Nucleic acids and chromosomes NAGE 1 Flashcards
What is the difference between a nucleotide and a nucleoside?
A nucleotide has a pentose sugar, a phosphate and a nitrogenous base, whereas a nucleoside has a pentose sugar and a base. Nucleosides does not refer to the phosphate groups.
In a nucleotide, which carbon on the pentose is the phosphate bonded to and which carbon is the base bonded to?
The phosphate group is attached to the carbon at position 1 and the phosphate is attached to the base at position 5.
What is the structural difference between ribose and deoxyribose?
Deoxyribose has one less oxygen atom in the molecule. On carbon 2, an hydroxyl group will be found on ribose, but only a hydrogen is found in deoxyribose.
N.B. This cannot be found on carbon 3 because the hydroxyl group is needed for the condensation reaction between nucleotides to form phosphodiester bonds.
Name the bases found in DNA and the base found in RNA
DNA: Adenine, Guanine, Cytosine, Thymine
RNA: Adenine, Guanine, Cytosine, Uracil
Identify which of the bases found in polynucleotides are purines and which are pyrimidines.
Purines: Adenine and Guanine ( AG )
Pyrimidines: Cytosine, Uracil and Thymine ( CUT )
What direction is DNA conventionally written in?
From the 5’ to the 3’ direction
Which group from DNA is found on the 5’ end and which group from DNA is found on the 3’ end?
At the 5’ end is the phosphate group and at the 3’ end is the hydroxyl group which can be used in a condensation reaction to elongate DNA.
Describe the structure of a single DNA molecule
Two strands of DNA are joined together by hydrogen bonds. DNA is 2nm thick. 10bp makes 1 helical twist.
What is the difference between the major and minor groove?
The major groove is where the backbones are far apart, and the minor groove is where the backbone are closer together. The grooves twist about the molecule on opposite sides. In the major groove, the Nitrogen and Oxygen atoms not he base pairs are pointing inwards towards the helix. In the minor groove, the Nitrogen and Oxygen is pointed outwards. Binding to.
Why are proteins and transcription factors more likely to bind onto the major groove than the minor groove?
Binding to the minor site is energetically unfavourable.
What are Watson-Crick base pairs?
This is the base pairing in DNA. Adenine binds to thymine with two hydrogen bonds and Guanine binds to Cytosine with three hydrogen bonds
How can we melt/denature DNA?
Low salt concentration
High temperatures
How can we re-anneal / hybridise DNA?
Low temperature/ high salt concentration
Why does Low Salt concentration denature DNA?
DNA in a polyanionic compound due to the phosphate background. Cations shield the negatively charged phosphates, eliminating the repulsive force between the two anti parallel strands.
If stretched out, how long is the E.Coli genome and how long is the Human genome in one cell
The E.Coli Genome will be 1.4mm and the human DNA will be 2 metres
