DNA (2) Flashcards
DNA’s discovery has been called the most important _____ work of the last 100 years.
biological
At King’s College in London in the early 1950’s, ___ ___ and ____ ____ were trying to work out the structure of DNA
Maurice Wilkins
Rosalind Franklin
What was the approach Wilkins and Franklin took?
They took an experimental approach, looking particularly at X-ray crystallography, i.e. diffraction images of DNA.
What was happening at Cavendish Institute at Cambridge University, in terms of discovering DNA?
Graduate student Francis Crick and research fellow James Watson also became interested in determining the structure of DNA. They analyzed the x-ray data collected by Rosalind Franklin and others. They then built models out of brass plates and clamps and other bits of laboratory equipment and realised that nucleic acids are arranged like a twisted ladder, with two runners made of phosphates and sugars, and a series of rungs made of pairs of organic compounds known as bases.
Elaborate Watson and Crick’s ideas about genetic replication?
Watson and Crick developed their ideas about genetic replication in a second article in Nature, published on May 30, 1953. The pairing of bases, i.e. A = T and C = G suggested that given a sequence of bases in one strand, the other strand was automatically determined. This meant when the two strands separated, each served as a template for a complimentary new chain, i.e. each strand could replicate.
After the ‘double helix’ model there were still questions about how DNA directed the synthesis of proteins. How were these questions answered?
In 1961, Francis Crick and Sydney Brenner provided genetic proof that a triplet code was used in reading genetic material in DNA and transferring this information from the nucleus to the cytoplasm via RNA to where proteins are made.
What had Crick and Brenner shown?
The two had shown that in DNA, form is function: the double-stranded molecule could both produce exact copies of itself (replicate) and carry genetic instructions, i.e. that the sequence of the bases in DNA forms a code by which genetic information can be stored and transmitted.
Who won the Nobel Prize?
Of the four DNA researchers, only Rosalind Franklin had any degrees in chemistry. She worked mostly alone and suspected, through her x-ray diffractions, that all DNA molecules were helical in structure but was reluctant to announce this finding until she had sufficient evidence. She died of cancer aged 37 years before expressing her views. In 1962, when Watson, Crick and Wilkins won 01 Franklin had died. The Nobel Prize only the Nobel Prize for physiology/medicine, living recipients and can only be shared among three winners.
Where is DNA found?
DNA is found mainly in the nucleus of a cell where it forms an important part of the chromosomes that make up the chromatin network.
What is chromatin?
chromosomal material made up of DNA, RNA and histone proteins as found in a non-dividing cell
The DNA molecule is ____ so that these long structures can fit inside the nucleus. There are nearly two meters of DNA squeezed into each human cell.
coiled
What is extranuclear DNA?
Small amounts of DNA that are found outside the nucleus in mitochondria in plants and animals and in chloroplasts in plants.
How is DNA made up?
The shape of DNA is rather like a long, twisted ladder. The two strands twist to form a stable, 3-dimensional double helix.
What units makeup DNA?
A DNA molecule is a long chain (polymer) made up of small units (monomers) i.e. building blocks called nucleotides. Each nucleotide is made up of a sugar molecule -
deoxyribose (S)
phosphate molecule (P)
nitrogenous base
What are the four nitrogenous bases?
adenine (A)
thymine (T)
guanine (G)
cytosine (C)
