{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}


Question if proposed genetic mechanism is correct

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: expected values by just chance or variation? or The Chi Square Test Conventional measure of “goodness-of-fit” between observed and expected values is called chi-square expected chi-square Indicates how often an experimentally observed deviation from a particular hypothesis will occur solely by chance from chance • takes into account importance of sample size sample • chi square test is always calculated with actual data - not % or proportions, requires LARGE sample size LARGE When geneticists want to determine if two genes When are linked, they actually test whether the data are consistent with a null hypothesis of no linkage consistent null no • large degree of phenotypic variability if linked • unlinked will assort independently to produce 50% parental and 50% recombinant in F2 50% If the chi square test shows that the observed If observed data differ significantly from what would be significantly expected with independent assortment, the null hypothesis is rejected -genes could be linked Applying The Chi Square Test Applying First: -state the genetic hypothesis in detail First: • (YyRr x yyrr) will yield an F2 ratio of 1:1:1:1 if genes assort independently -not linked Use the data obtained from a breeding experiment Use to determine: to the total number of offspring total the number of different classes of offspring (phenotypes) (phenotypes) and the number of offspring observed in each class number 568 progeny with 154 Y_R_:144 Y_rr:124 yyR_:146 yyrr 568 154 Total offspring = 568 568 Number of different classes of offspring = 4 Number observed in each class = 154:144:124:146 154:144:124:146 2. Calculate the number of offspring that would be expected for each class if the null hypothesis expected were correct (percentage predicted x total were number of offspring) number Expected values: (1/4 x 568): (1/4 x 568): (1/4 x 568): (1/4 x 568) = 142:142:142:142 The Chi Square Test The Deviation from predicted χ2 = Σ 3. Class (Number observed-Number expected)2 Number expected Y_R_ Y_R_ Number observed = 154 Number expected = 142 =Σ Y_rr Y_rr 1...
View Full Document

{[ snackBarMessage ]}

Ask a homework question - tutors are online