4.6.3.3 The Understanding of Genetics (biology only)

Question 1

What experiments did Gregor Mendel carry out and what were his observations?

Answer 1

• in mid-19th C Gregor Mendel carried out breeding experiments on plants
• one of his observations was that the inheritance of each characteristics is determined by ‘units’ that are passed on to descendants unchanged

Question 2

What is an example of an experiment that Gregor Mendel carried out?

Answer 2

• worked in monastery gardens and observed the characteristics passed on to the next generations in plants
• carried out breeding experiments on pea plants
• used smooth peas, wrinkled peas, green peas and yellow peas and observed the offspring to see which characteristics they had inherited
• through keeping a record of everything he did and eventually publishing his work in 1866 he came to the conclusions that:
  
  • offspring have some characteristics that their parents have because they inherit ‘hereditary units’ from each
  • one unit is recieved from each parent
  • units can be dominant or recessive and cannot be mixed together

Question 3

Why was the importance of Mendel’s discovery not recognised until after his death?

Answer 3

as genes and chromosomes were not yet discovered so people couldn’t understand his idea of ‘units’

Question 4

What was observed in the late 19th C that helped our understanding of genetics?

Answer 4

in late 19th C behaviour of chromosomes during cell division was observed

Question 5

What was observed in the early 20th C that helped our understanding of genetics?

Answer 5

• in the early 20th C it was observed that chromosomes and Mendel’s units behaved un similar ways
• this lead to the idea that ‘units’, now called genes, were located on chromosomes

Question 6

When was the structure of DNA determined?

Answer 6

• the structure of DNA was determined in the 20th C and the mechanism of gene function was worked out
• this scientific work by many scientists led to the gene theory being developed