Ch9: Genetics Flashcards
(277 cards)
1
Q
Disorders related to single gene usually follow what inheritance pattern?
A
Mendelian
2
Q
Two types of single gene mutations?
A
- Mendelian
2. Non-classic inheritance
3
Q
What is a mutation?
A
Permanent change in DNA of an organism
4
Q
What is a genome mutation?
A
Loss or gain of whole chromosomes
5
Q
What is a chromosomal mutation?
A
Structural changes to chromosomes
6
Q
What are gene mutations?
A
Change at gene level
7
Q
What are the two categories of gene mutations?
A
- Point mutations
2. Frameshift mutation
8
Q
What are the two types of point mutations?
A
- Nonsense mutation
2. Missense mutation
9
Q
What are the two types of frameshift mutations?
A
- Insertions
2. Deletions
10
Q
Trinucleotide repeat mutations occur within coding or non-coding regions?
A
Both
11
Q
What is the longest chromosome?
A
Chromosome 1
12
Q
Which is the shortest chromosome?
A
Chromosome 22
13
Q
What is a balanced reciprocal translocation?
A
exchange of material between nonhomologous chromosomes
14
Q
What is a Robertsonian translocation?
A
nonreciprocal translocation involving two homologous (paired) chromosomes or non-homologous chromosome
15
Q
What is an isochromosome?
A
chromosome that has lost one of its arms and replaced it with an exact copy of the other arm.
16
Q
What is a paracentric inversion?
A
reversal of the normal order of genes in a chromosome segment involving only the part of a chromosome at one side of the centromere
17
Q
What is a pericentric inversion?
A
inversions include the centromere and there is a break point in each arm
18
Q
How does a ring chromosome form?
A
chromosome whose arms have fused together to form a ring
19
Q
Hemoglobin S is the result of what type of mutation?
A
Point mutation causing a missense mutation
20
Q
What is the exact change in hemoglobin S?
A
GAG becomes GUG which encodes valine instead of glutamic acid
21
Q
What type of mutation is beta thalassemia?
A
Point mutation causing a nonsense mutation.
22
Q
What type of mutation is the ABO O allele?
A
Frameshift mutation from a single base deletion
23
Q
Hexosaminidase A/Tay Sachs is the result of what?
A
Frameshift mutation caused by four base insertion
24
Q
Cystic fibrosis is the result of what?
A
Three base deletion that does NOT cause a frameshift
25
Fragile X syndrome is the result of what?
CGG triplet repeat
26
Friederich ataxia is the result of what?
GAA triplet repeat
27
Huntington's disease is the result of what?
CAG triplet repeat
28
Myotonic dystrophy is the result of what?
CTG repeat
29
What is myoclonus epilepsy the result of what?
12 repeat: CCCCGCCCCGCG
30
What is a mendelian disorder?
Genetic disorder of large effect caused by a single gene mutation
31
What is the one common X-linked dominant disorder?
Vitamin D resistant rickets
32
3 mendelian disorder types
1. Autosomal dominant
2. Autosomal recessive
3. X-linked recessive
33
Autosomal dominant is a disorder manifested in what genotype?
heterozygous
34
When do autosomal dominant disorders present?
Onset delay until adulthood
35
Can autosomal dominant disorders spontaneously occur in the germline?
yes
36
What modifies the expression of autosomal dominant genotype?
1. Reduced penetrance
| 2. variable expressivity
37
What does the mutated gene usually encode for in autosomal dominant?
Control points in metabolic pathways
| Key structural proteins
38
Autosomal recessive disorders are manifested only in what genotype?
Homozygous state
39
Siblings in AR disease have what chance of being affected?
| Of being carriers?
1 in 4 chance of being affected
1 in 2 chance of being a carrier
40
If a low frequency gene mutation begins to appear, what does this suggest?
Population is consanguineous
41
Which has more uniform expression, autosomal dominant or recessive?
Recessive
42
Is complete penetrance common in AR?
Yes
43
When does onset of autosomal recessive occur?
Early in life
44
Can spontaneous mutations occur of autosomal recessive genes?
Yes, but takes awhile to present (several generations)
45
Autosomal recessive genes usually encode for what?
Enzyme
46
What protects us against a heterozygous autosomal recessive genotype?
The normal gene will make enough enzyme to be at functioning level
47
X-linked recessive disorders require how many abnormal X chromosomes in females?
2
48
X-linked recessive disorders require how many abnormal X chromosomes in males?
1
49
Who transfers the X-linked recessive gene?
Heterozygous female
50
Who receives the X-linked recessive gene?
Sons (1 in 2 chance)
51
What can lead to expression of an x-linked recessive phenotype in females?
Lyonization
52
How does an affected father of an x-linked recessive disorder pass on the mutation?
All daughters will be carriers
53
What is codominance?
When two different gene alleles are fully expressed together.
54
What are examples of codominance? (2)
1. Histocompatibility
| 2. Blood groups
55
Codominant Mendelian disorders occur when?
When both normal and mutant gene are fully expressed
56
What are examples of some codominance disorders? (2)
1. Thalassemias
| 2. Sickle cell anemia
57
What is penetrance?
The measure of how much a Mendelian disorder is phenotypically expressed.
58
What is it called when all individuals with a mutation express the phenotype?
Complete penetrance
59
What is it called when some affected individuals are phenotypically normal?
Reduced penetrance
60
What is variable expressivity?
Degree of phenotypic change seen in affected individuals.
61
Example of variable expressivity?
Neurofibromatosis. Some individuals have cafe au lait macules and some have widespread neural tumors and deformities
62
What is polymorphism?
Existence of more than one normal allele of a gene.
63
What are examples of polymorphisms? 2
1. histocompatibility genes
| 2. Blood group genes
64
What are the most common form of polymorphisms?
SNP's
65
SNP's occur in coding regions how often?
1%
66
What is pleiotropism?
Ability of a single mutation to have more than one phenotypic effect?
67
What are two examples of pleiotropism?
1. Marfan syndrome
| 2. Neurofibromatosis
68
What is genetic heterogeneity?
Ability of different gene muations to cause the same phenotypic change.
69
Example of genetic heterogeneity? (2)
1. Retinitis pigmentosa
| 2. Childhood deafness
70
What is the phenotype?
Physical appearance or biochemical characteristics as distinguished from its genotype
71
What is genotype?
genetic makeup of an organism as distinguished from its physical characteristics
72
Two types of non-protein producing genes?
1. miRNA
| 2. lcRNA
73
What are miRNA?
small RNA molecules that are further shortened, unwound to single RNA strands, and coupled with proteins.
74
The RNA-induced silencing complex interacts with what?
| To what effect?
miRNA
| Cleave or suppress translation of mRNA
75
If child has an autosomal dominant mutation but neither parent does, what happened?
Spontaneous mutation
76
Are autosomal dominant mutations usually loss of function or gain of function?
Loss
77
Two main characterizations of AD disorders?
1. variable expressivity
| 2. reduced penetrance
78
Autosomal dominant disorders in the nervous system include? 4
1. neurofibromatosis (von Recklinghausen)
2. Huntington's diseas
3. myotonic dystrophy
4. tuberous sclerosis (bourneville's disease)
79
AD disorders in urinary system?
Adult polycystic kidney disease
80
Gastrointestinal AD disorder?
Familial polyposis coli
81
Hematopoietic AD disorder? 2
1. hereditary spherocytosis
| 2. von willebrand disease
82
Neurofibromatosis Type 1 is known as what?
von Recklinghausen disease
83
What percentage of NF-1's are spontaneous mutations?
50%
84
Which is more common, Type 1 or Type 2 NF?
Type 1 NF
85
What is the cause of NF-1
Defect of NF-1 gene on chromosome 17q11
86
NF-1 is what type of gene?
| What does it produce?
Tumor suppressor gene
| Neurofibromin
87
Clinical features of NF-1? 3
1. Neurofibromas
2. Cafe au lait macules
3. Lisch nodules
88
What are the 4 types of neurofibromas in NF-1? Which is the one to watch for?
1. cutaneous
2. subcutaneous
3. deep tissue
4. plexiform: (WATCH THIS ONE)
89
Malignant tumors show up in NF-1 what percentage of the time?
What other things can NF-1 produce? (4)
3%
Skeletal abnormalities
Solid malignancies
CML
Reduced intelligence
90
What are lisch nodules?
Brown irregular discolorations in the iris
91
NF-2 has what clinical features? (5)
1. Bilateral acoustic neuromas
2. Multiple meningiomas
3. Neurofibromas
4. Cafe au lait macules
5. NO Lisch nodules
92
NF-2 gene is found where?
| What does it produce?
Ch 22
| Merlin
93
Hereditary spherocytosis is developed how?
auto-hemolytic anemia characterized by the production of red blood cells that are sphere-shaped rather than bi-concave disk shaped (donut-shaped), and therefore more prone to hemolysis
94
AD skeletal disorders include what? 4
1. marfan
2. ehlers-danlos
3. osteogenesis imperfecta
4. Achondroplasia
95
Metabolic AD disorders? (2)
1. familial hypercholesterolemia
| 2. acute intermittent porphyria
96
Marfan syndrome is due to what defective protein?
Where is this gene found?
Function of this protein normally?
Fibrillin
Ch 15
Provide stability to elastic tissue
97
Overall, Marfan is a disorder of what?
CT
98
What do you see in marfan syndrome? 7
1. aortic dilatation leading to valve incompetence
2. cystic medial necrosis leading to aortic dissection
3. Mitral valve prolapse
4. Increased stature
5. Arachnodactyly
6. Dislocated lens (ectopia lentis)
7. Premare aging due to mucopolysaccharide deposition
99
Ehlers-danlos syndrome involves how many diseases?
12 variants
100
Ehler-danlos syndrome exhibits what type of inheritance?
All three
101
What collagen pathways are mutated in Ehlers-Danlos? 3
Type IV
Type VI
Type VII
102
How does ehler danlos present?
1. Very stretchable skin
2. hypermobile joints
hypotonia at birth
3. epicanthal folds and blue sclerae in eyes
103
What people do you see with Ehlers-Danlos?
Contortionists
104
Which is the most common mendelian disorder?
Familial hypercholesterolemia
105
What is the main cause of familial hypercholesterolemia?
Defective LDL receptor which regulates cholesterol metabolism
106
Clinical manifestations of familial Hypercholesterolemia?
High levels of total and LDL cholesterol
107
What are the five mutations that can result in hypercholesterolemia?
Class I: Can't synthesize LDL receptor
Class II: Can't transport LDL receptor to membrane
Class III: Can't put LDL receptor into plasma membrane
Class IV: Can't get LDL receptors to cluster in coated pit
Class V: Can't recycle LDL receptors after use
108
Xanthomas are representative of what?
Hypercholesterolemia familial
109
Xanthelasma are representative of what?
Somewhat with hypercholesterolemia familial
110
Cystic fibrosis is what type of disorder?
Autosomal recessive systemic disorder of exocrine glands that affects mucus-secreting and eccrine glands
111
The defects in CF involve what abnormality?
| What does this result in?
Electrolyte abnormalities
Abnormally thick mucus that can cause obstruction of excretory ducts which is really harmful in lungs and pancreas
112
What reputation does CF have?
Most common fatal autosomal recessive disease affecting the Caucasian population
113
Why does CF occur?
Defect in c-AMP-regulated ion transport across apical membranes of affected epithelial cells
114
How does CF affect the sweat glands?
| What does this mean clinically?
Failure of resorption of chloride in duct epithelial cells which results in high chloride levels in sweat.
the pilocarpine sweat test in which a value of sweat chloride above 60 mEq/L (normal being 10 mEq/L), along with symptoms consistent with CF, is essentially diagnostic
115
How does CF affect the lungs and pancreatic duct cells?
Failure to transport chloride into lumen of airways and ducts which is coupled with increase sodium resorption which results in very thick viscid secretions that begin to obstruct. In the lungs this provides great environment for pseudomonas
116
The CF gene has been localized to where?
| What is the gene product?
Chromsome 7 long arm
| CF transmembrane conductance regulator (CFTR) which is a chloride channel that can't be activated by cAMP
117
Heterozygous CF patients will display what?
Resistance to diarrheal diseases like cholera
118
How many CF mutations exist?
| Which is the most common at 70%?
300
| Deletion of a 3 base pair encoding phenylalanine (Delta F508)
119
How does CF affect the pancreas early on? 2
What follows? 3
What happens later?
1. Cystic dilatation
2. Direct plugging of exocrine glands and ducts with eosinophilic secretions
Acinar atrophy with rupture
Inflammation
Progressive fibrosis
Fatty and fibrous replacement of exocrine pancreas that spares islet cells usually
120
How does CS begin in lungs? (2)
What follows?
What does long term CF give rise to? (3)
1. Plugging of submucosal tracheal mucous glands and ducts
2. Bronchioles become distended with mucus
Atelectasis
Emphysema
Chronic bronchitis
Bronchiectasis
Lung abscesses
121
How does cystic fibrosis begin in liver?
| What is seen resulting from this
Bile duct hyperplasia due to mucus plugging bile canaliculi
Focal biliary cirrhosis and diffuse hepatic nodularity
122
CF in salivary glands show what?
Glandular dilatation and atrophy
123
CF in the reproductive glands show what?
Obstruction of Wolffian duct derivatives like epididymis and vas deferens leads to azoospermia and infertility in 95% of males
124
15% of infants with CF present with what?
| What happens in this?
Meconium ileus
Obstruction of terminal ileus with risk of perforation and peritonitis
125
CF is discovered when?
| Because of what?
between 12 months and 2 years
Malabsorption symptoms due to pancreatic insufficiency
126
What causes 80 to 90% of deaths in CF? 2
Obstructive pulmonary disease
| Persistent pulmonary infections
127
What is current therapy for CF? 3
How long can CF patients live now?
What is in the works for CF therapy?
1. Pancreatic enzymes
2. Fat soluble vitamins
3. Antibiotics for pulmonary infections
50% live past 31
Normal DNA injected into respiratory epithelial cells
128
Sickle cell anemia results from what type of mutation?
Missense
129
Inheritance of a single mutant sickle cell alelle results in what?
Sickle cell Trait
130
Sickle cell trait gives the person what?
Protection to malaria
131
Sickle cell disease forms can also include what? (2)
1. Sickle-hemoglobin C disease
| 2. Sickle-beta thalassemia
132
How many genes make up hemoglobin?
| Which chromosomes
4 alpha genes (2 HBA1 and 2 HBA2): Ch 16
| 2 beta genes: Ch 11
133
Hemoglobin A has what chains?
| What percentage of adult Hb is this form?
2 alpha and 2 beta
95%
134
Hemoglobin A2 has what chains?
| What percentage of adult Hb is this form?
Two alpha
| Two delta
135
Hemoglobin F has what chains?
Two alpha
| Two gamma
136
Hemoglobin S has what chains?
Two alpha
| Two mutated Beta
137
Hemoglobin AS has what chains?
Two alpha
One beta
One mutated Beta
138
What hemoglobin genotypes are in sickle cell trait?
60% HbA
| 40% HbS
139
Hemoglobin C has what chains?
Two alpha
| Two mutated beta
140
Hemoglobin SC has what chains?
Two alpha
1 Beta S mutation
1 Beta C mutation
141
Hemoglobin E has what chains?
Two alpha
| Two mutated beta (E mutation)
142
How do sickle cells affect the blood?
1. Increased adhesion causes infarcts in the kidney
| 2. Increased hemolysis in spleen that can result in autosplenectomy
143
Phentylketonuria is what type of inheritance?
PKU
144
PKU affects what people?
Scandinavian descent
145
PKU is due to a severe lack of what enzyme?
Phenylalanine hydroxylase causing hyperphenylalaninemia and PKU
146
No phenylalanine hydroxylase means what?
Can't convert phenylalanine to tyrosine so metabolites form in urine and sweat
147
How does PKU present at birth?
Doesn't appear at birth, but within a few weeks have increasing plasma levels of phenylalanine and toxic metabolites
148
Treatment of PKU is what?
Restrict ingestion of foods with phenyalanine during infancy and childhood
149
PKU results in what within 6 months if it is not treated? 4
Mental retardation
Seizures
Eczema
Decreased pigementation
150
PKU screening is performed when? What test?
Neonatal by the Guthrie test
151
What is maternal PKU results from what? 2
1. teratogenic effects of phenylalanine
2. metabolites that cross the placenta in a female adults with PKU who don’t follow a phenylalanine restricted diet during pregnancy
152
In PKU in adults, do the affected adults show symptoms?
| Can they give up low Phenylalanine treatment?
Affected adults have no apparent adverse affects from elevated levels of phenylalanine and its metabolites after CNS development is complete
Yes, but NOT if pregnant
153
Maternal PKU anomalies include? (6)
```
Cardiac defects
Microcephaly
Low birth weight
Mental retardation
Slow development
Language deficits
```
154
98% of PKU is due to a mutation in what?
PAH
155
Galactosemia is what inheritance?
Autosomal recessive
156
Galactosemia is the ability to do what?
Convert galactose to glucose because do not have galactose-1-phosphate urydil transferase
157
Clinical presentation of galactosemia? (6)
1. hepatomegaly and jaundice
2. Cataracts
3. Non-specific CNS changes
4. failure to thrive
5. vomiting
6. diarrhea
158
How can galactosemia be prevented?
No galactose in diet until age 2
159
Lysosomal storage disease results from what?
Lack of lysosomal enzymes essential for normal function of lysosomes results in lysosomes storing non-metabolized products
160
Example of glycogenoses?
Pompe
161
Example of sphingolipidoses?
Tay-Sachs
162
Example of sulfatidoses?
Gaucher
163
Example of mucopolysaccharidoses?
Hurler
164
Tay sachs results from what enzyme complex being mutated?
| What does this cause?
Deficiency of Hexosaminidase A alpha subunit
| GM2-ganglioside accumulation
165
The GM2-ganglioside accumulation of TaySachs is where?
| Main manifestation?
Neurons of CNS and ANS
Retinal cherry red spot
166
Tay-Sachs disease is most common with what population?
| When do they die?
Ashkenazi Jews
| Death by 2-3 years
167
What does Niemann Pick disease result from?
Accumulation of sphingomyelin and cholesterol
168
What types of Niemann-Pick are there?
Which is most common?
Which is most common in Ashkenazi?
A, B, C
C most common
A and B
169
Type A of Niemann Pick is known as what form?
| What symptoms? (4)
Severe infantile form
Neuronal death with resultant brain shrinkage
Retinal cherry spot
Hepatosplenomegaly and lymphadenopathy
Death at age 1-3
170
Type C Niemann Pick has what gene affected?
| What does this gene control?
NPC-1
| Cholesterol trafficking
171
Heterogeneous Niemann Pick Type C shows what? 3
Hydrops fetalis and still birth
Neonatal hepatitis
Chronic form with progressive neurologic damage
172
Gaucher disease is characterized by mutation in what gene?
| What does this lead to?
Glucocerebrosidase gene
| Decreased levels or activity of this enzyme
173
Three subtypes of Gaucher disease?
Type I
Type II
Type III
174
Type I gaucher disease is involved with what cells?
Mononuclear phagocytes, NOT the CNS.
175
What changes are common in Type I gaucher?
| Which population has it the most
Spleen and skeletal
| Eastern European Jews
176
What is Type II and Type III Gaucher's disease known as?
Type II: Infantile acute cerebral form
| Type III: Intermediate form
177
All forms of Gaucher have elevated levels of what enzyme?
Chitotriosidase
178
Type I Gaucher has what appearance under microscopy?
Crumpled tissue paper
179
Hunter and Hurler syndromes are examples of what?
Mucopolysaccharidoses
180
All mucopolysaccharidoses have what inheritance?
| The one exception?
Autosomal recessive
| Hunter: X-linked recessive
181
Common features of mucopolysaccharidoses? 4
Coarse facial features
Clouding of the corneas
Joint stiffness
Mental retardation
182
What is glycogenoses the result of?
metabolic defect in the synthesis or catabolism of glycogen
183
What are the three main types of Glycogenoses?
```
Hepatic type (von Gierke disease, type I)
Myopathic type (McArdle syndrome, type V)
Miscellaneous types (Pompe disease, type II)
```
184
Pompe is due to what deficiency?
lysosomal Acid maltase
185
Hepatic glycogen storage disease will cause what?
Feeling hungry and not nourished
186
Myopathic glycogen storage disease will cause what?
Muscle weakness
187
McArdle is due to what deficiency?
Phosphorylase
188
von Gierke's disease is due to what deficiency?
Glucose-6-phosphatase
189
Pompe has characteristics of what two sets of disorders?
1. glycogen storage
| 2. lysosomal storage
190
In pompe, what happens to the glycogen?
Accumulates in organs, especially the heart, and causes death
191
What is the heredity of alkatonuria?
Autosomal recessive
192
Alkaptonuria is caused by what?
lack of homogentisic oxidase causing build-up of homogentisic acid
193
In alkaptonuria, where does the homogentisic build up go?
1. Excreted in urine which will stain black upon staining
| 2. Ochronosis
194
What is ochronosis?
| where is this seen the most?
homogentisic acid binds to collagen in tissues imparting black-blue pigmentation to these tissues
ears, nose, cheeks, joints
195
Fragile X is different from the other x linked recessive diseases how?
It's seen as X-linked recessive and x-linked dominant. It's a triple nucleotide repeat that doesn't play by the rules.
196
What are all the possible disorders located on X chromosome
```
Duchenne Muscular Dystrophy
Becker Muscular Dystrophy
Hemophilia A & B
Glucose-6-phosphate dehydrogenase deficiency
Chronic granulomatous disease
Lesch-Nyhan syndrome
Diabetes insipidus
Fragile X syndrome
Ocular albinism
Chronic granulomatous disease
Menkes syndrome
Testicular feminization
X-linked SCID
X-linked agammaglobinulinemia
Fabry disease
Hunter Syndrome
```
197
Multifactorial inheritance results from what?
combined actions of environmental influences and the additive effects of two or more mutant genes
198
Risk of a multifactorial inheritance increases with what?
increases with the number of abnormal genes inherited
199
Normal phenotypic multifactoral characteristics include? 4
1. hair color
2. height
3. eye
4. skin color
200
in multifactorial inheritance, is the rate of recurrence the same for all the siblings?
YES 2-7%
201
Disorders/defects associated with multifactoral inheritance include? 7
cleft lip/palate, congenital heart disease, coronary heart disease, hypertension, gout, diabetes mellitus and pyloric stenosis
202
What is a karyotype?
An arrangement of chromosomes that is obtained from freshly obtained dividing cells such as leukocytes, fibroblasts, or amniocytes
203
Cytogenetic notation of normal female?
46,XX
204
Cytogenetic notation of female with down's?
47,XX +21
205
Cytogenetic notation of female with Turner's?
45,X
206
What does the notation mean (45,XX der(13,14)?
Designates a “derived” (der) chromosome formed from the fusion of the long arms of chromosomes 13 and 14 with loss of the short arm material from both chromosomes
207
A derived chromosome can only occur with what chromosomes?
The five acrocentric (minimal short arms) chromosomes: 13, 14, 15, 21, 22
208
What does 46,XX,del (5p) mean?
deletion of DNA from the short arm of chromosome
209
What does 46,XY t(9;22)(q34;q11) mean?
reciprocal translocation between chromosomes 9 and 22. This forms the abnormal BCR-ABL gene seen in chronic myelogenous leukemia. Also known as the Philadelphia chromosome
210
What does 46,XY inv(16), t(16;16) mean?
Designates an inversion translocation in which a segment of chromosome 16 DNA is reversed or inverted within the chromosome
211
A paracentric inversion involves the centromere, yes or no?
No
212
A pericentric inversion involves the centromere, yes or no?
Yes
213
Karyotyping involves looking at chromosomes when?
How is this accomplished?
What stain is used?
metaphase portion of mitosis
mitosis—use the drug colchicine to stop the mitotic cycle in metaphase
Giemsa
214
Can chromosomes be distinguished from each other in karyotyping? How?
Yes
| They have different banding patterns
215
What does q mean?
Long arm
216
What does p mean?
Short arm
217
Cytogenetic disorders are defined how?
Disorders that involve abnormal numbers or structures of chromosomes per classic karyotyping
218
What is diploid for humans?
46XX or 46XY (2N)
219
What is triploid for humans?
69XXX, etc, (3N)
220
What is aneuploid for humans?
Not Diploid or Polyploid (3N, 4N, etc.)
221
What is monosomy
| What is trisomy?
Loss of chromosome
| Gain of chromosome
222
FISH studies can be used to identify what?
Do you need dividing cells?
What must you know before starting?
specific DNA sequence in interphase nuclei as well as in karyotyping studies
no
specific DNA sequences to design the probes, which are labeled with a fluorescing compound
223
What is mosaicism?
presence of two or more populations of cells with different genotypes in a single individual
224
Examples of mosaicism? 3
1. normal cells and monosomy
2. normal cells and trisomy
3. normal cells with specific gene mutation
225
Monosomy and trisomy usually result from what?
nondisjunction of chromosomes during gametogenesis (meiosis)
226
Mosaicism results from what
errors in mitosis in the zygote
227
What are the 3 main trisomies?
| How common is each
21: Downs (most common)
18: Edwards
13: Patau (least common)
228
What is Edwards karyotype?
47, XY, +18
229
What are some common Edwards symptoms? 6
```
kidney malformations,
structural heart defects at birth
omphalocele
esophageal atresia
mental retardation
developmental delays
```
230
What is Patau karyotype?
47, XY, +13
231
What are some common Patau symptoms?
Mental retardation and motor disorder
Microcephaly
Polydactyly (extra digits)
232
What is the MOST common of the chromsomal disorders?
Trisomy 21
233
Down syndrome risk for child increases with what?
Increased maternal age
234
Most common cause of trisomy 21 is what?
meiotic nondisjunction; 47,XX or XY, +21 (95%)
235
Three causes of trisomy 21? 3
1. Meiotic nondisjunction
2. Robertsonian translocation
3. Mosaics
236
Clinical findings of down's include? 8
1. Flat facial profile
2. Oblique palpebral fissures
3. Epicanthic folds
4. Congenital heart disease (40%), especially endocardial cushion defects
5. Acute leukemia (10-20X increased risk)
6. GI atresia,
7. Alzheimer disease (in patients older than 40),
8. immunodeficiencies
237
what is the Lyon hypothesis of cytogenetic disorders invovling sex chromosomes?
Only one active X chromosome is needed and the other copy(ies) are inactivated and become Barr bodies.
238
Can you have mosaics with sex chromosome disorders?
yes, if different X chromosomes are inactivated in different tissues. Some maternal cells may have both X chromosomes active
239
How do placental mammals and marsupial mammals differ in terms of X chromosome disorders?
In placental mammals either X chromosome may be inactivated, but in marsupial mammals the paternal X chromosome is preferentially inactivated
240
Normaly, sex chromosome disorders cause what?
subtle, chronic problems relating to sexual development and fertility
241
The higher the number of X chromosomes, the greater the likelihood of what?
Mental retardation
242
What is Klinefelter's syndrome?
Male hypogonadism that occurs when there are two or more X chromosomes and at least one Y chromosome (needed for the male phenotype
243
What is the classic form of Klinefelter's?
47,XXY
244
What are some mosaic examples of Klinefelter's?
46,XY/47,XXY
| 49,XXXXY
245
Manifestations of klinefelter's? 10
1. Slightly low IQ,
2. increased risk of mental retardation with additional copies of the X chromosome
3. Atrophic testes,
4. hypospadias,
5. cryptorchidism,
6. infertility,
7. gynecomastia,
8. female distribution of fat and skeletal abnormalities
9. Increased breast cancer
10. autoimmune disorders
246
Full chromsomal monosomy of any sort will resort in what?
Spontaneous abortion
247
Trisomy X entails what?
Syndrome in which females have an extra X chromosome - 47 XXX - two Barr bodies in cells
248
Trisomy X patients are at risk for what? (3)
Developmental delays
Speech, language and learning disabilities
Tall stature and poor muscle tone
249
Most trisomy X patients have what symptoms?
Just mild effects and will never be diagnosed
250
XYY Males have what karyotype?
47,XYY or 48,XYYY
251
XYY males have what symptoms? (3)
1. tall
2. acne
3. antisocial behavior
252
Turner syndrome results from what?
complete or partial monosomy of the X chromosome
253
Turner syndrome is characterized primarily by what?
hypogonadism in phenotypic females
254
Turner syndrome clinical findings? (8)
```
Short stature
Coarctation of aorta
Edema
Cystic hygromas
Webbing of the neck
Broad (shield) chest with widely spaced nipples
Streak ovaries
Nevi
```
255
Main symptoms of Turner syndrome? (4)
Primary amenorrhea
Infantile genitalia
Hypothyroidism
Insulin resistance
256
Nonmedelian inheritance includes what types of disorders? 4
1. Triplet repeat
2. genomic imprinting
3. mitochondrial mutations
4. gonadal mosaicism
257
Triplet repeat mutations are caused by what?
Caused by long segments of repeating nucleotides
258
Genomic imprinting involves what?
preferential down regulation (turning off) of genes
259
What are premutations?
increased numbers of trinucleotide repeats, but not enough to meet characteristics of full mutation
260
What is a full mutation?
Additional triple repeats with full spectrum of phenotypic changes
261
What is anticipation?
Clinical features worsen with each successive generation as a result of amplification of trinucleotide repeats during oogenesis or spermatogenesis
262
What is Sherman's Paradox?
Risk of having the full mutation and increased phenotypic changes depends on the position of the individual in the pedigree
263
Triplet repeat mutations include? (4)
Fragile X syndrome
Myotonic dystrophy
Friedreich ataxia
Huntington disease
264
What makes Huntington's disease special from other triplet repeat disorders?
Gain of function mutation
265
CGG triplet in an UTR is what mutation?
Fragile X
266
GAA triplet in an intron is what mutation?
Friedreich ataxia
267
CAG triplet in an extron is what mutation?
Huntington's disease
268
Fragile X syndrome involves what gene?
FMR-1
269
Why is the disease called Fragile X syndrome?
the triple repeats give the X chromosome a “broken” appearance on G banding
270
How does Fragile X rate in terms of mental retardation diseases?
Second behind Downs
271
Characteristic phenotype of Fragile X? (3)
1. Long face with large mandible,
2. large, everted ears,
3. macroorchidism in 90% of post-pubertal males
272
What phenotype of a disease is similar to Fragile X's?
Marfan
273
Fragile site is seen where on the chromosome?
Xq27.3
274
At the fragile site, what is found?
CGG is the trinucleotide repeat
275
Normal CGC repeat at the fragile site?
29 or less
276
Premutation CGC repeat at fragile site?
50-200
277
Full mutation CGC repeat at fragile site?
250-4000
