Gregor Mendel test crossed pea plants to see genetically inherited traits. He found the ratios that traits are passed from parents to offspring.
William Bateson and Reginald Punnett
They crossed doubly heterozygous genes to see at what ratios the offspring inherited the traits which led them to discover linked genes and the punnett square.
Thomas Hunt Morgan
Morgan bred fruit flies to see inherited eye color. He saw that only males had some whites eyes which led him to discover crossing over, genetic recombination, and gene mapping
Garrod observed inherited dieses , proposed that inherited dieses is a persons inability to produce a particular enzyme which led to the discovery of the relationship between genes and proteins.
Griffith injected rats with lethal and non-lethal strands of pnumonia. He then killed the lethal with heat then mixed it with the non-lethal. The resulting mixture was lethal to the rats. This experiment led him to discover transformation.
George Beadle and Edward Tatum
Beadle and Tatum experimented with mutant nuerospora and crossed it with normal nuerospora which led them to discover that a certain enzyme belongs to a certain part of DNA.
Chargaff studied Adednine, Guanine, Thymine, and Cytosine using models of DNA. This led him to discover the base pairing rules, amount of Adenine = amount of Thymine and amount of Cytosine = amount of Guanine.
Alfred Hershey and Martha Chase
Hershey and Charse confirmed that DNA was the genetic material by using radioactive DNA and proteins. When they blended them together they found the radioactive DNA remained which led them to conclude that DNA is the genetic material, not proteins.
Maurice Wilkins and Rosalind Franklin
Wilkins and Franklin took X-ray crystallographic photos of DNA which was used to determine DNA is a helix.
James Watson and Francais Crick
by using photos taken by Rosalind Franklin Watson and Crick discovered that DNA is a double helix and found nitrogen bases.
Nirenberg synthesized artificial DNA by linking together two identical strands of DNA with uracil as the base which led him to discover that the RNA condor aaa specifies phenyloline and what all the Condors produced.