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What is the approximate size of the mitochondrial genome?
What is the approximate size of the mitochondrial genome?
What is the characteristic of mitochondrial DNA inheritance in humans?
What is the characteristic of mitochondrial DNA inheritance in humans?
What is the term for the presence of a single type of mitochondrial DNA molecule within an individual?
What is the term for the presence of a single type of mitochondrial DNA molecule within an individual?
What is a characteristic of diseases resulting from mitochondrial DNA mutations?
What is a characteristic of diseases resulting from mitochondrial DNA mutations?
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How many genes are encoded in the mitochondrial genome?
How many genes are encoded in the mitochondrial genome?
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What is a feature of the mitochondrial genome that differs from the nuclear genome?
What is a feature of the mitochondrial genome that differs from the nuclear genome?
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What is the main factor that determines the pattern of single-gene disorders in pedigrees?
What is the main factor that determines the pattern of single-gene disorders in pedigrees?
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What is the characteristic of males in relation to X-linked genes?
What is the characteristic of males in relation to X-linked genes?
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What is the difference between autosomal and X-linked disorders in terms of clinical expression?
What is the difference between autosomal and X-linked disorders in terms of clinical expression?
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What is the characteristic of mitochondrial inheritance?
What is the characteristic of mitochondrial inheritance?
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What is the term for the phenomenon where a single gene has multiple effects on the phenotype?
What is the term for the phenomenon where a single gene has multiple effects on the phenotype?
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What is the term for the mixture of different mitochondrial DNA types within a cell?
What is the term for the mixture of different mitochondrial DNA types within a cell?
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What is the characteristic of X-linked recessive disorders in females?
What is the characteristic of X-linked recessive disorders in females?
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What is the term for a female carrier of a recessive X-linked allele who has phenotypic expression of the disease?
What is the term for a female carrier of a recessive X-linked allele who has phenotypic expression of the disease?
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What is the pattern of inheritance of X-linked recessive disorders?
What is the pattern of inheritance of X-linked recessive disorders?
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Why is it unusual for a female to be homozygous for an X-linked recessive disorder?
Why is it unusual for a female to be homozygous for an X-linked recessive disorder?
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What is the characteristic of muscle from DMD carriers?
What is the characteristic of muscle from DMD carriers?
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What is the difference between X-linked dominant and recessive inheritance patterns?
What is the difference between X-linked dominant and recessive inheritance patterns?
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What is a characteristic of X-linked recessive inheritance patterns?
What is a characteristic of X-linked recessive inheritance patterns?
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What happens to the daughters of an affected male in X-linked recessive inheritance?
What happens to the daughters of an affected male in X-linked recessive inheritance?
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What is a key feature of X-linked dominant inheritance?
What is a key feature of X-linked dominant inheritance?
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What can be observed in a pedigree demonstrating X-linked dominant inheritance?
What can be observed in a pedigree demonstrating X-linked dominant inheritance?
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Why are isolated cases of X-linked recessive disorders often due to new mutations?
Why are isolated cases of X-linked recessive disorders often due to new mutations?
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What is the term for the expression of a condition in heterozygotes?
What is the term for the expression of a condition in heterozygotes?
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What is a characteristic of X-linked recessive disorders?
What is a characteristic of X-linked recessive disorders?
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Study Notes
Patterns of Single-Gene Inheritance
- Four basic patterns of single-gene inheritance depend on whether the phenotype is dominant or recessive and the chromosomal location of the gene locus (autosome or sex chromosome)
X-Linked Inheritance
- X-linked disorders affect males more severely than females due to hemizygosity in males and heterozygosity in females
- Females can be heterozygous or homozygous at X-linked loci, while males are never heterozygous for alleles at X-linked loci
- X inactivation leads to random inactivation of one X chromosome in females, affecting expression of X-linked genes
Mitochondrial Genome
- Mitochondrial DNA (mtDNA) is a circular chromosome located inside mitochondrial organelles, not in the nucleus
- mtDNA contains 37 genes encoding 13 polypeptides, 2 types of ribosomal RNA, and 22 transfer RNAs
- Rearrangements and point mutations in mtDNA can cause human disease, often involving the central nervous and musculoskeletal systems
- Mitochondrial genome has three unusual features: replicative segregation, homoplasmy and heteroplasmy, and maternal inheritance
Maternal Inheritance of mtDNA
- mtDNA is inherited solely from the mother due to elimination of sperm mitochondria from the embryo
- All children of a female with a mtDNA mutation will inherit the mutation, while none of the offspring of a male carrying the same mutation will inherit it
Expression of X-Linked Genes
- Recessive and dominant patterns of X-linked inheritance are distinguished based on the phenotype in heterozygous females
- X-linked "dominant" and "recessive" patterns depend on the expression of the phenotype in carriers
X-Linked Recessive Inheritance
- X-linked recessive disorders are typically expressed in all males who receive the mutated allele and only in females who are homozygous for the mutation
- X-linked recessive disorders are generally restricted to males and rarely seen among females
- Hemophilia A is a classic X-linked recessive disorder
Manifesting Heterozygotes and Unbalanced Inactivation
- Female carriers of X-linked recessive alleles may occasionally express the disease, known as manifesting heterozygotes
- Manifesting heterozygotes have been described for many X-linked recessive disorders, including color blindness and hemophilia A
Characteristics of X-Linked Recessive Inheritance
- Incidence of the trait is higher in males than females
- Heterozygous females are usually unaffected, but some may express the condition with variable severity
- The gene responsible is transmitted from an affected man through all his daughters
- Any of his daughters' sons has a 50% chance of inheriting it
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Description
This quiz covers advanced topics in single-gene inheritance, including X-linked inheritance, dosage compensation, and pseudoautosomal inheritance. It also explores mosaicism, unstable repeat expansions, and mitochondrial genome mutations.
