Chapter 4: Genes and Genetic Diseases MULTIPLE CHOICE
1. Inserting bone marrow cells into an individual who produ ces abnormal erythrocytes is an
example of what type of therapy? a. Somatic cell b. Germ cell
c. Genetic engineering d. Recombinant D!
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Gene therapy can be applied in two ways. #he less controversial approach is somatic cell therapy$ which consists of inserting inserting normal genes into the cells of an individual who has a genetic disease. In this approach$ a particular tissue$ such as bone marrow cells that produce abnormal erythrocytes$ is treated. #he correct option is the only on e that accurately identifies the therapy described in the %uestion. &#S" 1
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/. D! replication re%uires the en0yme D! polymerase to" a. #ravel along the single D! strand$ adding the correct nucleotide to the new strand b. ove along the double strand of D! to unwind the nucleotides of the double
helix c. 2old the double strand apart while the correct nucleotides are added to the strand d. #ransport the double strand of D! from the nucleus to the cytoplasm for protein formation !S" !
#he D! polymerase en0yme travels along the single D! strand$ adding the correct nucleotides to the free end of the new strand 3see (igure -/$ B -/$ B4. 4. #he correct option is the only one that accurately describes the process involved in D! replication using D! polymerase. &#S" 1
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). #ranscription is best defined as a process by which" a. D! polymerase binds to the promoter site on ribonucleic acid 3R!4. b. R! directs the synthesis of polypeptides for protein synthesis. c. R! is synthesi0ed from a D! template. d. ! base pair substitution results in a mutation of the amino acid se%uence. !S" 5
#ranscription is the process by b y which R! is synthesi0ed from a D! template. #he correct option is the only one that accurately defines the term transcription. transcription. &#S" 1
R'(" &age 1-1
-. #he purpose of a staining techni%ue of chromosomes such as Giemsa is to" a. &ermit the mitotic process to be followed and monitored for v ariations. b. !llow for the numbering of chromosomes and the identification of variations. c. Identify new somatic cells formed through mitosis and cyto6inesis. d. Distinguish the sex chromosomes from the homologous chromosomes.
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7ne of the most commonly used stains is Giemsa stain. ,y using banding techni%ues$ chromosomes can be unambiguously numbered$ and individual variation in chromosome composition can be studied. issing or duplicated portions of chromosomes$ which often result in serious diseases$ also can be readily identified. #he correct option is the only one that accurately describes the purpose of the Giemsa staining techni%ue. &#S" 1
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8. !n amniocentesis indicates a neural tube defect when an increase in which protein is evident? a. 5horionic c. !mniotic b. !lpha fetoprotein d. 'mbryonic !S" ,
7ther disorders can be detected with this procedure. #hese include most neural tube defects$ which cause an elevation of o f alpha fetoprotein in the amniotic fluid$ and hundreds of diseases caused by mutations of single genes. #he correct co rrect option is the only one that accurately identifies the protein responsible for a neural tube defect. &#S" 1
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9. !n amniocentesis is recommended for pregnant women who" a. 2ave a history of chronic illness b. 2ave a family history of genetic disorders c. 2ave experienced in vitro fertili0ation d. 2ad a late menarche !S" ,
!mniocentesis is recommended only for pregnancies 6nown to have an elevated ris6 for a genetic disease or in women older than ): to )8 years of age. #he correct option is the only one that accurately describes a criterion for ordering an amniocentesis. &#S" 1
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*. #he most clinically useful techni%ue for prenatal diagnosis of chromosomal ab normalities at )
months; 31/ wee6s;4 gestation is" a. Gene mapping b.
c. !mniocentesis d. 5horionic villus sampling
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Chorionic villus sampling consists of extracting a small amount of villous tissue directly from the chorion. #his procedure can be performed at 1: wee6s; gestation gestation and does not re%uire in vitro culturing of cells= sufficient numbers are directly available in the extracted tissue. #hus the procedure allows prenatal diagnosis at approximately ) months; gestation gestation rather than at nearly 8 months; gestation. gestation. #he correct option is the only one that accurately describes the most useful techni%ue for prenatal diagnosis of chromosomal abnormalities. &#S" 1
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>. #he term for an error in which homologous chromosomes fail to separate during meiosis or
mitosis is" a. !neuploidy
c.
&olyploidy
b. ondisunction
d. #ranslocation
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!neuploidy is usually the result of nondisunction$ an error in which homologous chromosomes or sister chromatids fail to separate normally during meiosis or mitosis. #he correct option is the only one that is used to describe an error in chromosomal ch romosomal separation during reproduction. &#S" 1
R'(" &age 1-8
@. Ahich clinical manifestations would be expected for a child who has complete trisomy of the
twentyfirst chromosome? a. Aidely spaced nipples$ reduced carrying angle at the elbow$ and sparse body hair b. !n IB of /8 to *:$ low nasal bridge$ protruding tongue$ and flat$ lowset ears c. 2ighpitched voice$ tall stature$ gynecomastia$ and an IB of 9: to @: d. 5ircumoral cyanosis$ edema of the feet$ short stature$ and mental slowness !S" ,
Individuals with this disease are mentally retarded$ with IBs usually ranging from /8 to *:. #he facial appearance is distinctive and exhibits a low nasal bridge$ epicanthal folds 3which produce a superficially !sian !sian appearance4$ protruding tongue$ and flat$ lowset ears. #he correct option is the only one that accurately describes the clinical manifestations of the complete trisomy of the twentyfirst chromosome. &#S" 1
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1:. Ahat is the most common cause of Down syndrome? a. &aternal nondisunction c. aternal nondisunction b. aternal translocations d. &aternal translocation !S" 5
ondisunction during the formation of one of the parent;s gametes or during early embryonic development occurs in approximately @*C of infants born with Down syndrome. In approximately @:C to @8C of infants$ the nondisunction occurs in the formation of the mother;s egg cell. #he correct option is the only one that accurately describes the most common cause of Down syndrome. &#S" 1
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11. Ahat syndrome$ characteri0ed by an absent homologous chromosome with only a single
chromosome$ exhibits features that include a short stature$ widely spaced nipples$ and webbed nec6? a. Down c. #urner b. 5ri du chat d. Elinefelter !S" 5
In #urner syndrome$ a sex chromosome is missing$ and the person;s total total chromosome count is -8. 5haracteristic signs include short stature$ female genitalia$ webbed nec6$ shieldli6e chest with underdeveloped breasts and widely spaced nipples$ and imperfectly developed ovaries. #he correct option is the only one that accurately describes the clinical manifestations described in the %uestion.
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1/. ! person with -*$ F 6aryotype has the genetic disorder resulting in which syndrome? a. #urner c. Down b. Elinefelter d. (ragile !S" ,
! disorder in the chromosome 3-*$ F 6aryotype4 results in a disorder 6nown as Klinefelter as Klinefelter syndrome. syndrome. #he correct option is the only one that accurately describes a genetic disorder that exhibits the described genetic configuration. &#S" 1
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1). Ahat is the chromosomal variation that causes Elinefelter syndrome? a. ondisunction of the chromosome in the father b. #ranslocation of the chromosome in the mother c. ondisunction of chromosome in the mother d. #ranslocation of the F chromosome in the father !S" 5
ondisunction of the chromosomes in the mother causes Elinefelter syndrome syndrome in the maority of infants$ and the fre%uency of the disorder rises with maternal age. #he correct option is the only one that accurately describes the chromosomal variation characteristic of Elinefelter syndrome. &#S" 1
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1-. Ahat is the second most commonly recogni0ed genetic cause of mental retardation? a. Down syndrome c. Elinefelter syndrome b. (ragile syndrome d. #urner syndrome !S" ,
#he fragile syndrome is the second most common genetic cause of mental retardation 3after Down syndrome4. #he correct option is not observed with enough fre%uency to be recogni0ed as the second most common cause of mental retardation. &#S" 1
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18. Ahat is the blood type of a person who is hetero0ygous$ having ! and , alleles as
codominant? a. ! b. ,
c. 7 d. !,
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Ahen the hetero0ygote is distinguishable from both homo0 ygotes$ the locus is said to exhibit codominance. !n example is the !,7 blood group$ in which hetero0ygotes having the A the A and B alleles express both of them as ! and , antigens on their red cells 3forming blood group !,4. #he correct option is the only one that accurately describes codominance. &#S" 1
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19. ! couple has two children diagnosed with an autosomal dominant gen etic disease. Ahat is the
probability that the next child will have the same genetic disease? a. 7ne sixth c. 7ne third b. 7ne fourth d. 7ne half !S" D
!ffected hetero0ygous individuals transmit the trait to approximately one half of their children= however$ because gamete transmission is subect to chance fluctuations$ it is possible that all or none of the children of an affected parent may have the trait. evertheless$ when large numbers of matings of this type are studied$ the propo rtion of affected children closely approach one half. &#S" 1
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1*. Ahen a child inherits a disease that is autosomal recessive$ it is inherited from" a. (ather c. ,oth parents b. other d. Grandparent !S" 5
In most cases of recessive disease$ both parents of affected individuals are hetero0ygous carriers. &#S" 1
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1>. &eople diagnosed with neurofibromatosis have varying degrees of the condition because of
the genetic principle of" a. &enetrance b. 'xpressivity
c. Dominance d. Recessiveness
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Expressivity is the extent of variation in phenotype associated with a particular a particular genotype. If expressivity of a disease is variable$ then the penetrance the penetrance may be complete but the severity of the disease can vary greatly. ! well6nown example of variable expressivity in an autosomal dominant disease is type 1 neurofibromatosis. #he correct option is the only one that accurately describes the presence of varying de grees of symptomatologic characteristics. &#S" 1
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1@. Ahich genetic disease has been lin6ed to a mutation of the tumorsuppressor gene? a. 2emochromatosis c. (amilial breast cancer b. Retinoblastoma d. 2emophilia ! !S" ,
#he gene responsible for retinoblastoma has been mapped to the long arm of chromosome 1)$ and its D! se%uence has been extensively studied. #his gene is 6nown as a tu!r" suppress!r #ene$ the normal function of its protein product is to regulate the cell cycle so that cells do not grow uncontrollably. #he correct option is the only one that accu rately identifies a disease resulting from a mutation of the tumorsuppressor gene. &#S" 1
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/:. 5ystic fibrosis is caused by what type of gene?
a. lin6ed dominant b. lin6ed recessive
c. !utosomal dominant d. !utosomal recessive
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#he most common lethal autosomal recessive disease in white children$ cystic fibrosis$ occurs in approximately 1 in /8:: births. #he correct option is the only one that accurately identifies the gene type responsible for cystic fibrosis. &#S" 1
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/1. Ahich is an important criterion for discerning autosomal recessive inheritance? a. 5onsanguinity is sometimes present. b. (emales are affected more than males. c. #he disease is observed in both the parents$ as well as in the siblings. d. 7n average$ one half of the offspring of the carrier will be affected. !S" !
5onsanguinity is often an important characteristic of pedigrees for recessive diseases= relatives share a certain proportion of genes received from a common ancestor. #he correct option is the only one that accurately identifies a re%uired factor in autosomal recessive genetic inheritance. &#S" 1
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//. 5onsanguinity refers to the mating of persons" a. Aho are unrelated b. Ahen one has an autosomal dominant disorder c. 2aving common family relations d. Ahen one has a chromosomal abnormality !S" 5
Consanguinity refers to the mating of two related individuals$ and the offspring of such matings are said to be inbred. #he correct option is the only one that accurately identifies consanguinity as it relates to human mating. &#S" 1
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/). ales$ having only one chromosome 3as is expected4$ are said to be" a. 2omo0ygous c. 2emi0ygous b. 2etero0ygous d. !mbi0ygous !S" 5
ales$ having only one chromosome$ are said to be hemi0ygous for genes on this chromosome. #he correct option is the only one that accurately identifies the term for males having only one chromosome. &#S" 1
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/-. ales are more often affected by which type of o f genetic disease? a. Sexlin6ed dominant c. Sexlin6ed b. Sexinfluenced d. Sexlin6ed recessive !S" D
ales are more fre%uently affected by lin6ed recessive diseases$ with the difference becoming more pronounced as the disease becomes rarer. #he #he correct option is the only one that is a characteristic of a maledominate disease. &#S" 1
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/8. !n lin6ed recessive disease can s6ip generations because " a. (emales are hemi0ygous for the chromosome. b. #he disease can be transmitted through female carriers. c. others cannot pass lin6ed genes to their sons. d. #hese diseases need only one copy of the gene in females. !S" ,
S6ipped generations are often observed in lin6ed recessive disease pedigrees because the gene can be transmitted through female carriers. ales are hemi0ygous for genes on the chromosome. (athers cannot pass lin6ed genes to their sons. lin6ed recessive diseases are observed significantly more often in males than in females$ because males need only one copy of the gene to express the disease. &#S" 1
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/9. #he presence of a 0ygote having one chromosome with the normal complement of genes and
one with a missing gene is characteristic of which genetic disorder? a. 5ri du chat c. Elinefelter syndrome b. Down syndrome d. #urner syndrome !S" !
#his description is only accurate for 5ri du chat syndrome. &#S" 1
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/*. ! child with which genetic disorder has a characteristic cry? a. Down syndrome c. #urner syndrome b. Elinefelter syndrome d. 5ri du chat !S" D
5ri du chat$ which literally means cry of o f the cat$H describes the characteristic cry of the affected child. #he correct option is the only one with the characteristic cry. &#S" 1
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/>. Ahich statement is true regarding true regarding lin6ed recessive conditions? a. Such diseases use males as phenotypical carriers. b. #hese conditions are passed from affected father to all of his female children. c. /8C of an affected individual;s grandsons will be affected. d. 5ystic fibrosis is an example of such a condition. !S" ,
lin6ed recessive conditions are passed from an affected father to all of his daughters$ who$ as phenotypically normal carriers$ transmit it to approximately one half of their sons$ who are affected. 5ystic fibrosis is an autosomal dominant do minant disease.
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/@. D! formation formation occurs in which of the cell;s structures? structures? a. ucleus c. 7rganelle b. 5ytoplasm d. embrane !S" !
D! is formed and replicated only in the cell nucleus. &#S" 1
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):. Ahat is the ris6 for the recurrence of autosomal do minant diseases? a. 1:C c. 8:C b. ):C d. *:C !S" 5
#he recurrence ris6 for autosomal dominant diseases is usually 8:C. &#S" 1
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)1. !n individual;s genetic ma6eup is referred to as his or her" a. &henotype c. 2etero0ygous locus b. Genotype d. 2omo0ygous locus !S" ,
!n individual;s genotype is his or her genetic ma6eup. #he correct option is the on ly one that accurately defines a person;s genetic ma6eup. &#S" 1
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MULTIPLE %E&PO'&E
)/. Ahich disorders have similar modes of inheritance? (Select all that apply.) a. 5ri du chat syndrome b. Duchenne muscular dystrophy c. &olycystic 6idney disease d. Down syndrome e. ,ec6er muscular dystrophy !S" ,$ '
,ec6er muscular dystrophy and Duchenne muscular dystrophy are the only options that are lin6ed recessive disorders. &#S" 1
R'(" &age 18>
)). #he 6ey to accurate D! replication depends on which complementary base pairs? (Select all
that apply.) a. !denine with thymine b. !denine with guanine c. Guanine with cytosine d. 5ytosine with thymine e. Guanine with thymine
!S" !$ 5
#he consistent pairing of adenine with thymine an d of guanine with cytosine$ 6nown as complementary base pairing$ is the 6ey to accurate D! replication. #he correct options are the only ones that accurately identify complementary base pairs. &#S" 1
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)-. 5hromosomal abnormalities are the leading 6nown cause of" (Select all that apply.) a. ental illness b. ental retardation c. (etal miscarriage d. 5ardiovascular disease e. Respiratory disorders !S" ,$ 5
5hromosome abnormalities are the leading 6nown cause of mental retardation and miscarriage. #he correct options are the only ones that accurately identify disorders that related to chromosomal abnormalities. &#S" 1
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)8. 'xamples of prenatal diagnostic studies include" (Select all that apply.) a. 5horionic villus sampling 35S4 b. !mniocentesis c. 5arrier screening d. &reimplantation genetic diagnosis 3&GD4 e. Drugsensitivity testing !S" !$ ,$ ,$ D
&renatal testing is conducted before or during the pregnancy but not once labor begins. Such diagnostic studies include amniocenteses$ 5S$ and &GD. #he correct options are the only ones that are exclusively used during the prenatal period. &#S" 1
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)9. #he advantage derived from human genome se%uencing on genetic disorders focuses on"
(Select all that apply.) a. Identification of the mutated gene b. Reversal of the mutation c. Diagnosis of the existing disorder d. !ppropriate treatment e. &revention of the disorder !S" !$ 5$ 5$ D
#he complete human genome se%uence will facilitate gene identification$ diagnosis$ and disease treatment. #he reversal of a mutation is not possible. #he mapping has no effect on preventing a genetic disorder. &#S" 1 M(TCHI'G
R'(" &age 19:
Match the genetic terms with the corresponding corresponding diseases. erms erms may be used more than once. JJJJJJ !. !utosomal dominant JJJJJJ ,. !utosomal recessive recessive JJJJJJ 5. lin6ed dominant JJJJJJ D. lin6ed recessive )*. )>. )@. -:.
5ystic fibrosis Duchenne muscular dystrophy Sic6le cell disease 2untington disease
)*. !S" S5" )>. !S" S5" )@. !S" S5" -:. !S" S5"
, &#S" 1 R'(" &age 18Is an important important example of an autosomal recessive recessive disease is cystic fibrosis. fibrosis. D &#S" 1 R'(" &age 18> Is an important important example of an lin6ed recessive recessive disease is Duchenne muscular muscular dystrophy. dystrophy. , &#S" 1 R'(" &age 1)9 + ,ox -1 Is an important important example of an autosomal recessive recessive disease is sic6le cell disease. disease. ! &#S" 1 R'(" &age 18!nother well6nown well6nown autosomal autosomal dominant dominant disease is 2untington 2untington disease. disease.
