Genetic Mapping Linked Genes

The chromosome Several genes or alleles are found on each chromosome at a particular locus (position) Locus

Recombinants Recombinants- offspring that exhibit genotypes different from either parent

Mendelian Inheritance Genes that follow Mendel’s inheritance patterns are not on the same chromosome Y y y y r r R r

Genotype ratios come out as expected

Linked Genes Linked genes- genes that are on the same chromosome and are generally inherited together (don’t follow Mendel’s laws)

Recombinant Frequency When a lower percentage of recombinants show up than was expected, we know that genes are linked. (or a higher percentage of parental types)

Linkage Map An order of gene loci along a chromosome based on recombinant frequencies (the further apart the chromosomes are, the higher the probability of them crossing over)

Testing Recombinant Frequencies A Chi Square test can be done to see if there is a statistical difference in what you expect and what you observe. N=Normal wings n=wingless flies Nn x Nn Expected ? Observed 522 winged 202 wingless

1st Make a null hypothesis A null hypothesis says that there is no difference between what you expect and what you observe Is there a difference ?

2nd Run the numbers X2= Σ(o-e)2 e

3rd Get you values X2= calculated chi square value df=degrees of freedom- the number of categories (n) minus 1 Confidence interval- how sure you can be in the outcome (we usually use 95%)

4 look up your values Look up you values in the table. If your chi square value is less than the value on the table than except the null hypothesis.

Analyze An accepted null means what you expected is what you observed A rejected null means what you expected is significantly different that what you observed.