UNIT 2 QUESTIONS

What are three examples of prenatal diagnostic studies? Drug-sensitivity testing Amniocentesis Preimplantation genetic testing (PGT) Chorionic villus sampling (CVS) Microscopy of cervical mucosa

2,3,4 Correct! Chorionic villus sampling (CVS), amniocentesis, and preimplantation genetic testing (PGT) are examples of prenatal diagnostic studies and are performed in vitro. CVS is a form of genetic testing that provides genetic information found in utero and is usually performed between weeks 11 and 14 of pregnancy. An amniocentesis is a form of genetic testing that evaluates amniotic fluid and is usually performed during the second trimester, between weeks 15 and 20 of pregnancy. PGT is performed on the embryo prior to implantation.

Which type of genetic disease affects males more frequently than females? 1 Autosomal recessive 2 Autosomal dominant 3 Sex-linked recessive 4 Sex-linked dominant

3. Since males have only one X and one Y, if the affected chromosome has the illness, it will be expressed.

Recurrence risk in multifactorial diseases is higher if more than one family member is affected. lower if the disease is more severe in the proband. higher if the proband is the more commonly affected sex. rapidly increased when more distant relatives are affected.

ANS: 1 First, the recurrence risk becomes higher if more than one family member is affected. For example, the sibling recurrence risk for a ventricular septal defect (VSD), a type of congenital heart defect) is 3% if one sibling has had a VSD but increases to approximately 10% if two siblings have had VSDs. 2. Second, if the expression of the disease in the proband is more severe, the recurrence risk is higher. This is again consistent with the liability model because a more severe expression indicates that the affected individual is at the extreme tail end of the liability distribution (see Figure 5-2). His or her relatives are thus at a higher risk for inheriting disease genes. 3. Third, the recurrence risk is higher if the proband is of the less commonly affected sex. This is because an affected individual of the less susceptible gender is usually at a more extreme position on the liability distribution. 4. Fourth, the recurrence risk for the disease usually decreases rapidly in more remotely related relatives (Table 5-2). Whereas the recurrence risk for single-gene diseases decreases by 50% with each degree of relationship (e.g., an autosomal dominant disease has a 50% recurrence risk for siblings, 25% for uncle-nephew relationships, 12.5% for first cousins), it decreases much more quickly for multifactorial diseases.

Which statement by the nurse indicates an accurate understanding of epigenetics and cancer? "Hypomethylation of the promoter region of the RB1 gene is often observed in retinoblastoma." "Hypomethylation increases as tumors progress from benign neoplasms to malignancy." "Hypomethylation of specific subgroups of miRNAs is associated with tumorigenesis." "Hypomethylation occurs when HDAC inhibitors are administered for cancer."

ANS: 2 Tumor cells typically exhibit hypomethylation (decreased methylation), which can increase the activity of oncogenes. 1. Hypermethylation of the promoter region of the RB1 gene is often seen in retinoblastoma. 3. Hypermethylation of specific subgroups of micoRNAs is associated with tumorigenesis. 4. Another class of drugs, histone deacetylase (HDAC) inhibitors, counteracts the removal of acetyl groups from histone proteins which can silence the activity of tumor-suppressor genes.

Which information is correct regarding relative risk? Relative risk indicates the number of new cases of a disease in a specific time period. proportion of a population with a disease at one time point. chance of developing a disease relative to an exposure. ability of a causative factor to produce a disease.

ANS: 3 Relative risk is the ratio of the incidence a disease in those exposed to a risk factor to the incidence of the disease in those not exposed to the risk factor. This is a common indicator of the effects of specific risk factors. 1. The number of new cases of a disease in a specific time period is the incidence. 2. The proportion of a population with the disease at one time point is the prevalence. 4. Pathogenicity describes the ability of a particular disease agent to produce a disease.

Which statement made by the nurse indicates an accurate understanding of breast cancer? "BRCA1 is on chromosome 13." "If a woman has one affected first-degree relative, then her risk of developing breast cancer triples." "Alterations in the kallikrein-kinin system increases the risk for breast cancer." "Women who inherit a mutation in BRCA2 experience a 50% to 80% lifetime risk of developing breast cancer."

ANS: 4 Genes responsible for this form of breast cancer have been mapped to chromosomes 17 (BRCA1) and 13 (BRCA2). It is possible to test each of these genes for inherited cancer-causing mutations. Women who inherit a mutation in BRCA1 or BRCA2 experience a 50% to 80% lifetime risk of developing breast cancer. 1. BRCA1 is on chromosome 17. Genes responsible for this form of breast cancer have been mapped to chromosomes 17 (BRCA1) and 13 (BRCA2). 2. If a woman has one affected first-degree relative, her risk of developing breast cancer doubles. 3. Kallikrein-kinin system is involved with blood pressure, not breast cancer.

Which statement is most correct regarding miRNAs? miRNAs result from the attachment of a methyl group to a cytosine base, followed by a guanine base. enhance X-inactivation, silencing genes on the X chromosome. become the hereditary transmission of epigenetic changes to successive generations. are short nucleotides derived from introns of protein-coding genes.

ANS: 4 Micro-ribonucleic acids (miRNAs or miRs ) are short nucleotides derived from introns of protein coding genes or transcribed as independent genes from regions of the genome. Micro-ribonucleic acids (miRNAs or miRs) are encoded by short DNA sequences (approximately 22 nucleotides) located in introns of genes or transcribed from noncoding DNA located between genes. 1. DNA methylation results from attachment of a methyl group to a cytosine base that is followed by a guanine base (a "CpG dinucleotide"). 2. DNA methylation is a key component of X-inactivation, the transcriptional silencing of genes on the X chromosome. 3. The hereditary transmission of epigenetic changes to successive generations has been termed epigenetic transgenerational inheritance.

Type 2 diabetes is caused by an absence of insulin. usually involves a gene identified as HLA. is commonly associated with HLA associations or autoantibodies. is often treated with lifestyle modification including diet and exercise.

ANS: 4 This type of diabetes is highly associated with increased BMI and obesity, thus weight loss is one goal of therapy. Dietary modifications can aid weight loss and reduce total glucose load. 1. Type 2 diabetes is highly associated with obesity and an increase in BMI. Obesity is most commonly defined as a body mass index (BMI) greater than 30. Obesity increases insulin resistance. Type 2 diabetes produces insulin resistance; cells have difficulty using the insulin that is produced. Type 1 diabetes is characterized by destruction of pancreatic beta cells and reduction/absence of insulin. 3. The most significant gene identified thus far is TCF7L2, which encodes a transcription factor involved in the secretion of insulin. A variant of TCF7L2 is associated with a 50% increased risk of developing type 2 diabetes. Neither HLA associations nor autoantibodies are seen commonly in this form of diabetes.

Which pathophysiologic process is occurring in a person with Beckwith-Wiedemann syndrome? Missing chromosome 15 Missing gene product Downregulation of IGF2 Extra copies of active IGF2

ANS: 4 While upregulation, or extra copies, of active IGF2 causes overgrowth in Beckwith-Wiedemann syndrome, downregulation of IGF2 causes the diminished growth seen in Russell-Silver syndrome. 1. A well-known disease example of imprinting is associated with a deletion of about 4 million base pairs (Mb) of the long arm of chromosome 15. If it is from the father it is called Prader-Willi; if it is from the mother it is called Angelman syndrome. 2. In contrast to Prader-Willi and Angelman syndromes, which are produced by a missing gene product, Beckwith-Wiedemann syndrome is caused, in part, by overexpression of a gene product. 3. While upregulation, or extra copies, of active IGF2 causes overgrowth in Beckwith-Wiedemann syndrome, downregulation of IGF2 causes the diminished growth seen in Russell-Silver syndrome.

Which is a common characteristic of Beckwith-Wiedemann syndrome? A. Omphalocele B. Leg-length discrepancy C. Hyperglycemia D. Obesity

ANS: A Characteristics of Beckwith-Wiedemann syndrome include large size for gestational age, hypoglycemia, large tongue, creases on the earlobe, and omphalocele (birth defect of infant's intestines). Leg-length discrepancy is characteristic of Russell-Silver syndrome. Hypoglycemia, not hyperglycemia, is characteristic of Beckwith-Wiedemann syndrome. Obesity is a characteristic of Prader-Willi syndrome.

Although the mother is staying with the child after surgical correction, her husband comes to visit and brings their other child. This child has Prader-Willi syndrome. This disease is an example of imprinting. trisomy. hypermethylation. nondisjunction.

ANS: A Imprinting is a process of gene silencing in which genes are silenced depending on which parent transmits them. Prader-Willie is inherited from the father and is a deletion of a portion of the long arm of chromosome 15. Trisomy is the duplication of chromosome material, whereas Prader-Willie is a monosomy. Methylation is one of several epigenetic mechanisms that cells use to control gene expression. Hypermethylation is associated with tumor production. Nondisjunction in an error in which homologous chromosomes or sister chromatids fail to separate normally during meiosis or mitosis.

. The infant is at an increased risk for which disorder? A. Mental retardation B. Wilms tumor C. Triangular-shaped face D. Hypotonia

ANS: B Children with Beckwith-Wiedemann syndrome have an increased risk of developing Wilms tumor or hepatoblastoma. Mental retardation is associated with Angelman syndrome. A triangular-shaped face is associated with Russell-Silver syndrome. Hypotonia is associated with Prader-Willi syndrome.

This disease does not follow the inheritance patterns of single-gene disease. This type of disease is considered to be multifactorial. congenital. following a bell-shaped distribution model. following a liability of threshold model.

ANS: D Multifactorial diseases are caused by complex genetic and environmental factors. Congenital diseases are those present at birth. Most of these are multifactorial in etiology. Traits caused by the additive effects of many genetic and environmental factors, they tend to follow a normal or bell-shaped distribution in populations. Those diseases that do not follow the bell-shaped distribution appear to be either present or absent in individuals. They do not follow the inheritance patterns of single-gene disease. They follow a liability distribution that states that a threshold of liability must be crossed before the disease is expressed. Pyloric stenosis is an example of this type of disease.

In which two conditions are chromosomal abnormalities the leading known cause? Respiratory disorders Mental illness Intellectual disability Fetal miscarriage Cardiovascular disease

Chromosome abnormalities are the leading known cause of intellectual disability and fetal miscarriage.

Which genetic disorder is characterized by the presence of a zygote having one chromosome with a normal complement of genes and one chromosome with a missing gene? Cri du chat syndrome Klinefelter syndrome Down syndrome Turner syndrome

Cri du chat syndrome (translated as "cry of the cat") is caused by a DNA deletion. This term describes the cry often heard from a baby affected by the syndrome. Cri du chat syndrome can present as a microcephalic, low birth-weight baby with a piercing cry.

What are the empirical risks for most multifactorial diseases based on? Direct observation Chromosomal testing Liability thresholds Relative risks

Many factors from lifestyle to genetics affect multifactorial diseases. Observation and evaluation of each case individually provides the most thorough and accurate assessment.

Which type of risk is referred to as the ratio of the disease rate among the entire population to the disease rate in an unexposed population? Relative Contingency Causal Attributable

Relative risk is a ratio of probability, not an actual occurrence of disease.

How can an X-linked recessive disease skip generations? These diseases need only one copy of the gene in females. Females are hemizygous for the X chromosome. Mothers cannot pass X-linked genes to their sons. The disease can be transmitted through female carriers.

Since females have two copies of the X chromosome, the mother may provide an unaffected X to a daughter or son. Furthermore, a daughter may not show signs of the disease because she has the other X (the only X the father can give to a female) to cancel it out.

__________ refers to the silenced gene of a gene pair.

The imprinted gene is the silent gene of a gene pair.