CH 24

Haplotypes are relatively stable from one generation to the next because

* crossing over is unlikely to occur for molecular markers that are close to each other * mutations that would change the haplotype are rare

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

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

Which observations are consistent with a disease having genetic basis?

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

To prevent cells with damage DNA from dividing, the tumor-suppressor protein p53 can

*stimulate the expression of the p21 gene to inhibit the G1 to S transition of the cell cycle *activate genes involved with DNA repair *initiate apoptosis

molecular profiling is useful because

*tumors with similar appearances can be distinguished by differences in the genetic expression patters *drugs can be developed that will specifically target proteins encoded by cancer-causing gene mutations

Which observations are consistent with a disease having a genetic basis? (Check all that apply!)

-The sleep disorder called narcolepsy has been related to an allele for a faulty neural receptor in dogs. Some humans also suffer from narcolepsy. -A cancerous growth of immature nerve cells called neuroblastoma is associated with a deletion in a specific region of chromosome 11. -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 malignant tumor

-can form secondary tumors after spreading to other locations -can invade nearby healthy tissue -has cells with cancerous mutations leading to uncontrolled growth

Acutely transforming viruses

-induce tumors rapidly in animals -efficiently transform cells in culture

Which of the following are characteristics of a sex linked recessive inheritance pattern. (Check all that apply!)

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

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

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

There are three common explanations for autosomal dominant disorders

1. Haploinsufficiency 2. Gain-of-function mutation 3. Dominant-negative mutations

Order of events in the normal pathway by which growth factors stimulate cell division

1. a growth factor binds to a specific receptor on the surface of a cell 2. a transduction pathway activities intracellular protein to amplify the signal 3. genes coding for proteins that control cell division are activated

Tay-Sachs disease is inherited with an autosomal recessive allele that leads to a defect in the enzyme hexosaminidase. Rank the amount of enzymatic activity that would be detected in a biochemical assay on cells from patients of these genotypes. Start with the least enzymatic activity

1. homozygous recessive 2. heterozygous 3. homozygous dominant

In a disease that has a single gene, the concordance among monozygotic twins should be

100%

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 pathways and leads to severely shortened bones. This is an example of a

Gain-of-function mutation

What is the difference between genetic testing and genetic screening?

Genetic testing is concerned more with individuals and genetic screening is concerned with populations

Genome maintenance includes cellular mechanisms that prevent which two processes?

Mutation Division or survival of mutant 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

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

X-linked recessive

Linkage disequilibrium is

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

A benign tumor is

a localized growth with a precancerous genetic change

Many genetic disorders exhibit a characteristic ______ of ____ which refers to the time at which the disease appears

age of onset

The two common ways of obtaining cellular material from a fetus for genetic testing are

amniocentesis and chorionic villus sampling

The loss of a chromosome carrying a tumor-suppressor gene is an example of a way of losing the function of this gene through

aneuploidy

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

chorionic villus sampling

Most cancer cells are descendants of an original cell that acquired genetic changes. Therefore, cancerous growths are considered to be ___ in origin.

clonal

The _____ of a trait refers to the degree to which it is inherited. Geneticists evaluate it by calculating the percentage of twin pairs in which both twins expressed the trait

concordance

In cancer biology, transformation is the process of

converting a normal cell into a malignant cell

which change from proto-oncogene to oncogene occurred by chromosomal translocation?

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

A mutation that alters the gene product in a way that acts antagonistically to the normal gene product is called a

dominant-negative mutation

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

haplotype

Most individuals that are born with an inherited form of cancer susceptibility are

heterozygous for a defect in a tumor-suppressor gene

The loss of function of a normal allele when the other allele for that gene was already inactivated is called

loss of heterozygosity

Cancer cells can migrate to other parts of the body and cause secondary tumors. This property is called

metastatic

The term that indicates that cancer has begun to migrate to other parts of the body is ____

metastatic

Amniocentesis is a procedure for

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

A gene that promotes cancer is called a(n)

oncogene

A mutant gene that is overexpressed and contributes to the formation of cancer is termed an

oncogene

A tumor-suppressor gene codes for a protein that normally

prevents cancerous growth

A normal, nonmutated gene that has the potential to become an oncogene is called a

proto-oncogene

Monozygotic twins

share 100% of the same alleles

In vitro fertilization is a procedure in which

sperm and egg are combined outside the mother's body

Pharmacogenetics is the

study of genetic variations that cause different responses to drugs

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

true

Personalized medicine is the

use of information about a patient's genotype and other clinical data to select an individualized treatment

Cancer cells may carry gain-of-function mutations that increase the activity of an oncogene. In which of the following ways could the expression of the protein encoded by the oncogene be altered by this type of mutation?

*The amount of protein produced from the oncogene is significantly increased *The protein is expressed in a cell type where it is not normally found *The structure of the protein is altered so that it is overly active

You are trying to identify the mutant gene responsible for a human disease. You have performed haplotype association, which has identified a short chromosomal region associated with the disease. which are the steps to identify the gene

1. use published DNA sequences to identify the 5-10 genes located in the chromosomal region 2. examine databases and literature to consider the biological function of a candidate genes in the region 3. sequence the candidate genes from both affected and unaffected individuals

Which of the following are detected when visualizing the chromosomes of caner cells by microscopy?

Changes in the number of chromosomes abnormalities in chromosome structure

A series of events leading to programmed cell death is called

apoptosis

A disease that is lethal only in the homozygous condition is most likely which of the following?

autosomal recessive

The disease hemophilia is caused by a deficiency in any of the 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

Cancerous growths are clonal in origin because cancel cells

originate from a single cell that has accumulated genetic changes during cell division

In cells with damaged DNA, DNA repair genes are activated by

p53

A disease-causing agent composed entirely of protein is termed a

prion

A growth factor is a

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

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

autosomal recessive

In what disease do genetic changes lead to uncontrolled cell growth

cancer

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 protein that stops progression through the cell cycle if the cell has DNA or chromosomal irregularities is called a

checkpoint protein

The tumor-suppressor gene p53 has a significant role in

detecting DNA damage in a cell