Modification of Mendelian Ratios Flashcards
(22 cards)
Mendels Laws
Mendels Laws
- Parents Alles will be divided Randomly into gametes - each gamate will recive one allel or the other, stats with equal likelihood
- Each trait is inherited independently of every other trait - separate genes are not inherited together they assort independently
Was mendel Wrong?
Was Mendel Wrong?
Why do some phenotypes not fit the 3:1 ratio?
* Multiple Genes controlling one trait
* One gene controlling multiple traits
* Multiple alleles in one gene
* Alleles neither dominant or recessive
* Enviormental effects on trait
Altering Mendels Ratios
Altering Mendels Ratios
- Genotypic Ratios follow mendels laws, but phenotypes do not - somehow the underlying genotypic ratios are hidden
- Mendels laws do not apply - both genotypes and phenotypes are not following mendels laws
Type 1 - Laws in Effect
Type 1 - Laws in Effect
- Lethal Genotypes
- Incomplete Dominance
- Co-dominance
- Allelic Heterogeneity
- Genetic Heterogeneity
- Epistasis
- Pleiotropy
- Sex Dependent Traits
- Penetrance
- Expressivity
- Tempature Dependnet Expression
- Phenocopy
Type 2 - Mendels Laws No Longer Apply
Type 2 - Mendels Laws No Longer Apply
- Non-nucular inheritance: mitochondria and chloroplasts have their own DNA, which is soley maternally inherited
- Linkage: Two genes that are so close together physcially that they are inherited together
Type 2 - Mendels Laws No Longer Apply
Type 2 - Mendels Laws No Longer Apply
- Non-nucular inheritance: mitochondria and chloroplasts have their own DNA, which is soley maternally inherited
- Linkage: Two genes that are so close together physcially that they are inherited together
Lethal Alleles
Lethal Alleles
Mutations in genes that are necessary for survival cannot exist
* Often tolerated in heterozygotes because some protein is still made
* Lethal in homozygote mutant
Incomplete Dominance
Incomplete Dominance
- Neither allele dominants over the other
- Producing an intermediate phenotype
- Homo Dom (RR) = red flowers
- Homo Rec (rr) = White Flowers
- Heterozygoutes (Rr) = pink Flowers
Codominance
Codominance
Both Alleles are expressed equally
* Phenotype determined by both alleles
* Not intermediate, but a third phenotype
Multiple Alleles
Multiple Alleles
- one gene can have many different alleles, phenotype may be determined by which two alleles are present in individual
- Allelic Heterogeneity
Multiple Genes
Multiple Genes
- Other times a single trait will be controlled by more than one gene
- Genetic heterogeneity
- Phenotype not determined by inheritance of two alleles of one gene - but instead alleles of all the genes
Seperate Complications
Seperate Complications
How can one tell if complication caused by more than one alele or mutation
* Allelic Heterogeneity
Or more than one gene
* Genetic Heterogeneity
You must do a complimentation analysis
Epistasis
Epistasis
- Protein from one gne interacts, modifies or masks the protein from onther gene
- Either because: Two genes interact, or because both genes affect same phenotype
Pleiotropy
Pleiotropy
One gene controls more than one trait
* Pleiotrpy occurs when one genes controls more than one pathway or is expressed in more than one body part
X-Linked Genes
X-Linked Genes
All the genes on the sex chromosome (X) have differential Inheritance dependent:
* Sex of Parent
* Sex of offspring
* Males are neither Homo or Hetero they are Hemizygous (XY)
* males dont pass X chromsome to their sons, only to their daughter
Pedigree Analysis
Pedigree Analysis
X-Linked Recessive
* More males are affected
* Passed from affected mothers to all sons
* Affeced fathers will only transmit to heterozygous, unaffected daughters
X-Linked Dominant:
* Males and Females both affected
* Affected mothers to half of children
* Affected fathers to every daughter affected
Sex limited Traits
Sex limited Traits
Traits expressed in body parts that onlt exist in one sex and not other
Sex Influenced Traits
Sex Influenced Traits
Traits that exist in both sexes, but gene expression is influenced by hormone level
- Ex. male Patern Baldness
Modifying Forces
Modifying Forces
- Hormone Levels are one example of an outside force interacting with a gene
- A multitude of these forces exist: External Enviorment, And the inside the cell (other proteins)
- Modifying the expression of phenotype by: interaction of gene with enviorment, interaction with other genes
Penetrance vs. Expressivity
Penetrance vs. Expressivity
Both follow mendels laws:
* Genotypic ratio is still 1:2:1
* Phenotypic Ratio is affected
Both have to do with amount of phenotype present
* Penetrance: all or none offsrping is affected or not
* Expressivity: is the severity of the phenotype offspring show a range of phenotypes
Tempature - Expression
Tempature - Expression
ex. Body Tempature during development can affecr expression of phenotype
* Siamese Pigmentation
* Enzyme for pigment only works in cool tempatures
Phenocopy
Phenocopy
Trait that is not genetic at all
* An enviormentally caused trait that apperas to be inherited in famililes
* an enviormentally caused phenotype that mimics a known inherited Phenotytpe
* Dosent produce mendelian ratios because its not actuallt controlled by genes
