MBG Flashcards
Wildtype Allele
A functional enzyme or other protein is produced
-Referred as a most common phenotype or genotype found in natural population
Loss of function allele
-an enzyme or protein is no longer produced
or it is produced at lower levels or nonfunctional
Biochemical definition of a Wildtype
- the wildtype allele is dominant over the loss of function allele
- half as much protein is synthesized yet this is often sufficient to achieve the wildtype phenotype
- This is called halposufficiency
Haplosufficiency
- Half as much protein is synthesized yet this is often sufficient to achieve wildtype phenotypes
- half is enough, 1 copy is backup
not always is it that the dominant allele is normal and the recessive allele is a mutation
-Dominant alleles can be a gain of function mutations, in which the mutant allele produces a protein that has increased detrimental function
Dominant allele can be a loss of function alleles
-In the heterozygote half as much protein is synthesized and that is not enough for a normal phenotype-halposufficient (tailles cat)
Heterosis
- When two different inbred lines are cross, the hybrids are heterozygous for many genes
- These heterozygotes display heterosis, or hybrid vigor
- Inbreed increases the frequency of homozygotes and decreases the frequency of heterozygotes.
Hardy Weinberg principle
- Predicting genotypes through allele frequencies in a population
- p+q=1 (when there are two alleles present, if there are three like in the ABO blood then it would be x+y+z=1)
- p^2+2pq+q^2
- 2pq= 1allele generated from mom or the same allele generated from the dad
- The Hardy weinberg principle is used to predict genotype based on the allele frequency.
Conditions for the Hardy-Weinberg Principle
it is not valid if it is…..
- Non random mating (we are sexual selective)
- Unequal survival (due to enviromental forces)
- Population division (1/4 is not a representation of a whole pop’n) it is not the rep of the whole gene pool
For problems with Hardy Weinberg
- you are always give the allele frequency
- allele frequency represents either the recessive gene (q) or dominant (p)
- when you figure out what you have you can find the other variable p or q using this formula p+q=1
- if it says what is a chance to be a carrier then it is 2pq
- if there is a chance to be recessive then it is q^2
- if the child is affected then use the punnet square with the carrier allele that you calculated and the chances of it being passed down (1/2)
Dosage compensation
- It is a way of equalizing gene expression in the face of different gene dosage.
- Humans are sensitive to gene dosage, we need only 2
- If there are more than 2 in the autosomal/somatic chromosome then it will cause a miscarriage in the womb
How do the X and Y chromosomes pair even though they are not homologous?
-The X and Y chromosome are ONLY homologous at the PSEUDOAUTOSOMAL REGIONS, which are essential for X-Y pairing in a male in meiosis
X innactivation
- in mammals not only females
- Every cell chooses a random x to inactivate
- unique of sex chromosomes
- they are viable bc of the x inactivation
- autosomal change means you die
- inactivate the x chromosome bc of the dosage compensation
Lyon Hypothesis and X inactivation
- Mary Lyon proposed the random inactivation of x chromosome
- if a cell contains more than 2X chromosomes all but one of them are inactive
- Condensed mass is called a Barr Body
- XO have no Barr bodied, XXX have two barr bodies
- They are HEMIZYGOUS for x linked genes
- 50 percent express one alle and 50 precent of cells express the other allele
HEMIZYGOUS
Only one copy is present in a diploid organism
