Nucleotides and Nucleic Acids Flashcards
What are the monomers from which DNA and RNA are made from?
nucleotides
What are the components of the nucleotide structure?
- a pentose sugar
- a nitrogen-containing organic base
- a phosphate group
Which bases are purines?
adenine and guanine
Which bases are pyrimidines?
cytosine, thymine and uracil
What is the structural difference between purines and pyrimidines?
purines have a double ring structure - pyrimidines have a single ring structure
Do both DNA and RNA have a pentose sugar?
yes - DNA is a deoxyribose and RNA is a ribose
What is the difference in bases for DNA and RNA?
DNA contains thymine and RNA contains uracil
What is the difference in number of strands of DNA and RNA?
DNA - double-stranded (double helix)
RNA - single-stranded
Outline the role of RNA polymerase in the production of the mRNA sequence.
- joins/adds RNA nucleotides
- forms phosphodiester bonds (between nucleotides)
What direction does DNA polymerase only work?
5’ to 3’
What is the method to extract DNA from fruit?
1, Mash the fruit and mix this into a beaker containing solution of detergent (the detergent breaks down the cell membranes and the nuclear membranes, causing the fruit cells to release their DNA) and salt (the salt causes the DNA to stick together)
2, Filter the mixture into a test tube (this removes any debris - big, insoluble bits of cell - from this mixture)
3, Add protease (to degrade histones/DNA-associated proteins and other cellular proteins)
4, Gently add some ice-cold ethanol to the filtrate (the filtered mixture) by pouring the ethanol slowly down the side of the test tube (this causes the DNA to precipitate i.e. come out of the solution as DNA is not soluble in cold alcohol)
5, The DNA will appear as a stringy white precipitate (solid) and if needed this precipitate can be carefully extracted using a glass rod.
When extracting DNA, why might you need to crush/grind the sample?
- to break open cell walls!
- if the sample is a tissue, to separate into individual cells
What enzyme should be added when extracting DNA and why?
- protease
- to break down histones/proteins associated with DNA
What process occurs when a white layer of DNA forms between the sample and the ethanol?
precipitation
Why, in DNA extraction, is ice-cold ethanol used?
It reduces enzyme activity e.g. inhibit the activity of some enzymes that may break down DNA
