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103 Cards in this Set
- Front
- Back
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What is your opinion? DM patients have inherited expanded a CTG allele from a parent with a normal allele (5-30 CTG repeats).
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False
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What is your opinion? Mitotic instability of the trinucleotide repeat throughout life is responsible for 50% of patients showing a clinical progression of disease symptoms.
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True
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What is your opinion? The trinucleotide expansion causes an amplification of mRNA synthesis as a consequence of hypomethylation
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False
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In Myotonic Dystrophy there are two phenotypes, the classical adult onset phenotype and the congenitally affected phenotype. What best describes the reason behind the two different phenotypes seen in the same family even though the mutation is inherited?
This disease is characterized by locus heterogeneity. The larger the expansion, the earlier the age of symptom onset. Subsequent generations present with symptom-onset at progressively older ages. This disease is characterized by variable expressivity |
The larger the expansion, the earlier the age of symptom onset.
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What is your opinion? Patients born of affected fathers are more severely affected than those born of affected mothers.
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False
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A father with myotonic dystrophy has three daughters who are affected and two sons who are unaffected. The three daughters have six sons of which four are affected and two are not, and four daughters of which two are affected and two are not. What type of mutation is suggested from this description?
Autosomal recessive Autosomal dominant X-linked recessive X-linked dominant |
Autosomal dominant
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Myotonic dystrophy may show increasing severity and earlier age of onset in successive generations. This phenomenon is known as
Compound heterozygosity Locus heterogeneity Incomplete penetrance Anticipation Variable expressivity |
Anticipation
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Treatments for MD
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There are no treatments for Myotonic Dystrophy.
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dystrophia myotonica is also known as
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Steinert's disease
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what is the mode of inheritance of Myotonic Dystrophy
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Autosomal Donimant
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What is Myotonia ?
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Muscle contraction but does not relax
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What are some symptoms of myotonic dystrophy?
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Mental deciency
Hair loss Cataracts |
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What is the expressivity of myotonic dystorphy?
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variable expressivity
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Is MD congenital or adult onset?
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Both
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Classical Adult Onset of MD?
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Progressive muscle weakness
Wastage and stiffness Heart problems Digestive problems Diabetes Increased sleeping (hypersomnia) Mental impairment premature balding Reduced fertility Breathing problems Testicular wastage |
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Congenitally affected of MD?
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Breathing difficulties
Initial hypotonia Feeding Difficulties Progression in skills possible until age 5 Delays in Milestones Speech Problems Delays in Toilet Training |
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What gene and what chromosomes are affected in MD?
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DM1- chromosome 19
DM2- chromosome 3 |
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What is the difference between DM1 and DM2
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DM1 – 19q13.3
Protein kinase (skeletal muscle) Expansion located in the 3’ untranslated region of the gene 1992 DM2 –3q21 expansion located in intron 1 of the zinc finger protein 9 (ZNF9) gene (controls whether genes will be expressed or not) 1998 |
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for MD,
If there are too many repeats, the gene will be ______ . They will have _________ for this disease. |
Methylated
Anticipation |
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What is the Mechanism for MD?
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Reduced synthesis of mRNA
Reduced processing of mRNA Creation of hyperstable nucleosomes Hypermethylation |
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what are some DNA polymerase errors in MD?
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Slippage
Pausing Idiling |
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what is shuttering in MD?
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attachment and reattachment of replication enzymes in regions of repeated triplets
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How can one obtain Congenital MD?
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Polyhydraminos
Reduced fetal movements “fish”-shaped mouth (facial diplegia) Respiratory failure MR in 50-60% |
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A 25-year-old woman is a carrier of Duchenne muscular dystrophy (DMD). She and her husband, who is not consanguineous, are interested in having children. If the frequency of DMD in their population is 4/10,000, what is the probability that if they have a male child it will be affected?
1% 25% 50% The carrier status of the husband must first be assessed with an 18 exon PCR multiplex deletion test Due to the genetics of the disease, the husband cannot carry the trait; hence their children will be unaffected |
50%
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Duchenne muscular dystrophy is an X-linked recessive disorder. Assume that affected males with Duchenne muscular dystrophy do not survive to reproductive age, and females are all fertile. Which of the following is the BEST answer?
The mutation rate for this locus is equal to the loss of male alleles. Females carry equal numbers of mutant alleles. Treatments that affect survival in male to adults will have no effect on allele frequencies All of the above are correct. None of the above are correct |
The mutation rate for this locus is equal to the loss of male alleles.
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A boy with Duchenne muscular dystrophy (DMD) was born to parents with no family history of the disease. The most likely explanation for this occurrence is:
a CGG expansion that resulted in the disruption of the promoter of the dystrophin gene. point mutation in the dystrophin gene. a recombination event in the dystrophin gene that gave rise to a frameshift mutation leading to an untranslatable mRNA. a translocation that resulted in the disruption of the dystrophin gene. |
a recombination event in the dystrophin gene that gave rise to a frameshift mutation leading to an untranslatable mRNA.
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The family below is segregating a mutation for Duchenne Muscular Dystrophy (DMD), a lethal X-linked recessive disorder. Filled symbols represent individuals affected with DMD. Individual III-1, 5 y.o., has muscle weakness and wasting, and has an abnormal muscle biopsy. Both III-1, and her sister III-2, aged 1 y.o., have normal karyotypes. What is the risk that III-2 is a carrier for DMD?
0% 25% 50% 75% 100% |
50%
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A patient of yours is a girl with Duchenne muscular dystrophy, an X-linked recessive disorder. Which of the following could be responsible for this finding?
An X;autosome translocation Turner syndrome (45, X). Androgen insensitivity causing sex reversal in an individual with a 46, XY karyotype. All of the above |
All of the above
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Treatment for DMD
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Preservation of muscle function
Physical therapy Bracing Orthopedic surgery |
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does DMD directly present itself at birth?
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No
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who discovered DMD.
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Guillaume Duchenne
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what is the mode of inheritance for DMD?
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X linked recessive
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what is one characteristic of DMD in the legs?
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Pseudohypertrophy of the calves
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what percentage is DMD inherited and spontaneous?
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Spontaneous --30%
Inherited is 69-70% |
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around what age are most children wheel chair bound in DMD?
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age 13
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Explain what happens to the dystrophin in DMD?
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Without dystrophin for support, the cell embrane becomes permeable, so that extracellular components enter the cell, increasing the internal pressure until the muscle cell explodes and dies.
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what does dystrophin do?
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Anchors cytoskeleton to the membrane and maintains membrane integrity
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C terminis is deleted and can cause the protien to be destroyed .. Therefore, the protein does not reach the muscle and so forth.
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next
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what kind of mutation can cause DMD?
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deletions, or duplications
Frameshift and point mutations |
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In Becker MD, what kind of mutation occurs?
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In frame (change of codon)
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the dystrophin gene is located on the ______
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X chromosome
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What is the mode of inheritance in Myotonic Dystrophy
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autosomal dominant
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Which of the following statements is TRUE?
A. Duchenne and Becker Muscular Dystrophy represent locus heterogeneity. B. Myotonic Dystrophy is a disease represented by allelic heterogeneity. C. Duchenne Muscular Dystrophy is caused by a mutation in the dystrophin protein. D. Myotonic dystrophy is caused by a frameshift mutation. |
C. Duchenne Muscular Dystrophy is caused by a mutation in the dystrophin protein.
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Trinucleotide repeat diseases are characterized by premutations, and disease mutations. Each characterized by the size of the tinucleotide repeats. Which of the following best describes the phenotypes of individuals affected by these diseases?
A. Premutations can eventually progress to active disease. B. Age of onset increases with increasing size of the trinucleotide repeats. C. Severity of the phenotype increases with increasing size of the trinucleotide repeats. D. All of the above are correct. |
C. Severity of the phenotype increases with increasing size of the trinucleotide repeats.
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Which of the following is the definition of an obligate carrier?
A. An individual who is affected by an autosomal dominant mutation. B. An individual who is affected by an autosomal recessive mutation. C. An individual who expresses a phenotype only when a particular environment impacts gene expression abnormally. D. An individual who is clinically unaffected but who must carry a gene mutation based on analysis of the family history. |
D. An individual who is clinically unaffected but who must carry a gene mutation based on analysis of the family history.
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Muscle contraction followed by a decrease in the power to relax the muscle leads to muscle decay. What is your diagnosis?
A. Myotonic dystrophy B. Duchenne muscular dystrophy C. Becker muscular dystrophy D. None of these anwers are correct. |
Myotonic dystrophy
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Patients born of affected mothers are more severley affected on average than those born of affected fathers in Myotonic Dystrophy.
True False |
True
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Mitotic instability plays a role in the progressively worsening phenotype of Duchenne muscular dystrophy.
T/F |
False
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In which of the following genetic disorders whould you expect to find the highest proportion of patients with a nuw mutation (not present in either parent)?
A. Autosomal dominant B. Autosomal recessive C. Trinucleotide repeat D. X-linked recessive |
D. X-linked recessive
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An 18-year-old woman with healthy parents showed muscle weakness. Her brother had been diagnosed with an X-linked recessive muscular dystrophy caused by an allele that impairs production of dystrophin, a component of the sarcolemmal cytoskeleton. About one third of such cases are new mutations. What is the LEAST likely cause of the woman's muscle weakness?
A. X-autosome translocation B. Turner syndrome. C. Somatic mutation D. Unfortunate (extreme) lyonization. |
C. Somatic mutation
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Which of the following does not belong with the others?
A. Uni-nucleated B. Cardiac C. Striated D. Voluntary |
D. Voluntary
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The interaction of which two proteins in muscles is responsible for contraction?
A. myosin and tropomyosin B. myosin and actin C. actin and toponin D. troponin and tropomyosin |
B. myosin and actin
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Which term is the largest subdivision in this group?
A. fiber B. fibril C. filament D. actin |
A. fiber
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Too much acetylcholinesterase in the synaptic cleft would result in:
A. Decreased acetylcholine production by the motor neuron B. Innervation of the muscle fiber C. Excessive, continuous stimulation of the muscle fiber D. Inability of the motor neuron to stimulate the muscle fiber |
D. Inability of the motor neuron to stimulate the muscle fiber
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Which of the following is the main function of the pacemaker?
A. controls the function of the cardiac muscles B. controls the function of involuntary muscles C. controls the function of voluntary muscles D. controls the function of smooth muscles |
A. controls the function of the cardiac muscles
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The long bones can grow in diameter and in length during periods of growth. Which of the following best describes the part of the bone responsible for this growth?
A. Diaphysis is responsible for increase in bone diameter and periosteum is responsible for increase in bone length. B. Epiphysis is responsible for increase in bone diameter and peiosteum is responsible for increase in bone length. C. Periosteum is responsible for increase in bone diameter and epiphyseal disk is responsible for increase in bone length. D. None of the above is correct |
C. Periosteum is responsible for increase in bone diameter and epiphyseal disk is responsible for increase in bone length.
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What is the basic function of the osteocyte?
A. forms bone matrix by secreting collagen B. maintains daily cellular activities C. important in repair of bone D. function in bone resorption |
B. maintains daily cellular activities
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The epiphysis:
A. Is the end of long bones. B. The outer, fibrous, protective covering that contain nerves and blood vessels that nourishes the bone. C. The innermost part of the bone where blood cells are produced. D. Is the substance that gives bone its hardness and is primarily composed of calcium and phosphates. |
A. Is the end of long bones.
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Which of the following is not a hormone that is necessary for normal bone growth and development?
A. Human growth hormone B. Calcitonin C. Estrogen D. Retinol |
D. Retinol
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The early embryonic skeleton, before ossification, is made up of cartilage and connective tissue.
True False |
True
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Which of the following does not belong with the others?
A. Uni-nucleated B. Cardiac C. Striated D. Voluntary |
D. Voluntary
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The interaction of which two proteins in muscles is responsible for contraction?
A. myosin and tropomyosin B. myosin and actin C. actin and toponin D. troponin and tropomyosin |
B. myosin and actin
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Which term is the largest subdivision in this group?
A. fiber B. fibril C. filament D. actin |
A. fiber
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Too much acetylcholinesterase in the synaptic cleft would result in:
A. Decreased acetylcholine production by the motor neuron B. Innervation of the muscle fiber C. Excessive, continuous stimulation of the muscle fiber D. Inability of the motor neuron to stimulate the muscle fiber |
D. Inability of the motor neuron to stimulate the muscle fiber
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Which of the following is the main function of the pacemaker?
A. controls the function of the cardiac muscles B. controls the function of involuntary muscles C. controls the function of voluntary muscles D. controls the function of smooth muscles |
A. controls the function of the cardiac muscles
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The long bones can grow in diameter and in length during periods of growth. Which of the following best describes the part of the bone responsible for this growth?
A. Diaphysis is responsible for increase in bone diameter and periosteum is responsible for increase in bone length. B. Epiphysis is responsible for increase in bone diameter and peiosteum is responsible for increase in bone length. C. Periosteum is responsible for increase in bone diameter and epiphyseal disk is responsible for increase in bone length. D. None of the above is correct |
C. Periosteum is responsible for increase in bone diameter and epiphyseal disk is responsible for increase in bone length.
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What is the basic function of the osteocyte?
A. forms bone matrix by secreting collagen B. maintains daily cellular activities C. important in repair of bone D. function in bone resorption |
B. maintains daily cellular activities
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The epiphysis:
A. Is the end of long bones. B. The outer, fibrous, protective covering that contain nerves and blood vessels that nourishes the bone. C. The innermost part of the bone where blood cells are produced. D. Is the substance that gives bone its hardness and is primarily composed of calcium and phosphates. |
A. Is the end of long bones.
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Which of the following is not a hormone that is necessary for normal bone growth and development?
A. Human growth hormone B. Calcitonin C. Estrogen D. Retinol |
D. Retinol
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The early embryonic skeleton, before ossification, is made up of cartilage and connective tissue.
True False |
True
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Muscle that is uninucleated and involuntary
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cardiac
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Two major regulatory proteins in muscle tissue
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Toponin and tropomyosin
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A model that describes the binding of actin and myosin and the shortening of muscle fibers that occurs when the thick and thin filaments slide past each other.
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Sliding filament model
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What is the basic unit of contraction?
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Sarcomere
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This enzyme in the synaptic cleft degrades the neurotransmitter which binds to receptors on skeletal muscle fibers and opens ligand-gated sodium channels in the cell membrane.
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Acetylcholinesterase
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The process of converting cartilage and membranes to bone
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Ossification
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All the bones in the body and the tissues that connect them.
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Skeletal system
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The ends of long bones
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Epiphyses
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Substance composed primarily of calcium and phosphates that gives bone its hardness
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Hydroxyapatite
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Layer of dense irregular connective tissue that protects, nourishes and allows bone growh in diameter
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Periosteum
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Myotonic Dystophy mutation
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Trinucleotide repeat expansion
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Muscular Dystophy mutation
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Frameshift (nonsense) mutation
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In this disease muscle is replaced by fat and connective tissue
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Duchenne muscular dystrophy
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Multiple phenotype caused by a single genetic mutation is called
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Pleiotrophy
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Mutation in the Ellis van Creveld sydrome gene caused also causes an autosomal dominant syndrome called Weyers acrodental dysostosis. This phenomonen of having two syndromes caused by mutations in the same gene is called.
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Allelic heterogeneity
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Caused by small populations that are reproductively isolated
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Founder Effect
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A hole that occurs in the atrium wall.
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Atrium septation
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Fibrillin is found in what type of tissue?
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Connective tissue
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The primary defect in Marfan syndrome affects what kind of protein?
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Structural protein fibrillin
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Individuals with Marfan Syndrome have mild symptoms and others have severe symptoms. This is called:
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Variable expressivity
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If patients with Marfan syndrome have a reproductive fitness of 0.9, a constant prevalence rate would indicate:
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90% are due to inherited mutations and 10% are due to new mutations
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2. What are the different types of myotonic dystrophy?
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1)Classical adult onset
2)Congenital onset |
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There are currently two known types of adult onset DM, both identifiable by DNA analysis
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• Myotonic dystrophy type 1 (DM1), also known as Steinert's disease. DM1 has a congenital form that can severely affect babies and a childhood onset form.
• Myotonic dystrophy type 2 (DM2), commonly referred to as PROMM or proximal myotonic myopathy. |
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Name the class of MD mutations? Explain each
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Permutation--38-49 repeats
Mild---50 to 150 repeats Classical--100-15000 repeats Congenital---1000 to 2000 repeats |
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1. What is the inheritance mode of Marfan syndrome.
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Autosomal dominant
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2. Which gene mutation will result in Marfan Syndrome
What is major function of this gene? |
FBN1 gene is defective which is located on Chromosome 15q2
Encodes a connective protein called fibrillin1. |
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In Marfan syndrome, what is the main cause of death ?
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the chemical makeup of the connective tissue isn't normal therefore many of these structures aren't as stiff as they should be
• The connective tissue provides substance and support to tendons, ligaments, blood vessel walls, cartilage, heart valves and many other structures |
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name some of the major symptoms of Marfan syndrome
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• Eyes (Ocular system)
o Severe nearsightedness (myopia) o Dislocated lens of the eye o Detached retina o Early glaucoma o Early cataracts • Connective Tissue of the Skeletal System o Long arms and legs o Tall and thin body type o Curvature of the spine (scoliosis or kyphosis) o Chest sinks in (pectus excavatum) or sticks out/pigeon breast (pectus carinatum) o Long, thin fingers o Flexible joints o Flat feet • Heart and Blood Vessels (Cardiovascular system) o Enlarged or bulging aorta, the main blood vessel that carries blood from the heart (aortic dilation or aneurysm) o Separation of the layers of the aorta that can cause it to tear (aortic dissection) o “Floppy” mitral valve (mitral valve prolapse – MVP) • Other o Stretch marks not associated with being overweight or pregnancy. o Sudden collapse of lung o The connective tissue that surrounds the spinal cord loosens and stretches out (dural ectasia) |
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5. What is the major cause of death of patients with Marfan syndrome
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In Marfan syndrome, the wall of the aorta gradually weakens and stretches (aortic dilation). Eventually, this can cause a tear (dissection) in the lining of the aorta. Blood can leak out through the tear into the aortic wall, sometimes causing a rupture that allows blood to leak into the chest or abdomen. If not detected and treated, these complications can cause sudden death.
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What is the inheritance mode of Ellis-Van Creveld Syndrome?
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rare autosomal recessive
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Ellis-Van Creveld Syndrome is also called Chondroectodermal dysplasia. Please list five of major symptoms of this disorder.
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The symptoms of Ellis Van Creveld syndrome are usually apparent at birth. These include:
Short stature - adults average about 109-155 cm tall (just under 4 feet to about 5'3") Short forearms and legs Extra fingers and toes Narrow chest with short ribs Malformed pelvis Hyperdontia – natal teeth Ectodermal dysplasia - Nail dysplasia Heart defect in 50 – 60% of those affected |
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. What is founder effect
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Founder Effect is an extreme example of genetic drift. Genetic drift contradicts Darwin's dictum about the "survival of the fittest"
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Which gene mutation will result in Ellis-Van Creveld Syndrome? Where is this gene located in chromosome?
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Ellis-van Creveld syndrome is caused by a mutation in the EVC gene, as well as by a mutation in a nonhomologous gene, EVC2, located close to the EVC gene in a head-to-head configuration. By positional cloning, the gene was identified. The EVC gene maps to the chromosome 4 short arm. The function of a healthy EVC gene is not well understood at this time. More than 20 mutations in the EVC gene have been reported to cause Ellis-van Creveld syndrome.
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