Presentation on theme: "11-5 LINKAGE & GENE MAPS. 1. GENE LINKAGE Thomas Hunt did research on Drosophila ( fruit flies) From the experiment scientist learned that genes located."— Presentation transcript:
11-5 LINKAGE & GENE MAPS
1. GENE LINKAGE
Thomas Hunt did research on Drosophila ( fruit flies) From the experiment scientist learned that genes located on the same chromosome are inherited together A fruit fly (Drosophile)
Genes are linked or inherited together in “linkage groups” Each c’some is a group of linked genes Mendel’s principle of independent assortment is still true. Chromosomes assort independently Individual genes do not assort independently
2. GENE MAPS
Crossing over during meiosis can sometimes separate and exchange linked genes which results in new combinations of alleles. This helps increase genetic diversity.
Alfred Sturtevant studied Drosophila (fruit flies) and crossover rates b/w genes far apart on a chromosome. The farther apart a gene is on a chromosome the less likely they will crossover together during meiosis Alleles “A” and “E” are less likely to crossover together b/c they are farther apart from each other
Gene map- shows the location of a gene on a chromosome. Gene maps can be used to calculate recombination frequencies. Genes that are close together have a low recombination frequency (crossovers are rare). Genes that are farther apart have a high recombination frequency (crossovers are likely).
COPYRIGHT PEARSON PRENTICE HALL GENE MAPS Aristaless (no bristles on antenna) Chromosome 2Exact location on chromosome 13.0 Dumpy wing Black body 54.5 Purple eye 67.0 Vestigial (small) wing 99.2 Arc (bent wings) Speck wing
COPYRIGHT PEARSON PRENTICE HALL Chromosome 2Exact location on chromosome 1.3 Star eye 31.0 Dachs (short legs) 51.0 Reduced bristles 55.0Light eye 75.5 Curved wing Brown eye GENE MAPS
You and your partner draw a hypothetical gene map in your notebook,. Which genes would have high frequencies of crossing-over, which would not?