Chapter 5- Complicating Inheritance Flashcards

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1
Q

Factors influencing inheritance

A

Multiple Alleles
Codominance
Incomplete dominance
Penetrance
Heterogeneity
Mitochondial genes
Linkage

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2
Q

Multiple Alleles

A

More than two forms of allele in population
Individual expresses at most two
Examples- ABO blood types and HLA Genes

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3
Q

Codominance

A

Heterozygotes express both alleles
Example- ABO blood types

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4
Q

Epistasis

A

Multiple gene interactions on phenotype

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5
Q

Labrador Coat Phenotypes

A

Gene B controls melanin density
Dominant- black coat, recessive- brown
Gene E controls deposition
Dominant- Normal, recessive- None, yellow
Gene D controls melanin production
Dominant- Full, normal; recessive- dilute, silver

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6
Q

Penetrance

A

Chance that an individual with a particular allele with display the phenotype
Reduced penetrance- Some individuals will no show symptoms
Autosomal dominant heritability

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7
Q

Variable Expression

A

Expression of different degrees of the phenotype, varying severity
Will always show some symptoms
Causes- Environment, modifier genes, Allelic heterogeneity

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8
Q

Allelic Heterogeneity

A

Many different mutations on same gene cause similar diseases

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9
Q

Locus Heterogeneity

A

Mutations on different genes can cause similar diseases
Example- Polycystic kidney disease can result from mutations on chromosome 16 or 4

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10
Q

Pleiotropy

A

Single genotype causes many phenotypic expressions
Impacts many bodily systems

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11
Q

Phenocopy

A

Environmental influences cause traits that appear to be inherited

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12
Q

Huntington’s Disease

A

Autosomal dominant progressive brain disorder
Mutation of Huntingtin (HTT) gene
Expansion of glutamine triplets cause misfolding and protein aggregation
Impair basal ganglia function
Defects in motor, cognitive, and psychiatric domains

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13
Q

Mitochondrial Genome

A

Independent, unique
37 genes- 13 ETC, 2 rRNA, 22 tRNA
Many copies
Maternal inheritance
High mutation rate
Heteroplasmy

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14
Q

Heteroplasmy

A

Copies of mitochondrial DNA are not identical
Segregation during cell division is random and unorganized
Phenotype is dependent on if mutant DNA is above threshold

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15
Q

Mitochondrial Disease Pedigree

A

All children regardless of sex inherit DNA
Only develop symptoms if above threshold
Maternal transmission only

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16
Q

Leber’s Hereditary Optic Neuropathy (LHON)

A

Sudden bilateral blindness ~27 years old
Reduced penetrance
Defects in NADH dehydrogenase

17
Q

Linked Genes

A

Close together loci that do not segregate independently
Inherited together as haplotype
Recombination rate less than 50%

18
Q

Genetic Mapping

A

1% recombination = 1 map unit
1 map unit = 1 centimorgan (cM)
Recombination frequency= recombinant progeny over total progeny

19
Q

Human Gene Mapping

A

Collect pedigrees of families with disease of interest
Analyze genetic markers throughout genome
Perform statistical analysis
Compared linked genes with pedigree data
Analyze linked gene functions for mechanism

20
Q

Genetic Statistical Analysis

A

LOD Scores
Odds genes are linked on the same chromosome
LOD score over 3 is significant

21
Q

Amyotrophic Lateral Sclerosis (ALS)
Lou Gehrig’s Disease

A

Progressive lethal motor neuron disease
Kills motor neurons in brain and spinal cord
Death by muscle atrophy and diaphragm paralysis
Familial mutations in SOD1 gene encoding CuZn superoxide dismutase
Abberant chemistry or protein aggregation causes cell death