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Questions and Answers
What is the minimum number of mutated copies of a gene required for an autosomal dominant disorder to occur?
What is the probability of passing an autosomal dominant defect to an offspring if one parent is affected?
What type of inheritance pattern is characterized by the requirement of two mutated copies of the gene for the disease to occur?
What is the term for the phenomenon where a mutated gene is not always expressed, even if an individual has inherited it?
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Which type of mutation is not passed onto succeeding generations?
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What is the term for a gene that has identical versions inherited from both parents?
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Which of the following disorders is an example of an autosomal recessive disorder?
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What is the chance of an offspring inheriting an autosomal recessive disorder if both parents are carriers?
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What is the primary consequence of inherited defects in genes encoding enzymes involved in metabolic pathways?
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What percentage of inborn errors of metabolism present between birth and one year of age?
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What is the primary approach to treating inborn errors of metabolism?
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What is the estimated number of diseases with a genetic basis?
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What is the consequence of genetic disorders of the body's biochemistry?
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What percentage of inborn errors of metabolism present in adulthood?
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What is the underlying cause of genetic deficiencies in the production of enzymes, receptor proteins, and other macromolecules?
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Which of the following is NOT a type of macromolecule affected by genetic disorders?
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What is the name of the disease caused by a deficiency of the enzyme homogentisic acid oxidase?
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Which of the following is a characteristic of phenylketonuria?
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Who is credited with the discovery that human genetic diseases are a consequence of enzyme deficiencies?
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What is the result of the deficiency of the enzyme homogentisic acid oxidase in Alkaptonuria?
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Which of the following is an example of a CHO disorder?
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What is the name of the enzyme deficient in Phenylketonuria?
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Study Notes
Inborn Errors of Metabolism
- Genetic disorders affecting the body's biochemistry, causing disease and death
- 3000 diseases have a genetic basis, including chronic diseases, cancer, and inborn errors of metabolism
Characteristics of Inborn Errors of Metabolism
- Present early in life (80% before age 1)
- No cure, limited treatment, except for dietary modification
- Genetic deficiencies in enzyme production, transport proteins, receptor proteins, and subcellular organelles
Types of Inborn Errors of Metabolism
- CHO disorders: galactose, glucose, glycogen, fructose
- Protein disorders: amino acid, organic acid, urea cycle, haemoglobin, connective tissue
- Lipid disorders: synthesis, degradation, storage, transport
- Nucleic acids disorders: purines, pyrimidines
History of Inborn Errors of Metabolism
- Archibald Garrod (1902): human genetic diseases are a consequence of enzyme deficiencies
- Helped elucidate many metabolic pathways
Examples of Inborn Errors of Metabolism
- Alkaptonuria: lack of homogentisic acid oxidase, urine turns black, arthritis in later life
- Phenylketonuria: accumulation of phenylpyruvate in urine due to phenylalanine hydroxylase deficiency
Human Genetic Make-up
- Genes are arranged on chromosomes (23 pairs, 22 autosomes, XX or XY sex chromosomes)
- Most cells are diploid, germ cells are also diploid, precursors of haploid gametes
Patterns of Inheritance
- Mendelian inheritance: new mutations in germ cells are passed onto succeeding generations
- Different patterns of inheritance: autosomal recessive, autosomal dominant, X-linked recessive, X-linked dominant, codominant
Autosomal Dominant Disorders
- One mutated copy causes disease
- Only one affected parent
- Males and females equally affected
- 50% chance of passing the defect
- Examples: Huntington's chorea, tuberous sclerosis, familial hypercholesterolaemia
Autosomal Recessive Disorders
- Two mutated copies of the gene are present in each cell
- Carrier parents
- Both sexes equally affected
- 25% chance
- Examples: alkaptonuria, cystic fibrosis, Tay-Sachs disease, Friedreich's ataxia, phenylketonuria
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Description
This quiz covers the relationship between genetic defects and metabolic diseases, specifically diabetes mellitus. It explores the role of enzymes and genes in metabolic pathways and how inherited defects can lead to disease.
