Nucleic Acids Flashcards
What is the role of DNA?
To store genetic information for growth and development
What is the monomer of DNA?
And what is it made of?
Nucleotide
Made of a nitrogenous pass
Deoxyribose sugar
Phosphate group
What bonds form between nucleotides :
1. In the backbone
2. Between nitrogenous base (with which complementary pairs make what?)
Phosphodiester bonds
Hydrogen bonds, adenosine and thymine = 3 guanine and cytosine = 2
What is the structure of DNA?
Double stranded helical structure
Sugar-phosphate backbone joined by phosphodiester bonds
Complementary base pairs joined by hydrogen bonds to hold two strands together
What is the function of RNA?
To store and transport genetic information
What is the name and structure of a monomer of RNA?
Nucleotide made of nitrogenous base, ribose sugar, phosphate group
What are the four nitrogenous bases of DNA and which what is the fifth nucleotide and what does it replace?
Adenine, guanine, Thymine, Cytosine.
Uracil replaces Thymine
Which nitrogenous bases are purines and which are pyrimidines?
Purines: adenine and guanine
Pyrimidines: Uracil, Thymine and Guanine
What is it called where one strand of dna is at 180 degrees to the other stand
Anti parallel strands
Which strand is “upside down”
3’ to 5’ strand
What rule allows us to work out the percentage of specific bases in DNA?
Complementary bases are in a 1:1 ratio.
Why was it first doubted that DNA could carry enough genetic code for organisms?
It only had four bases they questioned why something so simple could create such variance
They believed that it was more likely a protein
What is it called when we use three bases to code for one amino acid?
And what term is used to explain why it’s so good?
Triplet code
It’s universal and degenerate
Who confirmed the double helix structure?
Watson and Crick
What method is DNA replicated by
Semi-conservative replication
What are the enzymes involved in semi conservative replication and what is their function?
DNA gyrase - unwinds DNA
DNA helicase - unzips DNA
DNA polymerase - forms sugar phosphate backbone
DNA loaves - joins segments on the lagging strand together
Where does DNA bind and act?
At the replication fork
What is the proses of semi-conservative replication?
- DNA is unwound and unzipped by enzymes gyrase and helicase
- Free nucleotides pair up along complementary base pairs.
- DNA polymerase catalyses condensation reactions between sugar and phosphate groups. - this works in 5’-3’ direction so it works in sections on the 5’ to 3’ strands.
- DNA Ligase joins segments on the lagging strand together
What were the three theories of DNA replication? And what strands did they produce?
Conservative. 1. Parent-parent 2. New-new
Semi- conservative 1.parent-new 2. Parent-new
Dispersive - mixture of old and new strands
Who proved the semi conservative model?
Meselsohn and Stahl
What was the process of the nitrogen experiment that proved semi conservative replication?
- E.Coli grown in mediums of 14N and 15N (known isotopes)
- Mixed with calcium chloride so DNA leaks out. Then is spin in a centrifuge
- Gen1. Grown in 15N
Gen2. Transferred to 14N
Gen 3 kept in 24N
What is the method for extracting DNA from fruit?
Mash fruit
Add water
Add salt solution, detergent solution, protease solution
Invert test tube
Heat gently in water bath
Add ice-cold ethanol
DNA precipitates out
