20.4 Phenotypic ratios Flashcards
what is an autosome?
a chromosome which is not a sex chromosome
what is autosomal linkage?
when the genes found on the same autosome are linked
how are linked genes inherited?
they are always inherited together
what happens to autosomal genes during meiosis?
they stay together during independent assortment of chromosomes
alleles will end up being passed to offspring
what could cause autosomal genes to be split up?
crossing over of chromosomes in prophase I
how does crossing over split autosomal genes up?
genes are exchanges which means that autosomal genes will likely be split apart from each other
thus breaking the linkage
what are recombinant offspring?
offspring which have different combinations of alleles to their parents due to crossing over
the closer genes are on an autosome
the more closely linked they are
the less likely they will be separated during crossing over
SO
less recombinant offspring produced
recombination frequency =
number of recombinant offspring
/
total number of offspring
what does recombinant frequency show?
the degree of crossin over in a pair of chromosomes
more crossing over means more recombinant offspring
if the recombination frequency is 50%
there is no linkage
genes are on separate autosomes
if the recombination frequency is less than 50%
there is gene linkage
how would the phenotypic ratio suggest that there was linkage?
if the ratio has a large number of two phenotypes and a small number of the other two it is likely that there is linkage
if x2 value is less than critical
not enough evidence to reject null hypothesis
there is no significant difference between observed and expected
if x2 value is greater than critical
enough evidence to reject null hypothesis
there is a significant difference between observed and expected
