2019最新单基因遗传病高级遗传英语
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4. The parents of the affected person may in some cases be consanguineous. This is especially likely if the mutant gene is rare in the population.
Autosomal Recessive Inheritance (AR)
• Chromosomal
Chromosomal imbalance causes alteration in gene dosage
• Mitochondrial
• Somatic mutations (cancer)
+ environment
Male
Dominant
Heterozygotes with one copy of the altered gene are affected
Characteristics of X-linked Dominant Inheritance
1. The incidence of the trait is much higher in females than in males (about twice) ,but affected females typically have milder (variable) expression of the phenotype.
inherited (translocations).
Single gene disorders:
disorders in which inheritance is due to a single mutant gene 1. Mendelian inheritance 2. Genes are units of heredity, based in DNA 3. Phenotype (physical or functional abnormalities)
2. both sexes are affected with equal frequency at a ratio of 1:1
3. Parents of an affected child are asymptomatic carriers of mutant alleles. heterozygous parents have a risk of 25% of affected offspring
X-linked Recessive males through carrier women, males affected almost exclusively, females affected only when affected father and carrier mother or with skewed X-inactivation
5. Dominant vs Recessive , based on phenotypic expression
Single gene disorders
- High risks to relatives - Dominant/recessive pedigree patterns - Some isolated cases due to new dominant mutations - Structural proteins, enzymes, receptors, transcription factors
Y-linked males affected
Characteristics of Autosomal Dominant inheritance
1. The phenotype usually appears in every generation, each affected person having an affected parent
单基因遗传病
Single gene disorders Monogenic disorders
ClaΒιβλιοθήκη Baidusification of Genetic Disorders
Etiology of diseases. For any condition the overall balance of genetic and environmental determinants can be represented by a point somewhere within the triangle.
Male
Recessive Homozygotes with two copies of the altered gene are affected
X-linked recessive Males with one copy of the altered gene on the X-chromosome are affected
Genotype (DNA change) 4. Autosomal vs X-linked
determined by whether the responsible gene is carried on one of the autosomal chromosomes or on the X chromosome
Genetic disorders
• Multifactorial (common)
- “Environmental” influences act on a genetic predisposition to produce a liability to a disease.
- One or more organ system affected. - Person affected if liability above a threshold.
4.The pedigree pattern is the same as autosomal dominant inheritance.
X-linked Dominant Inheritance (XD)
Characteristics of X-Linked
Recessive Inheritance
Single gene disorders are caused by defects in one particular gene, and often have simple and predictable inheritance patterns. They affect about 1 per cent of the population as a whole.
Exceptions : (1)fresh mutation (2)the disorder is not expressed or is expressed only subtly in a person who has inherited the responsible gene.
2. Any child of an affected parent has a 50 percent risk of inheriting the trait
Ⅰ 1 2
Ⅱ
1
23
Ⅲ4 1
I:1
I:2
II:1
II:2
II:3
II:5
II:6
II:8
III:1
III:2
IV:1
Characteristics of single gene inheritance
Autosomal Dominant vertical (successive), risk of affected offspring 50% (both sex)
Classification of genetic disorders
• Multifactorial
Variants in genes causing alteration of function
• Single gene
Mutations in single genes (often causing loss of function
3. both males and females are affected in a 1 : 1 ratio
Autosomal dominance inheritance (AD)
Pedigree showing typical inheritance of a form of progressive sensorineural deafness (DFNA1) inherited as an autosomal dominant trait
1. The incidence of the trait is much higher in males than in females.
2. The gene is ordinarily never transmitted directly from father to son (male-to-male), but it is transmitted by an affected male to all his daughters .
• Single gene (1% liveborn)
- Dominant/recessive pedigree patterns (Mendelian inheritance). - Can affect structural proteins, enzymes, receptors, transcription factors.
Characteristics of Autosomal Recessive Inheritance
1. An autosomal Recessive phenotype, typically is seen only in the sibship of the proband, not in parents, offspring, or other relatives.
2. Affected males with normal mates have normal sons and Affected daughters.
3. Both male and female offspring of Affected female have a 50 percent risk of inheriting the phenotype.
• Chromosomal (0.6% liveborn)
- Thousands of genes may be involved. - Multiple organ systems affected at multiple stages in gestation. - Usually de novo (trisomies, deletions, duplications) but can be
Autosomal Recessive horizontal, multiple sibs affected, usually one generation, consanguinity (+) risk of affected offspring 25%, carrier 50%
X-linked Dominant daughters of affected males (+), sons of affected males (-), affected females transmit the disorder to offspring of both sexes, risk of affected offspring 50%, but twice as many affected females as affected males (no male to male)
3. A carrier Female for an X-chromosomal mutation has a risk of 50% For an affected son.
Autosomal Recessive Inheritance (AR)
• Chromosomal
Chromosomal imbalance causes alteration in gene dosage
• Mitochondrial
• Somatic mutations (cancer)
+ environment
Male
Dominant
Heterozygotes with one copy of the altered gene are affected
Characteristics of X-linked Dominant Inheritance
1. The incidence of the trait is much higher in females than in males (about twice) ,but affected females typically have milder (variable) expression of the phenotype.
inherited (translocations).
Single gene disorders:
disorders in which inheritance is due to a single mutant gene 1. Mendelian inheritance 2. Genes are units of heredity, based in DNA 3. Phenotype (physical or functional abnormalities)
2. both sexes are affected with equal frequency at a ratio of 1:1
3. Parents of an affected child are asymptomatic carriers of mutant alleles. heterozygous parents have a risk of 25% of affected offspring
X-linked Recessive males through carrier women, males affected almost exclusively, females affected only when affected father and carrier mother or with skewed X-inactivation
5. Dominant vs Recessive , based on phenotypic expression
Single gene disorders
- High risks to relatives - Dominant/recessive pedigree patterns - Some isolated cases due to new dominant mutations - Structural proteins, enzymes, receptors, transcription factors
Y-linked males affected
Characteristics of Autosomal Dominant inheritance
1. The phenotype usually appears in every generation, each affected person having an affected parent
单基因遗传病
Single gene disorders Monogenic disorders
ClaΒιβλιοθήκη Baidusification of Genetic Disorders
Etiology of diseases. For any condition the overall balance of genetic and environmental determinants can be represented by a point somewhere within the triangle.
Male
Recessive Homozygotes with two copies of the altered gene are affected
X-linked recessive Males with one copy of the altered gene on the X-chromosome are affected
Genotype (DNA change) 4. Autosomal vs X-linked
determined by whether the responsible gene is carried on one of the autosomal chromosomes or on the X chromosome
Genetic disorders
• Multifactorial (common)
- “Environmental” influences act on a genetic predisposition to produce a liability to a disease.
- One or more organ system affected. - Person affected if liability above a threshold.
4.The pedigree pattern is the same as autosomal dominant inheritance.
X-linked Dominant Inheritance (XD)
Characteristics of X-Linked
Recessive Inheritance
Single gene disorders are caused by defects in one particular gene, and often have simple and predictable inheritance patterns. They affect about 1 per cent of the population as a whole.
Exceptions : (1)fresh mutation (2)the disorder is not expressed or is expressed only subtly in a person who has inherited the responsible gene.
2. Any child of an affected parent has a 50 percent risk of inheriting the trait
Ⅰ 1 2
Ⅱ
1
23
Ⅲ4 1
I:1
I:2
II:1
II:2
II:3
II:5
II:6
II:8
III:1
III:2
IV:1
Characteristics of single gene inheritance
Autosomal Dominant vertical (successive), risk of affected offspring 50% (both sex)
Classification of genetic disorders
• Multifactorial
Variants in genes causing alteration of function
• Single gene
Mutations in single genes (often causing loss of function
3. both males and females are affected in a 1 : 1 ratio
Autosomal dominance inheritance (AD)
Pedigree showing typical inheritance of a form of progressive sensorineural deafness (DFNA1) inherited as an autosomal dominant trait
1. The incidence of the trait is much higher in males than in females.
2. The gene is ordinarily never transmitted directly from father to son (male-to-male), but it is transmitted by an affected male to all his daughters .
• Single gene (1% liveborn)
- Dominant/recessive pedigree patterns (Mendelian inheritance). - Can affect structural proteins, enzymes, receptors, transcription factors.
Characteristics of Autosomal Recessive Inheritance
1. An autosomal Recessive phenotype, typically is seen only in the sibship of the proband, not in parents, offspring, or other relatives.
2. Affected males with normal mates have normal sons and Affected daughters.
3. Both male and female offspring of Affected female have a 50 percent risk of inheriting the phenotype.
• Chromosomal (0.6% liveborn)
- Thousands of genes may be involved. - Multiple organ systems affected at multiple stages in gestation. - Usually de novo (trisomies, deletions, duplications) but can be
Autosomal Recessive horizontal, multiple sibs affected, usually one generation, consanguinity (+) risk of affected offspring 25%, carrier 50%
X-linked Dominant daughters of affected males (+), sons of affected males (-), affected females transmit the disorder to offspring of both sexes, risk of affected offspring 50%, but twice as many affected females as affected males (no male to male)
3. A carrier Female for an X-chromosomal mutation has a risk of 50% For an affected son.