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Gregor Mendel Discovers Trait Inheritance
Gregor Mendel was an Austrian Monk who test-crossed pea plants in his backyard to see what gene was inherited. Specifically he looked at how the shape and colors of the peas changed over generations. He was the first to discover trait inheritance. He was also the first able to show that when traits are inherited, they follow specific patterns. Unfortunately his work was not recognized until the early 20th century. These laws, that were later discovered, were named after Gregor Mendel. -
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The Major Discovories in Genetics
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William Bateson and Reginald Punnet Expand on Mendel's Studies
William Bateson and Reginald Punnett, two English scientists, are famous for finding an inheritance pattern, which was inconsistent with the data that was expected from the Mendelian Principles. They crossed 2 heterozygous traits (color and pollen shape) in sweet pea plants. They knew that there was an exception to the Medelian Principles, but they did not know what it was. A few years later, other studies revealed that the genes for flower color and pollen shape are on the same chromosome. -
William Bateson and Reginald Punnett (Continued)
Today we refer to this as linked genes. In addition to these studies, Reginald Punnett is famous for his discovery of the Punnett square, which allows us to predict the outcomes for traits. -
Thomas Hunt Morgan Discovers Crossing Over
Thomas Hunt Morgan was another scientist to further expand on the Mendelian Principles. He came to this discovery when studying a fruit fly, called the Drosophila. He crossed one with a gray body and long wings, with one that had a black body, and vestigial wings. He found that 17% of the offspring were recombinants, or offspring that are unlike the parents. He then came to the conclusion that these traits were linked genes, but somehow the linkages broke. Eventually tests proved him to -
Thomas Hunt Morgan (Continued)
be correct, proving that it was crossing over that caused these "breaks" in the linkages between genes. The concept of crossing over is crucial to the study of genetics. -
Archibald Garrod (Continued)
science because if someone has a disease, is can be cured by an individual getting that enzyme. For example if an individual is lactose intolerant, they can take lactase pills. Archibald Garrod's studies were so far ahead of its time, that it took decades for him to be proved correct. -
Archibald Garrod Discovers the Relationship Between Genes and Proteins
Archibald Garrod was an English physician, who discovered the relationship between genes and proteins. He came to his hypothesis, by observing inherited diseases. He believed that an inherited disease is caused due to a person's inability to make a particular enzyme. One disease he observed was a condition called alkaptonuria, in which urine appears dark red. This is caused because an individual is unable to make the enzyme to break down the alkapton. His observation is such a huge leap in -
Frederick Griffth Studies Bacterial Transformation
Frederick Griffith was an English Bacteriologist. He studied two types of bacteria, one which was lethal and one which was harmless. He injected the bacteria into mice. When he heated the lethal bacteria, it died, and became harmless. However, when the heated lethal bacteria and the harmless one were mixed, and injected it into the mice, they died. What he discovered was that some component of the lethal cells cause the change, but he did not know what the factor was. This transforming -
Fredrick Griffith (Continued)
factor was first skeptical, towards the scientific community. However, gradually, the evidence in support of DNA, increased. -
George Beadle and Edward Tatum Discover Relationship Between Genes and Enymes
George Beadle and Edward Tatum expanded on Garrod's hypothesis on the concept of genetic diseases. They studied an orange bread mold called Neurospora. They noticed that all the mutations lacked an enzyme, such as an amino acid. They were able to show that each mutant, was only defective in a single gene. They were able to come up with the one gene-one enzyme hypothesis. This stated that the function of a gene, determines the production of the enzyme. -
Erwin Chargaff Studies Relationships in DNA
Erwin Chargaff was the first to discover that the amount of DNA in a species is equal to the amount of thymine, and that the amount of guanine is equal to the amount of cytosine. This came to be a very important contribution for when Watson and Crick came to their discovery, in pairing letters. -
Alfred Hershey and Martha Chase Show the World that DNA is Heriditary Material
Using a blender, Hershey and Chase separated the protein coating from the nuclei of bacteriophages. They are the viruses that infect bacteria. They injected Nucleic Acid into the bacterial cell, and found that genes are made of Nucleic Acid DNA. Their contribution helped to convince the scientific world that DNA is heriditary material. -
Maurice Wilkins and Rosalind Franklin Find that DNA is a Helix
Maurice Wilkins and Rosalind Franklin lived in London. Using an X-Ray, Rosalind Franklin took a crystallographic photographic of DNA. This picture clearly showed that DNA's basic shape was a helix. It also revealed that it was made up of two strands of polynucleotides, which we call double helixes. Watson, without the permission of Franklin, gave the pictures to two other scientists that expanded on this topic. This discovery was crucial further the further expansions in genetics. -
James Wateson and Francis Crick Construct a Double Helix
James Watesona and Francis Crick are famous for constructing a double helix model. This conformed both to Franklin's data and to what was known at the time about DNA. It occured to Wateson that there were four bases that paired up with each other, but the question was in which way. He discovered that the As pair withe theTs, and the Gs pair with Cs. In addition, this model that was built explained many previous tests that had been performed, including Chargraff's rules. -
James Watson and Francis Crick (Continued)
This was one of the biggest leaps in all of science, as it explained the studies of previous scientists. -
Marshall Nirenberg
Marshall Nirenberg is famous for breaking down the genetic code and describing how it operates in protein synthesis. He identified the particular codons, which are a sequence of three chemical units of DNA. He learned that the RNA codon UUU specifies the amino acid phenylalanine, by adding a poly-U to a test tube mixture containing ribosomes and other ingredients. He also began to study the steps that relate DNA, RNA and protein. -
Marshall Nirenberg (Continued)
In a demonstration, he proved that messenger RNA is required for protein synthesis. Marshall Nirenberg died only last year, and his studies have been added upon. The study of genetics is a process that will never be understood fully.
