mandalian genetics Flashcards
what are the four different types of dominance
1) compleate dominance: one allele is compleatly dominent over the second allele. will completly control the phenotypes
2) incompleate dominance: Neither allele compleatly control the phenotype. Both alleles ‘blend’ to make a new inbetween phenotype. further generations can come out as a 1:2:1 ratio as they can come back.
3) Co dominence: Both the alleles phenotypes are exspressed.
4) polygenetic traits: Phenotypes which are exspressed by multiple genes. they all contribute to the exspressed phenotype
What is the point of a cross test
crossing a recessive phenotype with dominent phenotype to find out if its homo or hetrozygous
what is a dihybred cross
a cross between two hetrozygous parents.
what ratio will be exspected for a dihybread cross between 2 different dihybreds,
1;3;3;9
What are mandals 2 laws
The law of seggergation: the seperation of homologs during meiosis 1. only 1 allele in each gamete
The law of independant assortment: the location of one gene when lining up is independant of where a different gene goes.
What is a polymorphic trait
one which has many alleles in the popualtion
What effect does the enviroment have on the overall phenotypes
smoothes the differences between phenotypes dependant on how much of an effect which the enviroemnt has changes how apparent this change is. makes it harder to work out genotype from phenotype
what is a sex linked trait
a trait which is linked to the x chromosome, will have a different proporton of males and female (due to inheritance of XX compaired to XY)
What are the ratios of inheritance for the situations: muation = 1 x chromosome with a genetic defect
male has mutation:
female has mutation:
both male and female have mutation:
If XY has X linked defect all daughters will be carriers and no males will be carriers
If XX has the mutation then Half the females will be carriers and half the males will be carriers
If both XX and XY have the mutation then 1/2 the females will exspress this trait, 1/2 the males will be carriers and 1/2 the females will be carriers, 1/2 the males will show no defect
What does hemizygous mean
what does homo/hetro gametic mean
Hemizygous: An x linked trait in a male who only has 1 copy of this gene, hemi (1) zygous (gene)
homo/hetro gametic: homo - same sex chromosome XX
hetro - different sex chromosomes, XY
Linked genes shows what inheritance patturn , why is this not a perfect rule
linked genes show bais toward the parental phenotype . wont be perfect due to crossing over at mieosis 1
How to calculate recombination frequency and what does it mean
Number of modified (unexspected phenotypes) / total population
The ratio of offsping which was impacted by crossing over, the higher this number the further away the genes are due to having a higher chance of a chiasmata between the two genes forming.
Why do the parental phenotypes become more common why crossing hetrozygotes with homozygote ressestive with xlinked
The two dominent phenotypes are dependant on one annother same with the ressesive, they are not independant events.
this means that the phenotypes will be showing the parental phenotype more fequently.
Recombinenet frequency calculations are worked out how?
RF = (number of recombinents)/(total population)
to work out in cM (centrimorgans)
RF * 100 = cM
