Theodor boveri 1896 and walter sutton 1902

1. Theodor boveri 1896 andwalter sutton 1902

2. Theodor Boveri Performed cross-breeding experiments on sea urchins producing hybrids Noticed some eggs from the female contained no nucleus. He was still able to fertilise them with male sperm and the resultant offspring were not a hybrid but a smaller version of the male parent. Boveri concluded that is was the something in the nucleus that was responsible for the inheritance of characteristics and not in the cytoplasm.

3. Walter Sutton Followed work of Boveri (and other scientists) he concluded that: # Mendel’s “factors” are located on the chromosomes # Chromosomes occur as homologous pairs # As a result of meiosis, each gamete receives only one chromosome of each pair # The distribution of each member of a homologous pair is independent Meiosis Meiosis again - simple

5. SEGREGATION: Copies of the same gene occur in pairs on homologous chromosomes Gene for widow’s peak Mum’s copy Dad’s copy Only one from each homologous pair ends up in each gamete 1 homologous pair Gamete 1 Meiosis occurs Gamete 2

6. INDEPENDENT ASSORTMENT: One gene pair will separate independently of other gene pairs on different chromosomes OR FOUR DIFFERENT types of gametes

7. CROSSING OVER: During meiosis homologous chromosome pairs sometimes touch and exchange genes.

8. Walter Sutton Idea not accepted, most scientist believed that each chromosome contained ALL the information for that organism. Theodor Boveri Continued his work with sea urchins and was able to show that each chromosome had different information and each one was needed for the organism to survive. Sea urchin eggs fertilised with two sperm, when these eggs began to divide the new cells had different combinations of chromosomes