Genetic Inheritence Flashcards
Allele Def.
Copy of a gene with slight variation in DNA base sequences
Homozygote Def
Alleles are perfectly identical
Heterozygous Def
Alleles are different by a few base sequences
Genotype Def.
Genetic constitution
Phenotype def.
Physical appearance
How inheritence patterns are identified
Pedigree analysis and DNA sequencing
Mendelian Inheritance Patterns List
Autosomal dominant, autosomal recessive, x-linked dominant, x-linked recessive and y-linked
Autosomal Dominant
Dominant allele in non-sex pair is defective. Physical disease presents in both heterozygous (most frequent) and homozygous (more intense) conditions. Patients tend to die before reproductive maturity. Both sexes effect and both transmit. Offspring have disease phenotype 50% of the time
Autosomal Dominant Disease Example
Familia Hypercholesteremia: Increase in cholesterol due to damaged LDL receptors. Leads to
Exceptions to Autosomal Dominant Disease Progression
Mutation, Reduced penetration and variable expression
Reduced Penetration Outline
The reduction in proportion of people with given genotype presenting specific phenotype
Variance in Expression Outline
Difference in diasease phenotype severity
Carriers Def.
Individuals with 1 disease allele and 1 compensating allele. Don’t present with disease phenotype
Haploinsufficiency Def.
Disease requires > 50 % of protein produced by chromosome pairs to not appear in phenotype. Presents in both hetero and homzygous
Dominant Effect def.
Protein produced by disease gene impedes normal allele function
How 1 gene can cause disease phenotype
Haploinsufficiency, Dominant effect, gain of function and loss of hetrozygosy
Gain of Function Outline
Disease allele has improved function. Eg Huntington’s blockage of protein at end of neurons results in damage
Loss of Heterozygosity Outline
Carcinogens damage DNA containing healthy allele thus body depends on diseased allele
Autosomal Recessive Outline
Disease phenotype in recessive homozygotes. Heterozygotes are carriers. Tend to affect all siblings in 1 generation (doesn’t effect multiple generations). All sexes equally effected. Carrier and Non have 50% chance of offspring disease phenotype and 50% carrier
Why do males and females produce same amount of sex-linked protein though males are hemizygous
1 of females 2 X-chromosomes is wound too tightly around a histone for transcription to occur
Barr Body Def
Permanently condensed heterochromatic chromosome. Stains darkly
Adult female mosaic
Mass of cells that both cells withactive x-chromosomes from the paternal line and cells with active x-chromosomes from the maternal line
Intermediate Effect Def.
Patient is clinically unaffected (no disease symptoms) but has biochemical abnormalities
Skewed x inactivation
More genes programming for diseased protein is inactive
