Discovery of DNA

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03/02/2023

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20 Terms

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Pre-discovery of DNA
* Charles Darwin understood variability within living beings is the driving force of the evolutionary process
* Gregor Mendel studied and described inheritable features of pea planta
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Johann Friedrich Miescher
* 1869
* Isolated new substance from pus
* Substance was derived from cell nuclei - therefore, nuclein
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Richard Altmann
* 1889
* Nucleic has an acidic component
* Coined ‘nucleic acid’
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Albrecht Kossel
* 1893
* Determined that nucleic contained four bases
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Phoebus Levene
* Discovered nucleic acid is made of three basic components:
* A sugar
* An acid
* An organic base
* Characterised different types of nucleic acid, DNA, and RNA
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Transforming Principle
* Frederick Griffith in 1928
* A molecular factor presented in smooth bacterial strain could transform nonvirulent bacteria into virulent ones
* Avery, MacLeod, and McCarty established it’s DNA in 1944
* Discovered by treating these experiments with protein enzymes and DNase
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Alfred Hershey and Martha Chase
* 1952
* Worked with bacteriophage
* Injected the DNA into host cell
* Labelled proteins with a radioactive isotope of sulphur
* When it infected cells, it’s seen no radioactivity enters the cell
* Instead, they found phosphorous (found in DNA)
* Discover DNA is genetic material
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Chargaff’s Rule
* 1950s
* Base composition of DNA varies between species
* DNA specimens isolated from different tissues of the same species have the same base composition
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Bases
* No. of adenosine residues = no. of thymine residues (A = T)
* No. of guanine residues = no. of cystine residues (G = C)
* Sum of purine residues = sum of pyrimidine residues
* A + G = T + C
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Rosalind Franklin
* 1952
* Used X-ray diffraction to determine DNA shape
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Rosalind Franklin Conclusions
* DNA has a helical shape
* Nitrogenous bases were on the inside
* Sugar-phosphate backbone on the outside
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Watson and Crick
* 1953
* Built a model of double helix DNA moleculeW
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Watson and Crick Conclusions
* Thymine and adenine pair to each other with 2 hydrogen bonds
* Cytosine and guanine pair to each other by 3 hydrogen bonds
* DNA strands are antiparallel
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Nirenberg and Matthaei
* 1961
* Cracked genetic code
* Made base of RNA (homopolymers of uracil)
* Added homopolymer to a cell freeze suspension
* Analysed protein product
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Nirenberg and Matthaei Conclusions
* All 20 amino acids were in the mixture at first
* At the end, it was just phenylalanine
* Determined code of phenylalanine involved the base U
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φX174
* 1977
* Fredrick Sanger
* First DNA genome sequence
* φX174 is a bacteriophage
* It has single-stranded DNA as its genetic material
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Human Genome Project
Determined the sequence of nucleotides in the DNA of a human genome
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Genome
The collection of DNA molecules that’s characteristic of an organism
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Genomics
* The analysis of DNA sequences that make up a genome
* Involves DNA sequencing technology, robotics, and computer science
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DNA Sequence
* Contains the instructions for its own replication and synthesis of specific proteins
* Determines the structural and functional traits of an organism