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36 Cards in this Set

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Autosomal Dominant Inheritance
* Each child has 50% chance of inheriting the mutation
* No skipped generations
* Equally transmitted by men and women
* HETEROZYGOTES express the trait
* Vertical transmission from one gen to next
* Structural genes are often involved
* New mutations are common
Incomplete Penetrance
* A trait that is NOT expressed in the phenotype of a gene carrier
* IE: Breast Cancer occurs in about 70% of BRCA1 gene mutation carriers
* Other genes or environmental factors influence gene expression in these traits
Complete Penetrance
* A genetic trait that is expressed in the phenotype
* IE: (Achondroplasia, and neurofibromatosis)
Variable Expression
* Genetic mutation associated with more than one phenotype
* Intrafamilial variability may be due to interaction with other genes or environmental factors
* IE: Van der Woude
* Interfamilial variation may be due to the effect of different mutations within the same gene
Autosomal Recessive Inheritance
* HOMOZYGOTES express the trait
* Horizontal pattern of transmission within a sibship
* Transmitted by both sexes
* Offspring of carrier parents are at 25% RISK
* Functional genes are often involved
* IE: Sickle cell disease
* Consanguinity is more common
X-linked Recessive Interitance
* HEMIZYGOTES are affected, heterozygotes are carriers
* When lethal, transmitted by FEMALES only (ie: Duchenne Muscular Dystrophy
* When not lethal, transmitted by both sexes (IE: color blindness)
* Sons of carriers mothers at 50% RISK, sons of affected fathers at no risk
Anticipation
* The phenotype becomes more severe or evident at a younger age of onset with each successive gen.
* IE: Myotonic dystrophy
* IE: Premutation for Fragile X in a normal transmitting male expands during female meiosis in his unaffected daughter to a full mutation in her affected son. (Expansion of X chromo because one X doesn't match up with the other and so during crossover, get expansion of X)
Autosomal Dominant Inheritance
* Each child has 50% chance of inheriting the mutation
* No skipped generations
* Equally transmitted by men and women
* HETEROZYGOTES express the trait
* Vertical transmission from one gen to next
* Structural genes are often involved
* New mutations are common
Incomplete Penetrance
* A trait that is NOT expressed in the phenotype of a gene carrier
* IE: Breast Cancer occurs in about 70% of BRCA1 gene mutation carriers
* Other genes or environmental factors influence gene expression in these traits
Complete Penetrance
* A genetic trait that is expressed in the phenotype
* IE: (Achondroplasia, and neurofibromatosis)
Variable Expression
* Genetic mutation associated with more than one phenotype
* Intrafamilial variability may be due to interaction with other genes or environmental factors
* IE: Van der Woude
* Interfamilial variation may be due to the effect of different mutations within the same gene
Autosomal Recessive Inheritance
* HOMOZYGOTES express the trait
* Horizontal pattern of transmission within a sibship
* Transmitted by both sexes
* Offspring of carrier parents are at 25% RISK
* Functional genes are often involved
* IE: Sickle cell disease
* Consanguinity is more common
X-linked Recessive Interitance
* HEMIZYGOTES are affected, heterozygotes are carriers
* When lethal, transmitted by FEMALES only (ie: Duchenne Muscular Dystrophy
* When not lethal, transmitted by both sexes (IE: color blindness)
* Sons of carriers mothers at 50% RISK, sons of affected fathers at no risk
Anticipation
* The phenotype becomes more severe or evident at a younger age of onset with each successive gen.
* IE: Myotonic dystrophy
* IE: Premutation for Fragile X in a normal transmitting male expands during female meiosis in his unaffected daughter to a full mutation in her affected son. (Expansion of X chromo because one X doesn't match up with the other and so during crossover, get expansion of X)
Parent of Origin Effect
* Phenotype varies depnding on which parent transmits the abnormal allele
* METHYLATION patterns differ in male and female meiosis: some genes active only when inherited from one parent (IMPRINTING). IE: Angelman syndrome-maternal copy of gene is active, paternal gene is inactive.
* In utero factors can affect severity, IE: Congenital myotonic dystrophy. Methyl groups cloak DNA and make some genes active and some genes inactive.
Polygenic Traits (Non Mendelian Inheritance)
* Many genes each make a small contribution to the phenotype.
* IE: Intelligence, height.
Multifactorial Traits (NonMendelian Inheritance)
* Few genes make a major contribution to the phenotype in permissive env't
* IE: Spina Bifida, MTHFR, and Folate
Mosaicism (Non Mendelian Inheritance)
* A mutation affects only some cells in the body with a variable phenotype
* IE: Gonadal mosaicism in an unaffected parent causes more than one affected child with OSTEOGENESIS IMPERFECTA TYPE II, lethal autosomal dominant trait.
Chromosomal translocations (NMI)
* IE: Down syndrome
Maternal Inheritance (NMI)
* IE: MITOCHONDRIAL GENOME is cytoplasmic so mitochondrial defects are passed down in the egg cyto from mother to all of her children
Genotype/Phenotype Correlations
* Diff mutations in same gene can cause different syndromes
Genetic Heterogeneity
* Mutations in different genes can cause the same disease
* IE: Mutation in BRCA1 and BRCA2 can both cause hereditary breast and ovarian cancer
Comparative Genomic Hybridization (CGH) to Metaphase Chromosomes
* Test Genomic DNA of Patient and have Reference Genomic DNA hybridize on chromosome to search for duplications and deletions
* Increased ratio will show on the graph for position on chromosome
Polymorphism
* DNA sequence changes that do NOT alter protein function
Disease-Associated Mutations
* A mutation is a change in the normal base pair sequence
* Commonly used to define DNA seq changes that alter protein function
Missense Mutations
* Changes to a codon for another aa (can be harmful mutation or neutral polymorphism)
Nonsense Mutations
* Change from an amino acid codon to a stop codon, producing a shortened protein
Frameshift Mutations
* Insertion or deletion of base pairs, producing a stop codon downstream and (usually) shortened protein
Splice-Site Mutations
* A change that results in altered RNA sequence
Preparing for DNA for Analysis
* Blood sample
* Centrifuge and extract DNA from white blood cells
* DNA for analysis
Electrophoresis of DNA
* DNA fragments loaded into the wells
* DNA fragments separate by size and charge with constant voltage gradient running through gel
Linkage Analysis
* Looks for pattern of DNA markers near gene of interest that segregate with disease
* Requires DNA analysis of multiple family members
Allele Specific Oligonucleotide (ASO) Hybridization
* Amplify DNA and hybridize membranes
* Add radio-labeled normal DNA probes
* Add known mutant DNA probes
Single Strand Conformational Polymorphism (SSCP)
* DNA is denatured into single strands
* Single strands fold; shape is altered by mutations
* Mobility of mutant and normal strands differ in gel
Heteroduplex Analysis (CSGE)
* Amplify and denature DNA
* Single-strand DNA
* In the cold, reanneal DNA
* Get mutated bands vs. normal band
Protein Truncation Assay
* DNA transcribed to mRNA
* RNA translated to protein
* Protein run on gel
* Truncated protein has different mobility in gel.