What are gene interactions?
-Genes sometimes work together
What did Archibald Garrod discover?
English physician who had patients with alkaptonuria he noticed from pedigree that this disease ran in the family so he assumed a genetic component was involved. The affected secreted homgentisic acid people with out it secreted maleylacetoacetic acid. He hypothesized that the people with disease had inborn error in metabolism (error in conversion of homogentisic acid to maleylacetoacetic) they were missing something that did this conversion.
What is alkaptonuria?
arthritic disease that also caused urine to be dark color/black
What did Beadle and Tatum do?
Worked on organism (neurospora crassa) haploid (doesn't have homologous chromosomes) fungi. discovered that one gene= one enzyme or one polypeptide or one functional product.
What are conidia?
filamentous growth called mycelium that forms haploid cells
What are ascopores?
8 cells formed from the 4 gametes of fungi after meiosis 2
What is an ascus?
hold ascopores together
What are auxotrophs?
Neurospora crass fungi that could not grow on minimal media (unable to make something they must have as a mutant gene to survive)
What are prototrophs?
Wild type Neurospora crassa that could grow on minimal media
What did X-rays do to Neurospora crassa?
X-rays shot at Neurospora crassa creates mutations
what is the advantage of using haploid cells?
-see recessive mutation quicker
-simple media requirements
What is a complete medium?
Has all supplements that fungi could be mutated for (allows mutations to thrive)
What is minimal medium?
Does not supply all supplements neccessary for mutated fungi to thrive (Prototrophs could survive in this)
What is Minimal Medium + something?
Used to figure out what types of mutant fungi are present
What is a one gene one enzyme hypothesis?
Each gene is related to the function/creation of one enzyme
What did Beadle and Tatum find in Arginine synthesis and intermediates?
They knew that there were intermediates before arginine. Came up with biochmical pathway of what this chain looked like to get to arginine. They knew the components but not the order. They used the mutants then to help them build this biochemical pathway.
what is Phenylketonuria?
Inabiity to convert phenoalynine to tyrosiene mutation in phenhydorxylase enzyme. Instead it converts into phenylpyruvic acid, which disrupts neurological functions (autosomal recessive disorder)
What is a null mutation?
Allele that makes no functional product
What is a leaky mutation?
Makes a functional product but it doesn't have wild type function (instead a mutant function)
What is a silent mutation?
Does not effect the functional product of a protein
What is an Allelic series?
All the known alleles of a gene
What would occur if you mutated an enzymes promoter? m1,2,3 sites? active site? m5 site?
-promoter: protein won't be made
-m1,2,3: protein is created but won't work/function
-active site:protein created but has mutant function
-m5: gene is changed but doesn't affect functional protein
What is incomplete dominance?
one allele is not completely dominant to another allele (heterozygote genrally has intermediate phenotype in-between 2 homozygotes)
What is an example of incomplete dominance?
-Four o'clock flowers
c. Pink intermediate
What is codominance?
Relationship between alleles in which heterozygotes display the phenotype of both homozygotes
What is an example of codominance?
-A and B both dominate to O
-A and B codominate to eachother
What ratios correspond to a single gene interaction? (Single Gene Test will produce these results)
(3:1) (1:2:1) (1:1)
What is a Complementation Test?
-Mutant + Mutant = Mutant (same gene)
-Mutant + Mutant = Wild Type
(two different genes/ COMPLEMENTATION)
What is a Complementation?
The production of a wild type phenotype when two recessive alleles of different genes are brought together in the same cell/organism
What is a Heterokaryon?
One cell with two nuclei
What are Heterokaryons used for?
-for determining complimentation testing
-Simply fuse two mutant cells together, if they create wild type you know they are compliments
What is the Modified Mendelian Ratio?
- 9:7 (proves there is more than one gene involved)
- 9:3:3:1 (3+3+1= 7) MODIFIED
What is the difference between Combination Phenotypes and Codominance?
Combination= two dominant alleles on two DIFFERENT genes
Codominance= two dominant alleles on the SAME gene
What is a New Phenotype?
When two same phenotypes mate and form a new phenotype
What is Epistasis?
The interaction of non-allelic genes in which one gene masks the expression of another non-allelic gene
What is Recessive Epistasis?
homozygous recessive pair of alleles will mask the expression of heterozygous wild type allele
What is Dominant Epistasis?
Presence of dominant allele will mask the expression of another dominant allele or recessive allele
What is hypostatic?
The allele being masked by an epistatic one
What ratio is characteristic of a double recessive epistatic?
What are Suppressor alleles?
Mutations in one gene that suppress the mutant phenotype that is due to mutations of another gene
What is a Revertant?
Return the mutant gene back into the wild type phenotype
What is expressivity?
Degree to which a phenotype is expressed in an individual
What is variable penetrance?
Frequency with which a gene mutation manifests itself within a population (phenotype percentage in a POPULATION)
What is variable expressivity?
Degree to which a phenotype is expressed (phenotype degree in INDIVIDUALS)
What is a lethal allele?
Allele that causes death in an organism (mutation of an essential gene)
What is an essential gene?
Wild type allele that is essential for life
What is a Dominant Lethal allele?
Causes death in a heterozygous or homozygous state
What is a Recessive Lethal allele?
Only causes death in homozygous state