Lecture 14 Flashcards
How is Gene linkage an exception to Mendelian Genetics?
Genes on the same chromosomes do not assort independently of each
How are Sex linked genes an exception to Mendelian Genetics?
Sex linked genes do not exhibit the same ratios in both sexes
How is incomplete dominance an Exception to Mendelian genetics?
In a dihybrid cross it will give a 1:2:1 ratio
How is Incomplete penetrance an exception to Mendelian genetics?
Sometimes individuals with a certain genotype do not have the corresponding phenotype
What is Variable expressivity?
Differences in the strength of a phenotype within individuals
How is Variable Expressivity an exception to Mendelian Genetics?
This changes the expected phenotypes
How is Functional Mosaicism an exception to Mendelian Genetics?
When there is random inactivation of an X chromosome the phenotypes may vary
What is the shape of DNA in mitochondria?
Circular, with multiple copies throughout the cell
What is union rental inheritance?
When organelles in a cell are either inherited from the mother or the father but not both
What is Homoplasmy?
When all mtDNA copies are identical
What is Heteroplasmy?
When there is a mixture of mutant and normal mtDNA copies in a cell
What genes are encoded for in mitochondrial DNA in humans?
Genes for oxidative phosphorylation
Ribosome components
Translation machinery like tRNA
What does a pedigree look like for a mitochondrial disease?
The mothers pass it on to all their children and affected fathers never transmit to offspring
Why does LHON occur?
Because mitochondria are very important in retinal cells mutation in this will cause the disease
What can cause Heteroplasmy?
When mitochondria replicate they divide by binary fission. Since there are multiple copies of mitochondrial DNA within the mitochondria they do not get distributed evenly so some may have multiple copies of the mutant DNA while some get normal copies. Also in gamete formation there isn’t even distribution of mitochondria so some may receive mitochondria with more of the mutated DNA
How is embryonic lethality an exception to Mendelian Genetics?
Embryonic Lethality will affect the ratio of genotype. For example a homozygous dominant condition will cause the embryo to die before being born
What would be the ratio if we observed Gene redundancy?
15:1 in the “other” phenotypic ratio
What cause an organism to still appear wild type even though reverse genetics has removed a gene?
The researcher may not be looking in the correct place/testing the correct condition
The gene may have subtle effects on the fitness and species
It could also be due to gene redundancy where one gene compensates for the loss of function of another
What are duplicate genes in gene redundancy known as?
Paralogs
What is the ratio in Recessive Epistasis?
9:3:4
What is Epistasis?
When an allele of one gene masks/influences the phenotypic effects of the alleles of the other gene
What is Recessive Epistasis?
When the phenotype of homozygous recessive alleles conceals the phenotype of either allele from a different gene
What is Dominant Epistasis?
When the phenotype of a dominant allele conceals the phenotype of wither allele from a different gene
What is the Ratio in Dominant Epistasis
12:3:1
What is the ratio in complementation?
9:7
What are Conditional Mutations?
Mutations that have a Wilde type or less severe phenotype under certain (permissive) environmental conditions
When is the mutant phenotype seen in conditional mutations?
At non-standard temperature is the mutant phenotype is expressed. This temperature is called the restrictive temperature
What causes Conditional mutations?
Usual missense mutations
