosome is called a(n) _____________.

testing; screening

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. analysis; testing screening; testing testing; screening diagnosis; screening

The bcr gene is expressed in white blood cells. This translocation causes the abl gene to be under the control of the bcr promoter. The abnormal expression of abl in white blood cells causes leukemia.

Why does this translocation cause leukemia rather than cancer in a different tissue type, such as the lung?

When a disease-causing allele affects a trait, it is causing a deviation from normality, but the gene involved is not usually the only gene that governs the trait. For example, an allele causing hemophilia prevents the normal blood-clotting pathway from operating correctly. It follows a simple mendelian pattern because a single gene affects the phenotype. Even so, it is known that normal blood clotting is due to the actions of many genes.

explain, at the molecular level, why human genetic diseases often follow simple mendelian patterns of inheritance, whereas most normal traits, such as the shape of your nose or the size of your head, are governed by multiple gene interactions.

Yes, because E2F is not inhibited

The rb gene encodes a protein that inhibits E2F, a transcription factor that activates several genes involved in cell division. Mutations in rb are associated with certain forms of cancer, such as retinoblastoma. Under each of the following conditions, would you expect cancer to occur? C. Both copies of the rb gene are defective; one copy of the E2F gene is defective

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 X-linked dominant X-linked recessive Autosomal dominant

An affected individual has at least one affected parent. 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? Males are affected more frequently than females. An affected offspring can have two unaffected parents. An affected individual has at least one affected parent. The trait occurs in both males and females.

there is a 50% chance that this couple will have an affected child

Marfan Syndrome is due to a mutation in a gene that encodes a protein called fibrillin-1. The syndrome is inherited as a dominant trait. The fibrillin-1 protein is the main constituent of extracellular microfibrils. These microfibrils can exist as individual fibers or associate with a protein called elastin to form elastic fibers. People with the disorder tend to be unusually tall with long limbs, and they may have defects in their heart valves and aorta. Let's suppose a phenotypically unaffected woman has a child with a man who has Marfan syndrome. A. What is the probability this child will have the disease?

True

with regard to cancer cells, which of the following statements are true? A. Cancer cells are clonal, which means they are derived from a single mutant cell.

Conversion of a proto-oncogene can occur by missense mutation, gene amplification, chromosomal translocation and viral integration. Examples are given in Table 22.6. The genetic changes are expected to increase the amount of the encoded protein or alter its function in a way that makes it more active.

Describe the types of genetic changes that commonly convert a proto oncogene to an oncogene. Give three examples. Explain how the genetic changes are expected to alter the activity of the gene product.

The person is born with two active copies of the rb allele; separate mutation events are required to inactivate each of these alleles.

For the non-inherited development of retinoblastoma, which correctly describes inactivation of the rb tumor-suppressor alleles by the "two-hit" model? The person is born with two inactive copies of the rb allele; followed by two more mutations in the allele causing further inactivation. The person is born with two active copies of the rb allele; separate mutation events are required to inactivate each of these alleles. The person is born with two inactive copies of the rb allele. The person is born with one inactive copy of the rb allele; a mutation inactivates the second rb allele

We need to apply the binomial expansion equation (see ch 3 for a description of this equation) with n=5, x=1, p=0.25, q=0.75. The answer is 0.393 or 39.6%

Gaucher disease (type I) is due to a defect in a gene that encodes a protein called acid beta glucosidase. This enzyme plays a role in carbohydrate metabolism within lysosomes. The gene is located on the long arm of chromosome 1. People who inherit two defective copies of this gene exhibit Gaucher disease, the major symptoms of which include an enlarged spleen, bone lesions, and changes in skin pigmentation. Let's suppose a phenotypically unaffected woman, whose father had gaucher disease, has a child with a phenotypically unaffected man, whose mother had gaucher disease. c. If this couple has five children, what is the probability that one of them will have gaucher disease and four will be phenotypically unaffected?

We use the product rule. The odds of having an unaffected child are 50%. So, 0.5^3 = 0.125 or a 12.5% chance of having three unaffected offspring.

Marfan Syndrome is due to a mutation in a gene that encodes a protein called fibrillin-1. The syndrome is inherited as a dominant trait. The fibrillin-1 protein is the main constituent of extracellular microfibrils. These microfibrils can exist as individual fibers or associate with a protein called elastin to form elastic fibers. People with the disorder tend to be unusually tall with long limbs, and they may have defects in their heart valves and aorta. Let's suppose a phenotypically unaffected woman has a child with a man who has Marfan syndrome. b. what if this couple has three children, what is the probability that none of them will have marfan syndrome?

haploinsufficiency

The phenomenon in which a person has only a single functional copy of a gene which is not enough to produce a normal phenotype is called _____________.

No, because E2F is inhibitied

The rb gene encodes a protein that inhibits E2F, a transcription factor that activates several genes involved in cell division. Mutations in rb are associated with certain forms of cancer, such as retinoblastoma. Under each of the following conditions, would you expect cancer to occur? a. One copy of the rb gene is defective; both copies of the E2F gene are functional.

The key feature is that affected offspring have an affected parent.

what feature(s) of this pedigree indicate(s) autosomal dominant inheritance?

1. Amniocentesis and karyotyping to detect chromosomal abnormalities 2. Test for excess phenylalanine demonstrating phenylketonuria (PKU) 3. Test for carrier status if one belongs to a family with a history of a specific disease

Match the life stage on the left to the type of screening on the right that would be used to detect a genetic disease. 1. Fetus _______________ 2. Newborn baby __________ 3. Adult _______________

yes, because E2F is not inhibited

The rb gene encodes a protein that inhibits E2F, a transcription factor that activates several genes involved in cell division. Mutations in rb are associated with certain forms of cancer, such as retinoblastoma. Under each of the following conditions, would you expect cancer to occur? b. Both copies of the rb gene are defective; both copies of the E2F gene are functional

b. an oncogene

a mutant gene that promotes cancer when it is over expressed is called a. a tumor-suppressor gene b. an oncogene c. both a and b d. neither a nor b

No, because there is no E2F

The rb gene encodes a protein that inhibits E2F, a transcription factor that activates several genes involved in cell division. Mutations in rb are associated with certain forms of cancer, such as retinoblastoma. Under each of the following conditions, would you expect cancer to occur? d. Both copies of the rb gene and the E2F gene are defective

X-linked dominant

What is the inheritance pattern for a trait that is more likely to occur in females when it is lethal to males? Autosomal recessive Autosomal dominant X-linked recessive X-linked dominant

X-linked recessive

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? Autosomal dominant X-linked dominant X-linked recessive Autosomal recessive

b. is caused by mutations in two or more different genes.

locus heterogeneity means that a genetic disorder a. has a heterogeneous phenotype b. is caused by mutations in two or more different genes. c. involves a structural change in multiple chromosomes d. is inherited from both parents.

d. both a and b are functions of normal tumor-suppressor genes.

normal (nonmutant) tumor-suppressor genes often function a. as negative regulators of cell division b. in the maintenance of genome integrity c. in the stimulation of cell division d. both a and b are functions of normal tumor-suppressor genes.

here are a few possible answers: dwarfism occurs in people and dogs. Breeds like the dachshund and basset hound are examples of dwarfism in dogs. There are diabetic people and mice. There are forms of inherited obesity in people and mice. Hip dysplasia affects people and dogs.

Figure 22.1 illustrates albinism in two different species. Describe two other genetic disorders found in both humans and animals.

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? Autosomal dominant X-linked dominant X-linked recessive Autosomal recessive

From the punnet square we can see that there is a 1/4 chance of producing a homozygous with both normal copies of the gene.

Gaucher disease (type I) is due to a defect in a gene that encodes a protein called acid beta glucosidase. This enzyme plays a role in carbohydrate metabolism within lysosomes. The gene is located on the long arm of chromosome 1. People who inherit two defective copies of this gene exhibit Gaucher disease, the major symptoms of which include an enlarged spleen, bone lesions, and changes in skin pigmentation. Let's suppose a phenotypically unaffected woman, whose father had gaucher disease, has a child with a phenotypically unaffected man, whose mother had gaucher disease. b. what is the probability that this child will have two normal copies of this gene?

Because a person must inherit two defective copies of this gene and it is known to be on chromosome 1, the mode of transmission is autosomal recessive. Both parents must be heterozygous because they had to have one affected parent (who transmitted the mutant allele to them) and their phenotypes are unaffected ( so they must have recieved the normal allele from their other parent). Because both parents are heterozygotes, there is a 1/4 chance of producing an affected child (a homozygote) with gaucher disease. If we let G represent the nonmutant allele and g the mutant allele, we obtain the following punnet square G | g G | GG | Gg g | Gg | gg

Gaucher disease (type I) is due to a defect in a gene that encodes a protein called acid beta glucosidase. This enzyme plays a role in carbohydrate metabolism within lysosomes. The gene is located on the long arm of chromosome 1. People who inherit two defective copies of this gene exhibit Gaucher disease, the major symptoms of which include an enlarged spleen, bone lesions, and changes in skin pigmentation. Let's suppose a phenotypically unaffected woman, whose father had gaucher disease, has a child with a phenotypically unaffected man, whose mother had gaucher disease. A. What is the probability that this child will have the disease?

a higher level of association between a disease allele and a molecular marker than would be expected by chance.

Linkage disequilibrium is a situation where a disease may be caused by mutations in two or more different genes. a higher level of association between a disease allele and a molecular marker than would be expected by chance. a tendency for a disease allele and a molecular marker to be separated by recombination. an unstable situation involving significant chromosome breakage.

The 13 babies have acquired a new mutation. In other words, during spermatogenesis or oogenesis, or after the egg was fertilized, a new mutation occurred in the fibroblast growth factor gene. These 13 individuals have the same chances of passing the mutant allele to their offspring as the 18 individuals who inherited the mutant allele from a parent. The chance is 50%

Achondroplasia is a rare form of dwarfism caused by an autosomal dominant mutation that affects the gene that encodes a fibroblast growth factor receptor. Among 1,422,000 live births, the number of babies born with achondroplasia was 31. Among those 31 babies, 18 of them had one parent with achondroplasia. The remaining babies had two unaffected parents. How do you explain those 13 babies, assuming that the mutant allele has 100% penetrance? What are the odds that these 13 individuals will pass this mutant gene to their offspring?

transformation.

The process of converting a normal cell into a malignant cancer cell is called transformation. transduction. conjugation. transfection.

malignancy.

A series of genetic changes, involving oncogene activation and tumor-suppressor gene inactivation, leads to apoptosis. formation of a benign growth. malignancy. inhibition of the cell cycle.

signaling molecule that can stimulate cells throughout the organism's body to divide.

A growth factor is a signaling molecule that can stimulate cells throughout the organism's body to divide. molecule that promotes programmed cell death through apoptosis. molecule that can inhibit cell division. protein on the surface of the cell that receives signals to increase the cell division rate.

checkpoint protein.

A protein that stops progression through the cell cycle if the cell has DNA or chromosomal irregularities is called a(n) transition regulator. transcriptional activator. inhibitory protein. checkpoint protein. growth factor.

has inherited an increased susceptibility to develop cancer.

An individual who is heterozygous for a defect in a tumor-suppressor gene has inherited an increased susceptibility to develop cancer. will definitely develop cancer during their lifetime. has inherited a protective mechanism that will prevent cancer.

the chromosome carrying the tumor-suppressor gene can be lost from the cell.

Aneuploidy is a mechanism for losing the function of a tumor-suppressor protein because the chromosome carrying the tumor-suppressor gene can be lost from the cell. translocation brings the tumor-suppressor gene into a transcriptionally-inactive area of another chromosome. a mutation in the promoter region prevents RNA polymerase from binding. methylation of cytosines in CpG islands near the promoter can inhibit transcription.

1. missense mutation missense mutations in the ras gene can change the structure of the ras protein to make it permanently active. 2. gene amplification increasing copies of a gene result in more protein. example: amplification of c-myc in leukemia 3. chromosomal translocation chronic myelogenous leukemia (CML) is correlated with the Philadelphia chromosome. Chromosome 22 shortens due to an abnormal crossover with chromosome 9. 4. viral integration certain viruses integrate into host DNA as part of their life cycle. This can cause activation of a cellular proto-oncogene from the viral proto-oncogene from the viral promoter or enhancer. Example, Rous sarcoma virus (RSV).

Describe the types of genetic changes that commonly convert a proto-oncogene into an oncogene. Give three examples. Explain how the genetic changes are expected to alter the activity of the gene product.

chromosomal translocation.

Ewing's sarcoma is a cancer of the bone and soft tissues where a new transcription factor is produced from the fusion of the coding regions of two different proteins. The ews gene of chromosome 22 is joined to the fli1 gene of chromosome 11. Neither the ews nor the fli1 gene individually causes cancer. This change from proto-oncogene to oncogene occurred as a result of viral DNA integration in an adjacent region. chromosomal translocation. gene amplification. a nonsense mutation. a missense mutation.

Mutation; Division or survival of mutant cells

Genome maintenance includes cellular mechanisms that prevent which two processes? Mutation; Repair of double-stranded DNA breaks Mutation; Division or survival of mutant cells Recombination; DNA replication Repair of double-stranded DNA breaks; Division or survival of mutant cells Recombination; Division or survival of mutant cells

positive correlation.

If an increase in DNA methylation of a gene is associated with an increase in severity of a specific disease, these two variables show a(n) cause-and-effect relationship. negative correlation. independent variation. positive correlation.

Changes in chromosome number and unbalanced changes in chromosome structure tend to affect phenotype because they create and imbalance of gene expression. For example, in Down syndrome, there are three copies of chromosome 21 and therefore three copies of all the genes on that chromosome. The result is a relative overexpression of genes that are located on chromosome 21 compared to the other chromosomes. Balanced translocations and inversions often lack phenotypic consequences because the total amount of genetic material is not altered, and the level of gene expression is not significantly changed.

In general, why do changes in chromosome structure or number tend to affect an individual's phenotype? Explain why some changes in chromosome structure, such as reciprocal translocations, do not.

heterozygous for the autosomal dominant

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 recessive hemizygous for the X-linked recessive hemizygous for the X-linked dominant heterozygous for the autosomal dominant homozygous for the autosomal dominant

heterozygous for a defect in a tumor-suppressor gene.

Most individuals who are born with an inherited form of cancer susceptibility are heterozygous for a defect in a tumor-suppressor gene. heterozygous for a defect in a proto-oncogene. homozygous for a defect in a tumor-suppressor gene. homozygous for a defect in a proto-oncogene.

high

The development of cancer could be promoted if an abnormally ___________ level of methylation occurred at CpG islands near the start site of a tumor-suppressor gene.

aneuploidy

The loss of a chromosome carrying a tumor-suppressor gene is an example of a way of losing the function of this gene through chromosomal translocation. aneuploidy. introduction of an early stop codon in the coding sequence. methylation of cytosines near the promoter region.

Creation of a new transcription factor through the fusion of chromosomal segments from two different chromosomes

Which change from proto-oncogene to oncogene occurred by chromosomal translocation? Increase in the number of copies of the gene for a growth factor receptor in breast cancer cells Substitution of valine for glycine at position 12 in the amino acid sequence of the rasH protein Decreased transcription of the tumor-suppressor gene p53 following the integration of DNA from the HTLV-1 retrovirus into T cells Creation of a new transcription factor through the fusion of chromosomal segments from two different chromosomes Increase in the number of copies of the cdk4 gene in its original location on chromosome 12

p53

Which gene plays a significant role in detecting DNA damage in a cell? p53 myc e2f ras rb

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

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 Western blot Enzyme activity assay

A series of successive gene changes occurs, involving oncogene activation and inactivation of tumor-suppressor genes.

Which of the following accurately describes the genetic change(s) leading to malignancy? A single genetic change occurs, involving activation of an oncogene. A series of successive gene changes occurs, involving oncogene activation and inactivation of tumor-suppressor genes. A single genetic change occurs, involving inactivation of a tumor-suppressor gene. Multiple, simultaneous gene changes occur, involving oncogene activation and tumor-suppressor gene inactivation.

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

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 often have brothers with the disease. An affected individual must have an affected parent. Males and females are equally likely to have the disease. Males are more likely to be affected than females.

hypermethylation inhibits the expression of a tumor suppressor gene

Which of the following is an epigenetic change that would likely lead to cancer? hypermethylation inhibits the expression of a tumor suppressor gene hypermethylation increases the expression of a tumor suppressor gene hypermethylation increases the expression of a proto-oncogene gene

Preimplantation genetic diagnosis

Which of the following prenatal genetic testing methods is done in conjunction with in vitro fertilization? a. Amniocentesis b. Chorionic villus sampling c. Preimplantation genetic diagnosis d. All of the above