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CHAPTER 2: The Cellular and Molecular Basis of Inheritance

1 Base substitutions:

a May result in nonsense mutations

b Can affect splicing

c Are always pathogenic

d Can affect gene expression

e Result in frameshift mutations

2 Transcription:

a Describes the production of polypeptides from the mRNA template

b Occurs in the nucleus

c Produces single-stranded mRNA using the antisense DNA strand as a template

d Is regulated by transcription factors that bind to the 3′ UTR

e Precedes 5′ capping and polyadenylation

3 The following are directly involved in DNA repair:

4 During DNA replication:

a DNA helicase separates the double-stranded DNA

b DNA is synthesized in one direction

c Okazaki fragments are synthesized

d DNA is synthesized in a conservative manner

e Uracil is inserted to pair with adenine

CHAPTER 3: Chromosomes and Cell Division

1 Meiosis differs from mitosis in the following ways:

a Daughter cells are haploid, not diploid

b Meiosis is restricted to the gametes and mitosis occurs only in somatic cells

c In mitosis, there is only one division

d Meiosis generates genetic diversity

e The prophase stage of mitosis is one step; in meiosis I, there are four stages

2 Chromosome abnormalities reliably detected by light microscopy include:

a Trisomy

b Monosomy

c Reciprocal translocation

d Interstitial deletion

e Robertsonian translocation

3 Fluorescent in situ hybridization using whole-chromosome (painting) or specific locus probes enables routine detection of:

a Gene amplification

b Subtelomeric deletion

c Trisomy

d Supernumerary marker chromosomes

e Reciprocal translocation

4 Chemicals used in the preparation of metaphase chromosomes for analysis by light microscopy include:

CHAPTER 4: DNA Technology and Applications

1 The following statements apply to restriction enzymes:

a They can generate DNA fragments with ‘sticky’ ends

b They are viral in origin

c They are used to detect point mutations

d They are used in Southern blotting

e They are also called restriction exonucleases

2 The following describe the polymerase chain reaction (PCR):

a A type of cell-free cloning

b A process that uses a heat-labile DNA polymerase

c A very sensitive method of amplifying DNA that can be prone to contamination

d A technique that can routinely amplify up to 100 kb of DNA

e A method of amplifying genes that requires no prior sequence knowledge

3 Types of nucleic acid hybridization include:

4 The following techniques can be used to screen genes for unknown mutations:

a Sequencing

b Single-stranded conformational polymorphism (SSCP)

c Denaturing high-performance liquid chromatography (DHPLC)

d Oligonucleotide ligation assay (OLA)

e Real-time PCR

CHAPTER 5: Mapping and Identifying Genes for Monogenic Disorders

1 Positional cloning uses:

a Genetic databases

b Knowledge of orthologous genes

c Patients with chromosomal abnormalities

d Candidate genes selected by biological knowledge

e Microsatellite markers

2 A candidate gene is likely to be a disease-associated gene if:

a A loss-of-function mutation causes the phenotype

b An animal model with a mutation in the orthologous gene has the same phenotype

c Multiple different mutations cause the phenotype

d The pattern of expression of the gene is consistent with the phenotype

e It is a pseudogene

3 Achievements of the Human Genome Project include:

a Draft sequence published in 2000

b Sequencing completed in 2003

c Development of bioinformatics tools

d Identification of all disease-causing genes

e Studies of ethical, legal, and social issues

CHAPTER 6: Developmental Genetics

1 In development, HOX genes:

a Function as transcription factors

b When mutated have been shown to be associated with many malformation syndromes

c Show very divergent structures across different species

d Are functionally redundant in postnatal life

e Individually can be important in the normal development of widely different body systems

2 In the embryo and fetus:

a Gastrulation is the process leading to the formation of the 16-cell early embryo 3 days after fertilization

b Organogenesis takes place at between 8 and 12 weeks’ gestation

c The notch signaling and sonic hedgehog pathways are important for ensuring normal development in diverse organs and tissues

d Somites form in a caudo-rostral direction from the presomitic mesoderm

e TBX genes appear to be crucial to normal limb development

3 Concerning developmental pathways and processes:

a In mammalian development, the jaw is formed from the second pharyngeal arch

b Pharyngeal arch arteries ultimately become the great vessels around the heart

c TBX1 is a key gene in the defects associated with DiGeorge syndrome

d Achondroplasia can be caused by a wide variety of mutations in the FGFR3 gene

e Loss-of-function mutations and gain-of-function mutations usually cause similar defects

4 Regarding the X-chromosome:

a In most males with a karyotype of 46,XX, the SRY gene is present and found on one of the X chromosomes

b In lyonization, or X-chromosome inactivation, all the genes of one X chromosome are switched off

c As a result of lyonization, all females are X-chromosome mosaics

d Male fetal development is solely dependent on the SRY gene having normal functioning

e X-chromosome inactivation may be linked in some way to the monozygotic twinning process

5 Transcription factors:

a Are RNA sequences that interfere with translation in the ribosomes

b Their only function is to switch off genes in development

c When mutated in Drosophila body segments may be completely reorganized

d Are not involved in defects of laterality

e Include genes that have a zinc finger motif

CHAPTER 7: Patterns of Inheritance

1 Concerning autosomal recessive inheritance:

a Females are more likely to be affected than males

b If both parents are carriers, the risk at conception that any child might be a carrier is

c Diseases following this pattern of inheritance are more common in societies where cousin marriage is normal

d Usually only a single generation has affected individuals

e Angelman syndrome follows this pattern

2 Concerning X-linked inheritance:

a The condition cannot be passed from an affected father to his son

b When recessive, an affected man will not see the condition in his children but it may appear in his grandchildren

c When dominant, females are usually as severely affected as males

d When dominant, there are usually more affected females than affected males in a family

e The risk of germline mosaicism does not need to be considered

3 In mitochondrial genetics:

a Heteroplasmy refers to the presence of more than one mutation in mitochondria

b Mitochondrial genes mutate less often than nuclear genes

c Mitochondrial conditions affect only muscle and nerve tissue

d The risk of passing on a mitochondrial condition to the next generation may be as high as 100%

e Mitochondrial diseases have nothing to do with nuclear genes

4 Concerning terminology:

a Locus heterogeneity means that the same disease can be caused by genes on different chromosomes

b Pseudo-dominance refers to the risk to the offspring when both parents have the same dominantly inherited condition

c If a condition demonstrates reduced penetrance it may skip generations

d Variable expression characterizes diseases that demonstrate anticipation

e Pleiotropy is simply a more striking form of variable expression

5 In inheritance:

a An autosomal recessive condition can occasionally arise through uniparental disomy

b Imprinted genes can be unmasked through uniparental disomy

c Digenic inheritance is simply another way of referring to uniparental disomy

d Hormonal factors may account for conditions demonstrating sex influence

e Most of the human genome is subject to imprinting

CHAPTER 8: Mathematical and Population Genetics

1 In applying the Hardy-Weinberg equilibrium, the following assumptions are made:

a The population is small

b There is no consanguinity

c New mutations do not occur

d No babies are born by donor insemination

e There is no significant movement of population

2 If the population incidence of a recessive disease is 1 in 10,000, the carrier frequency in the population is:

3 Heterozygote advantage:

a May lead to an increased incidence of autosomal dominant disorders

b Does not mean that biological fitness is increased in the homozygous state

c May explain the worldwide distribution of sickle cell disease and malaria

d May lead to distortion of the Hardy-Weinberg equilibrium

e Is very unlikely to be traced to a founder effect

4 Polymorphic loci:

a Are defined as those loci at which there are at least two alleles, each with frequencies greater than 10%

b Have been crucial to gene discoveries

c Can be helpful in determining someone’s genetic status in a family

d Have nothing to do with calculating LOD scores

e By themselves have no consequence for genetically determined disease

5 In population genetics:

a To calculate the mutation rate for a disorder, it is necessary only to know the biological fitness for the condition

b If medical treatment can improve biological fitness, the frequency of an autosomal dominant condition will increase far more rapidly than that of an autosomal recessive condition

c Even when a large number of families is studied, the calculated segregation ratio for a disorder might not yield the expected figures for a given pattern of inheritance

d For X-linked disorders, the frequency of affected males equals the frequency of the mutated allele

e Autozygosity mapping is a useful strategy to look for the gene in any autosomal recessive condition

CHAPTER 9: Polygenic and Multifactorial Inheritance

1 Concerning autism:

a It is best classified as an inborn error of metabolism

b The concordance rate in dizygotic twins is approximately 50%

c Fragile X syndrome is a major cause

d The risk to the siblings of an affected person is approximately 5%

e Girls are more frequently affected than boys

2 Linkage analysis is more difficult in multifactorial conditions than in single-gene disorders because:

a Variants in more than one gene are likely to contribute to the disorder

b The number of affected persons within in a family is likely to be fewer than for a single-gene disorder

c The mode of inheritance is usually uncertain

d Some multifactorial disorders are likely to have more than one etiology

e Many multifactorial conditions have a late age of onset

3 Association studies:

a Can give false-positive results because of population stratification

b Include the transmission disequilibrium test (TDT)

c Positive association studies should be replicated

d Are used to map genes in multifactorial disorders

e Require closely matched control and patient groups

4 Variants in genes that confer susceptibility to type 2 diabetes (T2DM) have been found:

a By linkage analysis using affected sibling pairs

b Using animal models

c By candidate gene studies from monogenic subtypes of diabetes

d Through the study of biological candidates

e In isolated populations

5 Variants in the NOD2/CARD15 gene:

a Are associated with Crohn disease and ulcerative colitis

b Can result in a 40-fold increased risk of disease

c Were identified after the gene was mapped to chromosome 16p12 by positional cloning

d Has led to novel therapies

e Are very rare in the general population

CHAPTER 10: Hemoglobin and the Hemoglobinopathies

1 For different hemoglobins:

a The fetal hemoglobin chain, γ, resembles the adult β chain

b The Hb chains, α, β and γ are all expressed throughout fetal life

c In α-thalassemia, there are too many α chains

d Hb Barts is a form of β-thalassemia

e Carriers of β-thalassemia frequently suffer from symptomatic anemia

2 Regarding sickle cell disease:

a The sickling effect of red blood corpuscles is the result of abnormal Hb binding with the red blood cell membrane

b Life-threatening thrombosis can occur

c Hb S differs from normal Hb A by a single amino-acid substitution

d Splenic infarction may occur but this has little clinical consequence

e Point (missense) mutations are the usual cause of abnormal Hb in the sickling disorders

3 Concerning hemoglobin variants:

a Many Hb variants are harmless

b The types of mutation occurring in the hemoglobinopathies are very limited

c In the thalassemias, hypoplasia of the bone marrow occurs

d In the thalassemias, Hb demonstrates abnormal oxygen affinity

e In some thalassemias, increased red cell hemolysis occurs

4 Regarding hemoglobins during life:

a Persistence of fetal Hb into adult life is an acquired disorder

b Throughout fetal life, it is the liver that produces most of the body’s Hb

c The bone marrow is not involved in Hb production before birth

d The liver continues to produce Hb into the second year of postnatal life

e Persistence of fetal Hb into adult life is a benign condition

CHAPTER 11: Biochemical Genetics

1 In congenital adrenal hyperplasia (CAH):

a Females may show virilization and ambiguous genitalia

b Males may show undermasculinization and ambiguous genitalia

c Mineralocorticoid deficiency can be life threatening

d Treatment is required during childhood but not usually in adult life

e In affected females, fertility is basically unaffected

2 Phenylketonuria:

a Is the only cause of a raised phenylalanine level in the neonatal period

b Requires lifelong treatment

c Is a cause of epilepsy and eczema

d Results in reduced levels of melanin

e Is part of the same pathway as cholesterol production

3 Hepatomegaly is an important feature of:

a Hurler syndrome

b Glycogen storage disorders

c Abnormalities of porphyrin metabolism

d Niemann-Pick disease

e Galactosemia

4 Concerning mitochondrial disorders:

a All follow matrilinear inheritance

b Retinal pigmentation and diabetes can both be features

c There are fewer than 50 gene products from the mitochondrial genome

d Leigh disease is always caused by the same point mutation

e The gene for Barth syndrome is known but the metabolic pathway is uncertain

5 Regarding metabolic conditions:

a The carnitine cycle and long-chain fatty acids are linked

b A single point mutation explains most cases of MCAD (medium-chain acyl-CoA dehydrogenase) deficiency

c Peroxisomal disorders include Menkes disease and Wilson disease

d Inborn errors of metabolism may present with hypotonia and acidosis alone

e X-rays are of no value in making a diagnosis of inborn errors of metabolism

CHAPTER 12: Pharmacogenetics

1 Thiopurine drugs used to treat leukemia:

a Include 6-mercaptopurine, 6-thioguanine, and azathioprine

b Are also used to suppress the immune system

c May be toxic in 1–2% of patients

d Can have serious side-effects

e Are metabolized by thiopurine methyltransferase (TPMT)

2 Liver enzymes that show genetic variation of expression and hence influence the response to drugs include:

a UDP-glucuronosyltransferase

b O-acetyltransferase

c Alcohol dehydrogenase

d CYP2D6

e CYP2C9

3 The following have an increased risk of complications from anesthesia:

a First-degree relatives of patients affected with malignant hyperthermia

b Patients with RYR1 mutations

c Patients with G6DP deficiency

d Patients with CHE1 mutations

e Patients with raised pseudocholinesterase levels

4 Examples of diseases in which treatment may be influenced by pharmacogenetics include:

a Maturity-onset diabetes of the young (MODY), subtype glucokinase

b Maturity-onset diabetes of the young (MODY), subtype HNF-1α

c HIV infection

d Epilepsy

e Tuberculosis

CHAPTER 13: Immunogenetics

1 Concerning complement:

a The complement cascade can be activated only by the binding of antibody and antigen

b C1-inhibitor deficiency can result in complement activation through the classic pathway

c C3 levels are reduced in hereditary angioneurotic edema

d Complement helps directly in the attack on microorganisms

e Complement is found mainly in the intracellular matrix

a The immunoglobulin molecule is made up of six polypeptide chains

b The genes for the various light and heavy immunoglobulin chains are found close together in the human genome

c Close relatives make the best organ donors because they are likely to share the same complement haplotypes

d The DNA encoding the κ light chain contains four distinct regions

e The diversity of T-cell surface antigen receptor can be compared with the process of immunoglobulin diversity

a Maternal transplacental mobility of antibodies gives infants protection for about 12 months

b X-linked severe combined immunodeficiency (SCID) accounts for about 5–10% of the total of SCID

c SCID, despite its name, is not always a severe condition

d There is always a T-cell abnormality in the different forms of SCID

e Chronic granulomatous disease (CGD) is a disorder of humoral immunity

a DiGeorge/Sedláčková syndrome is a primary disorder of immune function

b Severe opportunistic bacterial infections are uncommon in DiGeorge syndrome

c Genetic prenatal diagnosis is possible for common variable immunodeficiency (CVID)

d Autoimmune disorders follow autosomal dominant inheritance

e Investigation of immune function should be considered in any child with failure to thrive (FTT)

CHAPTER 14: Cancer Genetics

a Chromosome translocations can lead to cancer through modification of oncogene activity

b Oncogenes are the most common forms of genes predisposing to hereditary cancer syndromes

c Defective apoptosis may lead to tumorigenesis

d Loss of heterozygosity (LOH) is another term for a mutational event in an oncogene

e A mutation in the APC gene is sufficient to cause colorectal cancer

a The two-hit hypothesis predicted that a tumor would develop when both copies of a critical gene were mutated

b TP53 mutations are found only in Li-Fraumeni syndrome

c The RET proto-oncogene is implicated in all forms of multiple endocrine neoplasia (MEN)

d Individuals with familial adenomatous polyposis (FAP) should have screening of the upper gastrointestinal tract

e Endometrial cancer is a feature of hereditary non-polyposis colon cancer (HNPCC)

a Thyroid cancer is a risk in Bannayan-Riley-Ruvalcaba syndrome

b Men with a germline mutation in BRCA2 are at increased risk of prostate cancer

c The genetic basis of all familial breast cancer is now well established

d Familial breast cancer is usually fully penetrant

e For men with prostate cancer, 3% of male first-degree relatives are similarly affected

a Medulloblastoma is a common tumor in von Hippel-Lindau (VHL) disease

b Pheochromocytoma is frequently seen in Gorlin syndrome

c There is a risk of ovarian cancer in Peutz-Jegher syndrome and HNPCC

d Cutaneous manifestations occur in Peutz-Jegher syndrome, Gorlin syndrome, and HNPCC

e In two-thirds of HNPCC cases the predisposing gene is unknown

a Screening for renal cancer in VHL is recommended

b Mammography detects breast cancer more easily in premenopausal than postmenopausal women

c Screening for retinoblastoma should begin in the second year of life

d Colorectal cancer in two close relatives is sufficient to indicate the need for colonoscopy screening in other family members

e Preventive surgery is strongly indicated in FAP and women positive for BRCA1 mutations

CHAPTER 15: Genetic Factors in Common Diseases

a A genetic factor is thought to be present in 10% of epilepsy

b Mutations in potassium channel genes predispose to epilepsy

c Juvenile myoclonic epilepsy follows autosomal dominant inheritance

d Epilepsy is common in deletion 1p36 syndrome

e Unverricht-Lundborg disease is a benign form of mendelian epilepsy

a There is a high risk of bipolar depressive illness in DiGeorge syndrome

b The concordance rate for schizophrenia in monozygotic twins is approximately 80%

c No mutations have so far been found in any gene to provide a cause for schizophrenia

d Twin studies suggest a similar heritability for bipolar and unipolar illness

e Analysis of APOE ε4 is recommended as a screening procedure for Alzheimer disease

a Susceptibility for Creutzfeldt-Jakob disease is conferred by homozygosity for a prion protein (PRNP) polymorphism

b So far, three genes are known to cause autosomal dominant Alzheimer disease

c Presenilin-1 is a low-penetrance gene for early-onset Alzheimer disease

d Linkage studies are more important than twin studies in understanding the genetic contribution to bipolar illness

e Persons with Down syndrome are at significant risk of Alzheimer disease

4 Hemochromatosis:

a Is genetically heterogeneous

b Affects more women than men

c Can be treated by phlebotomy

d Is fully penetrant

e Is usually caused by a homozygous H63D mutation in the HFE gene

5 The following statements about venous thrombosis are true:

a Factor V Leiden and the prothrombin G20210A variant are common causes of venous thrombosis

b Testing for factor V Leiden and the prothrombin variant will change the management of a patient with venous thrombosis

c The factor V Leiden mutation causes reduced expression of the factor V gene

d The prothrombin variant causes increased expression of the prothrombin gene

e Compound heterozygotes for factor V Leiden and the prothrombin variant have a 20-fold increased risk of venous thrombosis

CHAPTER 16: Congenital Abnormalities and Dysmorphic Syndromes

a Around 5% of all infant deaths are due to congenital abnormalities

b At least half of all spontaneous miscarriages have a genetic basis

c A major congenital abnormality affects approximately one newborn baby in every 100

d Positional talipes is an example of a disruption to normal intrauterine development

e Multiple abnormalities are sometimes the result of a sequence

a Down syndrome should more accurately be termed ‘Down association’

b Sotos syndrome, as with Down syndrome, is due to a chromosomal abnormality

c Spina bifida affects approximately 2 per 1000 births

d Infantile polycystic kidney disease is an example of a condition with different patterns of inheritance

e Holoprosencephaly is an example of a condition with different patterns of inheritance

a Thalidomide embryopathy was an example of a disruption to normal intrauterine development

b Talipes may be a consequence of renal agenesis

c Limb defects are not caused by fetal exposure to sodium valproate

d Symmetrical defects tend to feature in a dysplasia

e Birth defects are unexplained in 20% of cases

a Congenital infection could lead to someone being both blind and deaf

b The mid-trimester is the most dangerous time for a fetus to be exposed to a maternal infection

c Vertebral body defects can be a consequence of poorly treated diabetes mellitus in the first trimester

d A polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene is always associated with an increased risk of neural tube defect

e Pulmonary stenosis is a feature of Noonan syndrome and congenital rubella

a Cleft lip–palate occurs more frequently than 1 in 1000 births

b Associations generally have a high recurrence risk

c The recurrence risk for a multifactorial condition can usually be determined by looking at patient’s family pedigree

d One cause of holoprosencephaly is a metabolic defect

e Congenital heart disease affects 1 in 1000 babies

CHAPTER 17: Genetic Counseling

a The individual who seeks genetic counseling is the proband

b Retinitis pigmentosa is not genetically heterogeneous

c Genetic counseling is all about recurrence risks

d The counselor’s own opinion about a difficult choice is always helpful

e Good counseling should not be measured by the patient’s/client’s ability to remember genetic risks

a First-cousin partnerships are 10 times more likely to have babies with congenital abnormalities than the general population

b On average, a grandparent and grandchild share

of their genes

c Incestuous relationships virtually always result in severe learning difficulties in the offspring

d Consanguinity should be regarded as extremely abnormal

e Consanguinity refers exclusively to cousin marriages/partnerships

a Genetic disorders are accidents of nature, so guilt feelings are rare

b Clear genetic counseling changes patients’ reproductive decisions in virtually all cases

c The chance of first cousins having their first child affected with an autosomal recessive condition due to a deleterious gene inherited from a grandparent is 1 in 32

d Far more genetic testing of children for adoption takes place than for children reared by their birth parents

e Patient support groups have little value given that modern medical genetics is so technically complex

CHAPTER 18: Chromosome Disorders

a The chromosome number in humans was discovered after the structure of DNA

b The Turner syndrome karyotype is the most common single chromosome abnormality in spontaneous abortuses

c The rate of miscarriage in Down syndrome is similar to the rate in karyotypically normal fetuses

d Most babies with Down syndrome are born to mothers age younger than 30 years

e All children with Down syndrome have to go to special school

a The life expectancy of children with trisomy 18 (Edwards syndrome) is about 2 years

b 47,XYY males are fertile

c The origin of Turner syndrome (45,X) can be in paternal meiosis

d All persons with Angelman syndrome have a cytogenetically visible deletion on chromosome 15q

e DiGeorge syndrome results from misaligned homologous recombination between flanking repeat gene clusters

a Premature vascular problems occur in adults with Williams syndrome

b Congenital heart disease is a feature of Prader-Willi and Smith-Magenis syndromes

c The Wilms tumor locus is on chromosome 13

d Aniridia may be caused by either a gene mutation or a chromosome microdeletion

e A child’s behavior may help to make a diagnosis of a malformation syndrome

a Klinefelter syndrome affects approximately 1 in 10,000 male live births

b Learning difficulties are common in Klinefelter syndrome

c Chromosome mosaicism is commonly seen in Turner syndrome

d Females with a karyotype 47,XXX are infertile

e Chromosome breakage syndromes can cause cancer

a In fragile X syndrome, the triplet repeat does not change in size significantly when passed from father to daughter

b Fragile X syndrome is a single, well-defined, condition

c Girls with bilateral inguinal herniae should have their chromosomes tested

d Normal karyotyping is a good way of diagnosing fragile X syndrome in girls

e FISH analysis using multi-telomeric probes diagnoses about 25% of non-specific learning difficulties

CHAPTER 19: Single-Gene Disorders

a In Huntington disease (HD), an earlier age of onset in the offspring is more likely if the gene is passed from an affected mother rather than an affected father

b In HD, those homozygous for the mutation are no more severely affected than those who are heterozygous

c From the onset of HD, the average duration of the illness until a terminal event is 25–30 years

d In HD, non-penetrance of the disease may be associated with low repeat abnormal alleles

e Anticipation is a feature of the inheritance of myotonic dystrophy

a Insomnia is a feature of myotonic dystrophy

b Myotonic dystrophy is a cause of neonatal hypertonia

c The clinical effects of myotonic dystrophy are mediated through RNA

d Cardiac conduction defects are a feature of myotonic dystrophy and ion channelopathies

e The diagnosis of cystic fibrosis (CF) may come to light only in the infertility clinic

a In CF the R117H mutation is the most common one in northern Europe

b In the CFTR gene a modifying intragenic polymorphism affects the phenotype

c Hypertrophic cardiomyopathies are mostly due to mutations in ion channelopathy genes

d Many different inherited muscular dystrophies can be linked to the complex that includes dystrophin (mutated in Duchenne and Becker muscular dystrophies)

e Learning difficulties are part of spinal muscular atrophy

a Cystic fibrosis and hemophilia are unlikely candidates for gene therapy

b An abnormal span : height ratio alone is a major feature of Marfan syndrome

c Neurofibromatosis type 1 (NF1) sometimes ‘skips generations’

d Scoliosis can be a feature of both NF1 and Marfan syndrome

e Cataracts can be a feature of NF1 but not of NF2

a HMSN types I and II refer to a genetic classification

b HMSN can follow all major patterns of inheritance

c It is the nerve sheath, rather than the nerve itself, that is altered in the most common form of HMSN

d Estimation of the creatine kinase level and factor VIII level is good for identifying carriers of Duchenne dystrophy and hemophilia, respectively

e Brugada syndrome is one of the varieties of spinal muscular atrophy

CHAPTER 20: Screening for Genetic Disease

a X-inactivation studies provide a useful means of identifying female carriers of some X-linked disorders

b Reliable clinical signs to detect most carriers of X-linked disorders are lacking

c DNA sequence variants are useful in targeted screening as long as they are not polymorphic

d DNA markers are useful in targeted screening for retinitis pigmentosa

e For the purposes of screening family members, opportunities should be taken for the banking of DNA from probands with lethal conditions

a Patients with presymptomatic tuberous sclerosis always have a characteristic facial rash

b It is always possible to diagnose neurofibromatosis type 1 by age 2 years because it is a fully penetrant condition

c Biochemical tests should not be considered as diagnostic genetic tests

d Magnetic resonance imaging of the lumbar spine may be useful in diagnosing Marfan syndrome

e Predictive genetic testing must always be done by direct gene analysis

a Population screening programs should be legally enforced

b Population screening programs should be offered if some form of treatment or prevention is available

c The sensitivity of a test refers to the extent to which the test detects only affected individuals

d The positive predictive value of a screening test refers to the proportion of positive tests that are true positives

e If there is no effective treatment for a late-onset condition, predictive genetic testing should be undertaken with great care

a A high proportion of people who undergo carrier testing cannot remember their result properly

b Carrier screening for cystic fibrosis is the most useful program among Greek Cypriots

c The possibility of a screening test leading to employment discrimination is not a major concern

d Neonatal screening for Duchenne muscular dystrophy improves life expectancy

e Neonatal screening for cystic fibrosis is a DNA-based test

a Newborn screening for hemochromatosis, the most common mutated gene in European populations, is a nationally managed program in the United Kingdom

b The presymptomatic screening of children for adult-onset genetic disease is a decision made by the parents

c Neonatal screening for phenylketonuria and congenital hypothyroidism are the longest-running screening programs

d Screening for MCAD (medium-chain acyl-CoA dehydrogenase) deficiency is integrated into neonatal population screening

e Genetic registers are mainly for research

CHAPTER 21: Prenatal Testing and Reproductive Genetics

1 In prenatal testing:

a Amniocentesis is being routinely practiced earlier and earlier in pregnancy

b The cells grown from amniocentesis originate purely from fetal skin

c The risk of miscarriage is higher from chorionic villus sampling (CVS) than from amniocentesis

d CVS is a safe procedure at 9 weeks’ gestation

e Fetal skin disorders can be diagnosed by ultrasonography

2 Regarding prenatal markers:

a In Down syndrome pregnancies, maternal serum human chorionic gonadotropin (hCG) levels are usually raised

b In Down syndrome pregnancies, maternal serum α-fetoprotein (αFP) concentration is usually reduced

c In trisomy 18 pregnancies, maternal serum markers behave in just the same way as in Down syndrome pregnancies

d About 95% of Down syndrome pregnancies are picked up by determining maternal age, serum αFP and hCG levels, and fetal nuchal translucency

e Twin pregnancy is a cause of increased maternal serum αFP levels

a Chromosome mosaicism is detected in about 5% of CVS samples

b Chromosome disorders are the main cause of abnormal nuchal translucency

c Echogenic fetal bowel on ultrasonography is a risk factor for cystic fibrosis

d For a couple who have had one child with Down syndrome, the risk in the next pregnancy is usually not greatly increased

e Familial marker chromosomes are usually not clinically significant

a Donor insemination is a procedure not requiring a license from the HFEA

b Surrogacy is illegal in the United Kingdom

c For preimplantation genetic diagnosis (PGD), fertilization of the egg is achieved by intracytoplasmic sperm injection (ICSI)

d The success rate from IVF, in terms of taking home a baby, is only about 50%

e The largest group of diseases being tested in PGD is single-gene conditions

a There is an increased risk of genetic conditions in the children conceived by ICSI

b The sperm of one donor may be used only five times

c Children conceived by donor insemination are entitled to as much information as adopted children about their biological parents

d If prenatal diagnosis could be achieved by analyzing fetal cells in the maternal circulation, the couple would still have to consider termination of pregnancy

e Infertility affects about 1 in 20 couples

CHAPTER 22: Risk Calculation

a A probability of 0.5 is the same as a 50% risk

b The probability of an event never exceeds unity

c In a dizygotic twin pregnancy, the probability that the babies will be the same sex equals 0.5

d Bayes’ theorem takes account of both prior probability and conditional information

e In an autosomal dominant condition, a penetrance of 0.7 means that 30% of heterozygotes will not manifest the disorder

2 For an autosomal recessive condition, the chance that the first cousin of an affected individual is a carrier is:

3 In X-linked recessive inheritance:

a The sons of a female carrier have a 1 in 4 chance of being affected

b The mother of an affected male is an obligate carrier

c The gonadal mosaicism risk in Duchenne muscular dystrophy may be as high as 10%

d For a woman who has an affected son, her chance of being a carrier is reduced if she goes on to have three unaffected sons

e A dummy consultand refers to an individual in a pedigree who is ignored when it comes to calculating risk

4 In autosomal recessive inheritance, the risk that the nephew of an affected individual, born to the affected individual’s healthy sibling, is a carrier is:

a In calculating risk, conditional information can include negative DNA data

b In delayed onset of a dominantly inherited condition, calculation of heterozygote risk requires clinical expression data

c Calculating odds ratios does not require information about prior probabilities

d Empiric risks derived from epidemiological studies have limited application to a particular situation

e When using DNA marker data to predict risk, the recombination fraction does not really matter

CHAPTER 23: Treatment of Genetic Disease

1 Methods currently used to treat genetic disease include:

a Germ-cell gene therapy

b Stem-cell transplantation

c Enzyme/protein replacement

d Dietary restriction

e In situ repair of mutations by cellular DNA repair mechanism

2 Gene therapy may be delivered by:

a Liposomes

b Adeno-associated viruses

c Antisense oligonucleotides

d Lentiviruses

e Injection of plasmid DNA

3 Gene therapy has been used successfully to treat patients with the following diseases:

a Cystic fibrosis

b Severe combined immunodeficiency (XL-SCID)

c Sickle cell disease

d Hemophilia

e Adenosine deaminase deficiency

4 Potential gene therapy methods for cancer include:

a Inhibition of fusion proteins

b Stimulation of the immune system

c Increased expression of the angiogenic factors

d RNA interference

e Antisense oligonucleotides

Emerys Elements of Medical Genetics

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