18: Genetics in Relation to the Skin Flashcards
1
Q
What percentage of monogenic gene disorders with known molecular mechanisms have skin manifestations?
A
25% of monogenic gene disorders with known molecular mechanisms have skin manifestations.
2
Q
What are the key benefits of dissecting the human genome in dermatology?
A
The key benefits include:
- Documentation of new information about disease causation.
- Improving the accuracy of diagnosis and genetic counseling.
- Making DNA-based prenatal testing feasible.
3
Q
What is the composition of the human genome in terms of chromosomes?
A
The human genome consists of 46 chromosomes, which include:
- 22 pairs of autosomes (chromosome 22)
- 2 sex chromosomes (X and Y)
4
Q
What are telomeres and their function in cell division?
A
Telomeres are the ends of chromosomal arms consisting of multiple tandem repeats of short DNA sequences. They protect the chromosome ends and are shortened during each round of cell division, which helps determine the ‘age’ of somatic cells. When telomere length falls below a certain threshold, the cell undergoes senescence.
5
Q
What is the role of telomerase in relation to telomeres?
A
Telomerase is a protein-RNA enzyme complex that adds additional repeats to telomeres, counteracting the shortening that occurs during DNA replication in somatic cells.
6
Q
What are the structural features common to all human chromosomes?
A
All human chromosomes consist of two chromosomal arms, designated as ‘p’ and ‘q,’ and have telomeres at their ends, which consist of multiple tandem repeats of short DNA sequences.
7
Q
How can the ‘age’ of somatic cells be determined in terms of their division history?
A
The ‘age’ of somatic cells can be determined by measuring the length of their telomeres, as one telomere repeat is trimmed off during each round of cell division.
8
Q
What is the role of telomerase in telomere maintenance?
A
Telomerase is a protein–RNA enzyme complex that adds additional repeats to telomeres, maintaining their length.
9
Q
What percentage of inherited single-gene disorders have a skin phenotype?
A
About 25% of inherited single-gene disorders have a skin phenotype.
10
Q
What is the significance of cytogenetic chromosome bands like 17q21.2 in dermatology?
A
Cytogenetic chromosome bands like 17q21.2 help locate specific genes, such as type I keratin genes, which are relevant to skin conditions.
11
Q
How does the trimming of telomere repeats during cell division relate to cellular senescence?
A
When telomere length falls below a certain threshold due to trimming during cell division, the cell undergoes senescence.
12
Q
What is the role of telomerase in preventing cellular aging?
A
Telomerase adds repeats to telomeres, preventing their shortening and delaying cellular aging.
13
Q
What is the significance of the cytogenetic chromosome band 17q21.2 in dermatology?
A
The cytogenetic chromosome band 17q21.2 is significant because it is where type I keratin genes reside, which are important for skin structure and function.
14
Q
What is the difference between a polymorphism and a mutation in the human genome?
A
Polymorphisms are sequence dissimilarities within the normal population that have no relevance to disease or phenotypic traits, while mutations are changes in the nucleotide sequence that lead to changes in protein composition.
15
Q
What are polymorphisms and how do they relate to genetic variation in healthy individuals?
A
Polymorphisms are sequence dissimilarities within the genetic code of two healthy individuals that have no relevance to disease or phenotypic traits.
16
Q
What is a missense mutation and how does it differ from a nonsense mutation?
A
A missense mutation changes one amino acid to another, while a nonsense mutation leads to premature termination of translation, resulting in a truncated protein.
17
Q
What defines a silent mutation in the context of genetic mutations?
A
A silent mutation is a type of mutation that does not change the amino acid composition of a protein, despite a change in the nucleotide sequence.
18
Q
What biological function do telomeres contribute to, and why is this important?
A
Telomeres contribute to a biological clock function that removes somatic cells that have undergone too many rounds of replication, reducing the risk of tumorigenesis or other functional aberrations.
19
Q
What is the clinical relevance of silent mutations in the human genome?
A
Silent mutations do not change the amino acid composition and are generally clinically irrelevant.
20
Q
How do single nucleotide polymorphisms (SNPs) differ from other genetic variations?
A
SNPs are single base pair substitutions that occur approximately once every 250 base pairs and are often clinically irrelevant.
21
Q
What is the impact of a frameshift mutation caused by an insertion or deletion?
A
A frameshift mutation disrupts the normal reading frame of a gene, potentially altering the entire protein sequence.
22
Q
What is the significance of the promoter region in gene expression?
A
The promoter region determines whether a gene is actively transcribed in specific cells or tissues.
23
Q
What are the four main patterns of inheritance in Mendelian disorders?
A
- Autosomal dominant
- Autosomal recessive
- X-linked dominant
- X-linked recessive
24
Q
What is the risk of transmitting an autosomal dominant disorder from an affected parent to their offspring?
A
The risk of transmitting the disorder is 50% for each child, regardless of the number of previously affected or unaffected offspring.
25
How are males and females affected by autosomal dominant disorders?
Males and females are affected in approximately equal numbers, and the disorder can be transmitted from generation to generation.
26
What does the term 'semidominant' refer to in the context of autosomal dominant disorders?
The term 'semidominant' is applied when the phenotype in heterozygous individuals is less than that observed for homozygous subjects.
27
What is the risk of the next generation being affected for unaffected offspring of an individual with an autosomal dominant disorder?
The risk of the next generation being affected is negligible, provided that the partner does not have the autosomal dominant condition.
28
In autosomal dominant disorders, how are males and females affected, and what is the pattern of inheritance?
Males and females are affected in approximately equal numbers, and the disorder can be transmitted from generation to generation, with each affected individual having a 50% chance of passing the disorder to their offspring.
29
What is the inheritance pattern of autosomal recessive disorders and the risk of transmission to offspring?
In autosomal recessive disorders, both parents are carriers of one normal and one mutated allele. If both mutated alleles are transmitted to the offspring, the risk of developing the disorder is 25%.
30
How does X-linked dominant inheritance differ from autosomal dominant inheritance?
In X-linked dominant inheritance, both males and females are affected, and an affected male transmits the disorder to all his daughters and none of his sons.
31
In autosomal recessive disorders, what is the risk of offspring being affected if both parents are carriers?
The risk of offspring being affected is 25%.
32
What is the inheritance pattern in X-linked dominant disorders, and how does it differ from autosomal dominant inheritance?
In X-linked dominant disorders, an affected male transmits the disorder to all his daughters and none of his sons, unlike autosomal dominant inheritance.
33
Why might affected males in X-linked dominant disorders with cutaneous manifestations not survive?
Affected males may be aborted spontaneously or die before implantation, leading to the appearance of female-to-female transmission.
34
In autosomal recessive inheritance, what is the likelihood of a child being a carrier if both parents are carriers?
The likelihood of a child being a carrier is 50%.
35
What is the probability of a child being genotypically and phenotypically normal in autosomal recessive inheritance if both parents are carriers?
The probability is 25%.
36
How does the inheritance pattern of X-linked dominant disorders affect the offspring of an affected male?
An affected male transmits the disorder to all his daughters and none of his sons.
37
Why do X-linked dominant disorders often appear as female-to-female transmission?
This occurs because affected males may be aborted spontaneously or die before implantation.
38
What is the inheritance pattern of autosomal recessive disorders and what is the risk of an affected offspring if both parents are carriers?
In autosomal recessive disorders, both parents are carriers of one normal and one mutated allele. If both mutated alleles are transmitted to the offspring, the risk of an affected offspring is 25%. If one mutated and one wild-type allele is inherited, the child will be an unaffected carrier, and if both wild-type alleles are transmitted, the child will be genotypically and phenotypically normal.
39
How does X-linked dominant inheritance differ from autosomal dominant inheritance in terms of transmission to offspring?
In X-linked dominant inheritance, both males and females are affected, and an affected male transmits the disorder to all his daughters and none of his sons. This differs from autosomal dominant inheritance where both sexes can transmit the disorder to both sons and daughters.
40
What are the implications of X-linked dominant disorders with cutaneous manifestations for affected males?
In most X-linked dominant disorders with cutaneous manifestations, affected males may be aborted spontaneously or may die before implantation, which can lead to the appearance of female-to-female transmission in the pedigree.
41
What is the inheritance pattern of X-linked recessive conditions and how does it affect males and females differently?
X-linked recessive conditions occur almost exclusively in males. The gene is transmitted by carrier females who have the mutated gene on one X chromosome (heterozygous state). Sons of an affected male will be normal as they inherit their X chromosome from their unaffected mother. Daughters of an affected male will all be carriers since they inherit the affected X chromosome from their father.
42
In X-linked recessive conditions, why are males almost exclusively affected?
Males are almost exclusively affected because they have only one X chromosome, which, if carrying the mutation, will result in the condition.
43
What happens to the daughters of an affected male in X-linked recessive conditions?
All daughters of an affected male will be carriers, as they inherit the single X chromosome carrying the mutant gene from their father.
44
What is Lyonization, and how does it affect phenotypic expression in carrier females of X-linked recessive conditions?
Lyonization is the random inactivation of either the wild-type or mutated X chromosome in each cell during early gestation, leading to variable phenotypic expression in carrier females.
45
What is the genetic explanation for why sons of affected males in X-linked recessive conditions are unaffected?
Sons inherit their single X chromosome from their clinically unaffected mother, not their affected father.
46
How does Lyonization contribute to variability in X-linked recessive conditions among carrier females?
Lyonization randomly inactivates either the wild-type or mutated X chromosome in each cell, leading to variable phenotypic expression.
47
Why are males more frequently affected by X-linked recessive disorders than females?
Males have only one X chromosome, so a mutation on it will manifest, whereas females have a second X chromosome that can compensate.
48
What is the inheritance pattern of X-linked recessive conditions and how does it affect male and female offspring differently?
X-linked recessive conditions are transmitted by carrier females to their offspring. Males, who have only one X chromosome, are more likely to express the condition. The sons of an affected male will be normal since they inherit their X chromosome from their unaffected mother. In contrast, all daughters of an affected male will be carriers, having inherited the affected X chromosome from their father.
49
How does Lyonization explain the variability in phenotypic expression among carrier females of X-linked recessive conditions?
Lyonization is the random inactivation of one of the two X chromosomes in females, which can lead to variable phenotypic expression among carrier females.
50
What are the skin manifestations associated with Turner syndrome?
- Redundant neck skin and peripheral edema
- Cutis laxa (neck, buttocks)
- Hypoplastic, soft upturned nails
- Increased incidence of keloids
51
What are the general features of Klinefelter syndrome?
- No manifestations before puberty
- Small testes, poorly developed secondary sexual characteristics
- Infertility
- Tall, obese, osteoporosis
52
What skin manifestations are associated with 47 XXY?
- Severe acne
- Acrocyanosis
- Peripheral vascular disease
53
What are the general features of Fragile X syndrome?
- Mental retardation
- Mild dysmorphism
- Hyperextensible joints, flat feet
54
What skin manifestations can develop in individuals with 48 XXYY?
- Increased incidence of systemic lupus erythematosus
- Multiple cutaneous angiomatosis
55
What are the skin manifestations associated with Turner syndrome and their clinical significance?
Turner syndrome is characterized by skin manifestations such as:
- Redundant neck skin and peripheral edema
These features can indicate underlying lymphatic issues and may require monitoring for associated complications such as cardiovascular anomalies.
- Cutis laxa (loose skin on neck and buttocks)
This can lead to increased skin fragility and may necessitate dermatological care.
56
How does the skin phenotype differ between Klinefelter syndrome and 47 XYY syndrome?
The skin manifestations of Klinefelter syndrome and 47 XYY syndrome include:
| Syndrome | Skin Manifestations | Clinical Implications |
|----------|---------------------|----------------------|
| Klinefelter syndrome | May develop gynecomastia | Indicates hormonal imbalances; may require endocrinological evaluation |
| 47 XYY syndrome | Severe acne | May require dermatological treatment; can impact psychosocial well-being |
57
What are the general features and skin manifestations of 49 XXXXY syndrome?
49 XXXXY syndrome presents with:
- Slow mental and physical development
- Large, low-set, malformed ears
- Small genitalia
The skin manifestations include:
- Hypotrichosis (variable hair growth)
This can affect the individual's appearance and may require supportive care.
58
What is the most common numerical chromosomal abnormality and what does it involve?
Trisomy is the most common numerical chromosomal abnormality, which involves the presence of an extra chromosome.
59
What is uniparental disomy and what are its variants?
Uniparental disomy is the inheritance of both copies of a chromosome pair from just one parent. Its variants include:
1. Uniparental heterodisomy - presence of a part chromosome homologs.
2. Uniparental isodisomy - two identical copies of a single homolog.
60
What are the three phenotypic abnormalities associated with genomic imprinting?
The three phenotypic abnormalities associated with genomic imprinting are:
1. Intrauterine growth retardation
2. Developmental delay
3. Short stature
61
What is the definition of mosaicism in genetics?
Mosaicism refers to the presence of a mixed population of cells bearing different genetic or chromosomal characteristics, leading to phenotypic diversity.
62
What are the two types of segmental mosaicism for autosomal dominant disorders?
Segmental mosaicism for autosomal dominant disorders occurs in two ways:
1. Postzygotic mutation with the skin outside the segment and genomic DNA being normal.
2. Heterozygous genomic mutation in all cells that is exacerbated by loss of heterozygosity within a segment or along the line of Blaschko.
63
What is revertant mosaicism and how does it relate to genetic abnormalities?
Revertant mosaicism (Natural gene therapy) refers to the genetic correction of an abnormality through various phenomena, including:
- Back mutations
- Iatrogenic crossovers
- Mitotic gene conversion
- Second site mutations
This can involve genes such as keratin 14, collagen XVII, and others in different forms of epidermolysis bullosa (EB).
64
A patient presents with developmental delay, short stature, and intrauterine growth retardation. Genetic testing reveals uniparental disomy of chromosome 15. What are the two possible syndromes, and how do they differ?
The two possible syndromes are Prader-Willi syndrome and Angelman syndrome. Prader-Willi syndrome occurs when the paternal copy of chromosome 15 is missing or inactive, while Angelman syndrome occurs when the maternal copy is missing or inactive.
65
A patient has a mixed population of cells with different genetic characteristics, leading to phenotypic diversity. What is this condition called, and what are its two main types?
This condition is called mosaicism. The two main types are somatic mosaicism, where the mutation occurs after fertilization, and gonosomal mosaicism, which involves both gonads and somatic tissue.
66
A patient has a chromosomal abnormality involving the exchange of fragments between two chromosomes without any loss of DNA. What is this condition called?
This condition is called balanced translocation.
67
A patient has a mitochondrial disorder. What is the inheritance pattern, and how many genes are involved in the mitochondrial genome?
Mitochondrial disorders are inherited solely from the mother. The mitochondrial genome contains 37 genes: 13 encode respiratory chain complexes, 22 encode transfer RNA, and 2 encode ribosomal RNA.
68
What is revertant mosaicism, and in which conditions has it been observed?
Revertant mosaicism refers to the natural genetic correction of an abnormality through phenomena like back mutations or mitotic gene conversion. It has been observed in conditions such as epidermolysis bullosa (EB) and ichthyosis with confetti.
69
A patient has a loss of part of a chromosome, leading to X-linked ichthyosis. What is this chromosomal abnormality called?
This chromosomal abnormality is called deletion.
70
A patient has a mixture of two homologs of a chromosome. What is this condition called, and how does it differ from uniparental isodisomy?
This condition is called meroisodisomy. It differs from uniparental isodisomy, where two identical copies of a single homolog are inherited.
71
What are the three phenotypic abnormalities associated with genomic imprinting disorders?
The three phenotypic abnormalities are intrauterine growth retardation, developmental delay, and short stature.
72
A patient has a chromosomal abnormality with an extra chromosome. What is this condition called, and what is its most common form?
This condition is called trisomy, and its most common form is Down syndrome (trisomy 21).
73
What is the significance of the lines of Blaschko in genetic disorders?
The lines of Blaschko represent the lines of margination and proliferation of epidermal cells during embryogenesis. They are significant in segmental mosaicism and other genetic skin disorders.
74
What is heteroplasmy, and in which conditions is it observed?
Heteroplasmy is the presence of mixed mitochondrial DNA species within a cell. It is observed in both benign conditions like lipoma and malignant conditions like EMPD and Bowen disease.
75
What is the difference between uniparental heterodisomy and uniparental isodisomy?
Uniparental heterodisomy involves the presence of a pair of chromosome homologs from one parent, while uniparental isodisomy involves two identical copies of a single homolog from one parent.
76
A patient has a mutation in keratin 14 leading to epidermolysis bullosa. What natural phenomenon could potentially correct this mutation?
Revertant mosaicism, a natural gene therapy phenomenon, could potentially correct this mutation.
77
A patient has a chromosomal abnormality where both copies of a chromosome pair are inherited from one parent. What is this condition called?
This condition is called uniparental disomy.
78
What are the two main types of mosaicism, and how do they differ?
The two main types are somatic mosaicism, where the mutation occurs after fertilization, and gonosomal mosaicism, which involves both gonads and somatic tissue.
79
A patient has a chromosomal abnormality involving the exchange of fragments between two chromosomes. What is this condition called, and what are its two types?
This condition is called translocation. The two types are reciprocal translocation, where fragments are exchanged, and balanced translocation, where no DNA is lost.
80
A patient has a loss of a complete chromosome. What is this condition called, and which chromosome is commonly affected?
This condition is called monosomy, and it commonly affects the X chromosome.
81
What is the difference between somatic mosaicism and gonosomal mosaicism?
Somatic mosaicism involves mutations occurring after fertilization in somatic cells, while gonosomal mosaicism involves both gonads and somatic tissue.
82
What is the inheritance pattern of mitochondrial disorders, and how many genes are involved?
Mitochondrial disorders are maternally inherited and involve 37 genes.
83
What is the significance of the lines of Blaschko in genetic disorders?
The lines of Blaschko represent the embryonic development of skin cells and are significant in segmental mosaicism.
84
What is the difference between trisomy and monosomy?
Trisomy involves the presence of an extra chromosome, while monosomy involves the loss of a complete chromosome.
85
What is the difference between reciprocal and balanced translocation?
Reciprocal translocation involves the exchange of fragments between two chromosomes, while balanced translocation involves no loss of DNA during the exchange.
86
What is the significance of revertant mosaicism in genetic disorders?
Revertant mosaicism represents a natural correction of genetic abnormalities and has been observed in conditions like epidermolysis bullosa.
87
What are the implications of uniparental disomy in terms of phenotypic abnormalities, and how does it relate to genomic imprinting?
Uniparental disomy can lead to distinct phenotypes due to genomic imprinting, where only one parent's alleles are expressed. The three phenotypic abnormalities associated with this condition include:
1. Intrauterine growth retardation
2. Developmental delay
3. Short stature
88
How does somatic mosaicism differ from gonosomal mosaicism in terms of genetic implications and tissue involvement?
Somatic mosaicism involves a single gene mutation that occurs after fertilization, affecting somatic cells. In contrast, gonosomal mosaicism involves mutations in both gonadal and somatic tissues, with the potential for the mutation to be passed on to offspring if it occurs in the gonads.
89
What are the two ways segmental mosaicism can occur for autosomal dominant disorders, and what are the clinical implications of each?
Segmental mosaicism for autosomal dominant disorders can occur in two ways:
1. Postzygotic mutation: This results in a mutation occurring after fertilization, leading to a segment of skin with the mutation while the genomic DNA outside remains normal.
2. Heterozygous genomic mutation: This occurs in all cells but is exacerbated by loss of heterozygosity within a segment or along the lines of Blaschko, potentially leading to a patchy distribution of the disorder.
The clinical implications include variable expressivity and the potential for different phenotypic presentations in affected individuals.
90
What is the significance of revertant mosaicism in genetic therapy, and what are some examples of conditions it may address?
Revertant mosaicism refers to the genetic correction of an abnormality through various mechanisms, such as back mutations or mitotic gene conversion. This phenomenon can lead to a partial restoration of normal function in affected tissues. Examples of conditions it may address include:
- Epidermolysis Bullosa (EB): Keratin 14, collagen XVII, collagen VII
- Ichthyosis with confetti: Keratin 10
These examples highlight the potential for revertant mosaicism to improve clinical outcomes in genetic disorders.
91
What are the classic loci of HLA class I and class II?
HLA class I:
- HLA-A
- HLA-B
- HLA-Cw
HLA class II:
- HLA-DR
- HLA-DQ
- HLA-DP
- HLA-DM
- HLA-DO
92
What are the two components of mammalian DNA methylation machinery?
1. DNA methyltransferase - establishes and maintains genome-wide DNA methylation patterns.
2. Methyl-CpG-binding proteins - involved in scanning and interpreting the methylation patterns.
93
What are the key components of genetic counseling?
- Interpretation of family and medical histories to assess the chance of disease occurrence or recurrence.
- Education about inheritance, testing, management, prevention, resources, and research.
- Counseling to promote informed choice and adaptation to the risk or condition.
94
What are the appropriate weeks of gestation for fetal skin biopsies for different conditions?
| Condition | Weeks AOG |
|----------------|------------|
| Epidermolysis Bullosa (EB) | 16 weeks |
| Ichthyosis | 20-22 weeks |
| Amniotic fluid | 16 weeks |
| Chorionic villi | 10-12 weeks |
95
What are the two approaches to gene therapy?
1. In vivo approach - the gene therapy agent is delivered directly to the patient’s skin or another tissue.
2. Ex vivo approach - a skin biopsy is taken, keratinocytes or fibroblasts are expanded in culture, treated with the gene therapy agent, and then grafted onto or injected back into the patient.
96
A fetus is suspected of having epidermolysis bullosa (EB). What prenatal diagnostic method and timing would you recommend?
For epidermolysis bullosa (EB), a fetal skin biopsy is recommended at 16 weeks of gestational age (AOG).
97
Explain the difference between in vivo and ex vivo gene therapy approaches.
In vivo gene therapy involves delivering the gene therapy agent directly to the patient’s skin or tissue. Ex vivo gene therapy involves taking a skin biopsy, expanding keratinocytes or fibroblasts in culture, treating them with the gene therapy agent, and then grafting or injecting them back into the patient.
98
What are the two components of mammalian DNA methylation machinery, and what are their roles?
The two components are DNA methyltransferase, which establishes and maintains genome-wide DNA methylation patterns, and methyl-CpG-binding proteins, which scan and interpret the methylation patterns.
99
What are the classic loci of HLA class I and class II regions?
The classic loci of HLA class I are HLA-A, HLA-B, and HLA-Cw. The classic loci of HLA class II are HLA-DR, HLA-DQ, HLA-DP, HLA-DM, and HLA-DO.
100
What is the role of genetic counseling, and what are its three main components?
The role of genetic counseling is to help patients and families understand the risks of recurrence or transmission of a condition. Its three main components are interpretation of family and medical histories, education about inheritance and testing, and counseling to promote informed choice and adaptation.
101
A patient has a dominant-negative genetic disorder. What type of gene therapy would be most appropriate?
Gene inhibition therapy would be most appropriate for treating dominant-negative genetic disorders.
102
What are the two main approaches to gene therapy, and how do they differ?
The two main approaches are in vivo and ex vivo. In vivo involves direct delivery of the gene therapy agent to the patient, while ex vivo involves treating cells outside the body and then reintroducing them.
103
What is the role of DNA methyltransferase in epigenetics?
DNA methyltransferase establishes and maintains genome-wide DNA methylation patterns, which are crucial for regulating gene expression.
104
What is the significance of the HLA region in disease association?
The HLA region, located on the short arm of chromosome 6 at 6p21, is crucial for immune response and is associated with various diseases.
105
What are the two main components of mammalian DNA methylation machinery?
The two main components are DNA methyltransferase and methyl-CpG-binding proteins.
106
What is the role of methyl-CpG-binding proteins in epigenetics?
Methyl-CpG-binding proteins are involved in scanning and interpreting DNA methylation patterns.
107
What is the role of genetic counseling in prenatal diagnosis?
Genetic counseling helps interpret family and medical histories, educate about inheritance and testing, and promote informed decision-making in prenatal diagnosis.
108
What are the two main approaches to gene therapy?
The two main approaches are in vivo, where the therapy is delivered directly to the patient, and ex vivo, where cells are treated outside the body and reintroduced.
109
What is the role of epigenomics in genetic research?
Epigenomics involves analyzing changes in DNA methylation and other epigenetic processes to understand gene regulation and disease mechanisms.
110
What is the role of HLA class I and class II loci in the immune system?
HLA class I loci (HLA-A, HLA-B, HLA-Cw) present antigens to cytotoxic T cells, while HLA class II loci (HLA-DR, HLA-DQ, HLA-DP) present antigens to helper T cells.
111
What are the classic loci of HLA class I and class II in the Histocompatibility Antigen Disease Association?
HLA class I:
- HLA-A
- HLA-B
- HLA-Cw
HLA class II:
- HLA-DR
- HLA-DQ
- HLA-DP
- HLA-DM
- HLA-DO
112
What are the two main components of mammalian DNA methylation machinery in epigenetics?
1. DNA methyltransferase: Establishes and maintains genome-wide DNA methylation patterns.
113
What are the classic loci of HLA class I?
HLA-A, HLA-B, HLA-Cw
114
What are the classic loci of HLA class II?
HLA-DR, HLA-DQ, HLA-DP, HLA-DM, HLA-DO
115
What are the two main components of mammalian DNA methylation machinery in epigenetics?
1. DNA methyltransferase: Establishes and maintains genome-wide DNA methylation patterns.
2. Methyl-CpG-binding proteins: Involved in scanning and interpreting the methylation patterns.
116
What key components should be included in genetic counseling?
- Interpretation of family and medical histories to assess disease occurrence or recurrence.
- Education about inheritance, testing, management, prevention, resources, and research.
- Counseling to promote informed choice and adaptation to the risk or condition.
117
What are the appropriate gestational ages for fetal skin biopsies in prenatal diagnosis for Epidermolysis Bullosa (EB)?
16 weeks AOG
118
What are the appropriate gestational ages for fetal skin biopsies in prenatal diagnosis for Ichthyosis?
20-22 weeks AOG
119
What are the two approaches to gene therapy?
1. In vivo approach: The gene therapy agent is delivered directly to the patient’s skin or another tissue.
2. Ex vivo approach: A skin biopsy is taken, keratinocytes or fibroblasts are expanded in culture, treated with the gene therapy agent, and then grafted onto or injected back into the patient.
