Lesson 1: Molecular Genetics Flashcards
Describe how the research of Oswald Avery was built upon the discoveries of at least two other researchers before him.
1) Miescher``s discovery of nuclein spurred other scientists to investigate the chemical nature of the DNA molecule, in the early 1900s
2) Griffith found what he called a transforming principle which led to genetic information being passed between bacteria
Explain how the results from the Hershey and Chase experiment proved that DNA alone is responsible for passing on hereditary information.
The locations of the radioactively labelled DNA and protein from the phage virus were tracked after the virus infected the bacterial cell. Only the labelled DNA - not the protein - was found inside the bacteria, proving that DNA alone is sufficient and responsible for passing on the hereditary material needed to make new virus particles.
Explain how the Watson and Crick model of DNA structure explained the earlier discoveries of Chargaff and Franklin.
The Watson and Crick model showed that the DNA molecule is a twisted helix with two sides running anti-parallel to each other. This matched the images of a helical model that Franklin took, using X-ray crystallography. The Watson and Crick model also revealed complementary base pairing (A binds to T, and G binds to C.) This matched Chargaffs experiments, which showed that the proportions of adenine and thymine are equal to each other, but are not necessarily equal to the proportions of guanine and cytosine.
Describe an unplanned or chance event that led to a major discovery in the history of early DNA research.
1) Griffith discovering that the combination of two non-lethal strains of bacteria could produce a fatal case of pneumonia in the mice
2) James Watson being allowed to see Rosalind Franklins unpublished x-ray crystallography results, enabling him to realize which of his own models was probably right
Nucleotide Structure
- nucleotides consist of a nitrogen base, a five carbon sugar (deoxyribose) and a phosphate group
- The sugar and phosphate are the same in every nucleotide, but there are four different types of nitrogen bases. A,G,C,T.
- Adenine and guanine have a double structure and they are called purines
- Cytosine and thymine have a single ring structure and are called pyrimidines
Why can purines and pyrimidines only bond to each other and not to themselves?
(only purine to pyrimidine is possible)
- purines can only bond to pyrimidines
- pyrimidine to pyrimidine pairings are not possible because the molecules are too far apart for hydrogen bonding to be established
- purine to purine pairings are not possible because the molecules are too close leading to overlap repulsion
- The only possible pairings are A with T and G with C (the only two with matched donors and acceptors)
Bonds in bases
- AT pairing is joined by a double hydrogen bond and the GC pairing is joined by a triple hydrogen bond.
What is cmplementary base pairing
In DNA, adenine only pairs up with thymine and guanine only pairs up with cytosine.
From nucelotides to DNA
The nucleotides attach to each other by connecting the sugar group of one nucleotide to the phosphate group of the next. The desoxyribose and phosphate molecules are joined together by a covalent bond called a phosphodiester bond. It is the sugar-phosphate linkage that forms the backbone of the DNA molecule.
How to label 5 prime and 3 prime
The 5 prime carbon has a phosphate group attached to it and the 3 prime carbon has a hydroxyl group attached (OH) group
Describe two examples where a research scientists or geneticist needs good oral or written communication skills in their work with colleagues or the public.
Geneticist:
- takes student groups around
- works with other scientists on their genetics projects
Biologist:
- writes books and info for cds, books, maps
- writes scientific papers for journals
What is systematic biology?
It is a field of biology involved with the comparative study of genetic sequences and their evolution across groups of organisms. Systematic biologists study the evolution of biodiversity.
Why would you have to mash a strawberry before adding the lysis solution?
To break up the cell walls of the tissues to help release the DNA
What did the lysis solution do in the extraction process?
The lysis mixture chemically broke up the cell and nuclear membranes to release the DNA into solution
What is DNA?
is a double-stranded, helical molecule. It consists of two sugar-phosphate backbones on the outside, held together by hydrogen bonds between pairs of nitrogenous bases on the inside.
