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Category Archives: Genetics
Gonadal Mosaism
Gonadal Mosaism
What is the cause of gonadal mosaism?
Results from de novo mutation in the cells destined to form the gonads. (ie. the new mutation is confined to the gametes.)
Eg. phenotypically normal parents with several children who have osteogenesis imperfecta.
Genomic Imprinting
Genomic Imprinting
Difference between maternal and paternal imprinting?
Maternal imprinting results in transcriptional silencing whereas paternal imprinting results in inactivation of the gene.
Methylation is involved in inactivation.
Inheritance pattern in genomic imprinting, epigenetic, syndromes:
In Prader-Willi syndrome there is a deletion in the paternal chromosome 15. Maternal transcriptional silencing occurs at this same region.
Since there is already imprinting of the maternal gene (transcriptional silencing) the last only remaining copy of the gene is no longer functional.
The opposite is true in Angelman syndrome.
Note the Angelman and Prader-Willi gene are in close approximation on chromosome 15.
Posted in Genetics
Tagged , Angelman syndrome, DNA methylation, Epigenetic diseases, Epigenetics, Genetic imprint, Genomic imprinting, Imprinting, Maternal imprinting, Paternal imprinting, Prader-Willi syndrome, Transcriptional silencing
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Mitochondrial Gene Mutations
Mitochondrial Gene Mutations
MUTATIONS IN MITOCHONDRIAL GENES
How are these mutations transmitted?
- mitochondrial DNA, mtDNA, is transferred from the mother by meiosis
What genes are involved?
- genes encoding enzymes involved in oxidative phosphorylation, such as in Leber hereditary optic neuropathy
Posted in Genetics
Tagged Leber hereditary optic neuropathy, Mitochondrial Gene Mutations, Mitochondrial genes, Mitochondrial mutations, Oxidative phosphorylation
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Non-Mendelian Inheritance
Non-Mendelian Inheritance
Different types of non-Mendelian inheritance:
1 Trinucleotide expansions
2. Mitochondrial mutations
3. Imprinting
4. Gonadal mosaism
Posted in Genetics
Tagged , Epigenetics, Genetic imprinting, Gonadal mosaism, Imprinting, Mitochondrial mutations, Non-mendelian, Non-Mendelian Inheritance, Trinucleotide expansions
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Trinucleotide repeat expansion diseases
Trinucleotide repeat expansion diseases:
1. Fragile X syndrome
2. Huntington
3. Friedrich ataxia
Posted in Genetics
Tagged , Fragile X Syndrome, Friedrich ataxia, Huntington disease, Trinucleotide repeat expansion
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Cytogenetics
Cytogenetics
Causes of aneuploidy:
1. Non-dysjunction
2. Anaphase lag
3. Mosaism
4. Translocation
Types of chromosomal rearrangments:
1. Translocation (balanced and Robertsonian)
2. Isochromosome
3. Inversion (pericentric, paracentric)
4. Ring chromosome
5. Deletion
Posted in Genetics
Tagged , Anaphase lag, Aneuploidy causes, Causes of aneuploidy, Chromosomal rearrangments, Chromosome rearrangement, Cytogenetic, Cytogenetics, Deletion, Inversion, Isochromosome, Mosaism, Non-dysjunction, Ring chromosome, translocation
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Glycogen Storage Diseases
Glycogen Storage Diseases
Glycogenoses, Glycogenosis
Types of Glycogen Storage Diseases:
- Hepatic (von Gierke)
- Myopathic (McArdle)
- Generalized (Pompe)
- cardiomegaly, hypotonia, HM, die in infancy
Posted in Genetics
Tagged , Glycogen storage, Glycogen storage disease, Glycogen Storage Diseases, Glycogenoses, Glycogenosis
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Mucopolysaccharidosis
Mucopolysaccharidosis
Mucopolysaccharidosis diseases (MPS)
- deficiency in enzymes that degrade GAG (heparin sulfate, keratin sulfate, dermatin sulfate, chondroitin sulfate)
“H and S”
- phagocytic cells
- Hunter and Hurler syndromes (iduronidase)
- Hepatosplenomegaly
- Skeletal deformities (coarse facies)
- Subendothelial deposits (especially coronaries)
Posted in Genetics
Tagged , Coarse facies, Enzyme deficiency, Hepatosplenomegaly, Hunter syndrome, Hurler syndrome, Iduronidase, MPS, Mucopolysaccharide, Mucopolysaccharidosis, Mucopolysacchidoses, Subendothelial deposit
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Lysosomal Storage Diseases
Lysosomal Storage Diseases
Tay Sachs Disease
A Sphingolipidosis
- gangliosidase
- gangliosides
- ganglion cells
- GM2
- hexoaminidase A
- accumulation of GM2 gangliosides in lysosomes
- whorled vacuoles in neurons and ganglion cells in retina → cherry red spot on macule
- fat stains (oil red O and Sudan black)
- die by the age of 3
Niemann Pick Disease
- spingomyelinase deficiency
- distention of lysosomal vacuoles with sphingomyelin in liver, brain, spleen (stored in neurons and in phagocytic cells)
- HSM
- gyri thinned, sulci widened → mental retardation
- die within 1-2 years of age
Niemann Pick Disease Summary:
- cell membranes
- sphingomyelinase
- sphingomyelin
- phagocytic cells
- vacuoles
- fat stains (oil red O and Sudan black)
- gyri, sulci
Gaucher’s Disease
Gaucher’s Disease is the most common lysosomal storage disease
- most common lysosomal storage disease
- Glucocerebrosidase mutation
- Glucocerebroside
- Phagocytic cells (spleen, liver, bone marrow, lymph nodes, thymus, peyer patches) affected
- characteristic big spleen due to accumulation of defective phagocytic cells
- Gaucher cells (crumpled tissue paper)
Posted in Genetics
Tagged , Gaucher cell, Gaucher cells, Gaucher’s Disease, Lysosomal storage, Lysosomal storage disease, Lysosomal storage diseases, Niemann Pick, Niemann-Pick disease, Storage disease, Storage diseases, Tay Sachs, Tay Sachs Disease
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Types of Mutations
Genetic Mutations
Types of mutations
· Point mutations (substitution), deletion, insertion, frameshift mutation
· Trinucleotide repeat expansion (eg. fragile X syndrome is an expansion of the FMR1 gene)
· Mutations to non-coding sequence of DNA (eg. to binding sites of transcription factors)
Posted in Genetics
Tagged , Deletion mutation, Frameshift mutation, Gene mutations, Genetic mutations, Insertion mutation, mutations, Point mutations, Trinucleotide repeat expansion, Types of genetic mutations, Types of mutations
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