9 22 Lecture Revised notes Genetics Mendel assumed Genetics after Mendel no one understood because of the math involved although trivial 1 Traits are due largely to the action of a single factor BUT MENDEL WAS WRONG most traits are polygenic height skin color disease predisposition Concept of Polygene Inheritance Most traits are determined by several genes at different places of chromosome CODOMINANCE When 2 alleles are together but both are shown Blood Type Mendel also assumed that his factors only affected 1 trait FALSE some genes affect many traits Concept of Pleiotropy 1 gene controls more than 1 characteristic Chromosomes discovered in 1875 They are arrainged linerally We know where all the major genes are located on the chromosomes Unless in nuclear division genetic material is unraveled and called chromatin is made up of protein and DNA Chromatin Humans 46 chromosomes diploid 23 pairs Human karyotype chromosome pattern Polyploidy 3n 4n 5n Happens in cells like liver or intestinal Possible to have more than 2 sets of chromosomes 22 pairs of autosomes code for body and function 1 pair of sex chromosomes mostly sex characteristics Particular place of a gene LOCUS Sister chromosomes carry alleles in the same position one from mom one from dad Linkage Genes on the same chromosome are linked Cell division Most cells go through mitosis Before this happens cells must duplicate Step 1 The chromosomes duplicate providing 2 identical arms each with same alleles Moment its ripped apart 2 chromosomes Step 2 Chromosomes are lined up Step 3 Chromatids pulled apart Step 4 46 chromosomes on each cell 1 chromosome 2 chromatids once they split 2 chromosomes Look at meiosis chart draw division of sperm and egg cells on sheet Distribution of chromosomes is random sexual recombination variety Crossover sister chromosomes swap during meiosis 1 side by side Crossover can break up linked traits SRY Sex determining region of chromosome