Unit 2 - Nucleic acids & DNA replication Flashcards
What does DNA stand for?
Deoxyribonucleic acid
What does RNA stand for?
ribonucleic acid
What is the monomeric unit for nucleic acids?
Nucleotides
What are the 3 components of a nucleotide?
- phosphate group
- pentose (5 carbon sugar) either deoxyribose or ribose
- nitrogenous base
Name the 5 nitrogenous bases
- thymine
- guanine
- adenine
- cytosine
- uracil
Name the 4 bases present in DNA
- thymine
- adenine
- guanine
- cytosine
Name the 4 bases present in RNA
- uracil
- adenine
- guanine
- cytosine
Which base is never found in DNA?
Uracil
Which base is never found in RNA?
Thymine
How are polynucleotides formed?
- condensation reactions occur
- between the phosphate on carbon 5 of one nucleotide and the hydroxyl group on carbon 3 of another nucleotide
- water is released
- phosphodiester bond formed
What sort of bond is formed between nucleotides?
Phosphodiester
How are sequences of RNA/DNA given?
From the 5’ end to 3’ end
What are the two types of bases?
Purines and pyrimidines
What is the structure of purines?
Double ringed
What is the structure of pyrimidines?
Single ringed
Which bases are purines?
Adenine and guanine
Which bases are pyrimidines?
Cytosine, thymine, and uracil
What does complementary base pairing allow?
-DNA to be copied and transcribed
What type of bonds hold bases together?
Hydrogen bonds
How many hydrogen bonds form between Adenine and Uracil/Thymine?
2
How many hydrogen bonds form between Guanine and Cytosine?
3
In order to allow for the bases to form hydrogen bonds what must happen to one of the polynucleotide chains?
It must be rotated through 180 degrees
How does the sugar phosphate backbone run on one of the polynucleotide chains? How does the other polynucleotide chain run? What is this called?
From 5’ to 3’ and the other from 3’ to 5’
The antiparallel nature of DNA
Describe the steps involved in extracting DNA
- sample ground up using pestle and mortar
- sample mixed with detergent
- salt is added
- protease is added
- ice cold ethanol is added down the side of the test tube
Why is the sample ground in the extraction of DNA?
it breaks down the cell walls
Why is detergent added to the sample in the extraction of DNA?
breaks down the cell membrane, releasing the cell contents into solution
Why is salt added to the sample in the extraction of DNA?
neutralises charges on phosphates in sugar phosphate backbone
breaks the hydrogen bonds between DNA and water
makes DNA less soluble
Why is protease added to the sample in the extraction of DNA?
breaks down the proteins associated with DNA
Why is ethanol added to the sample in the extraction of DNA?
Causes the DNA to form a white precipitate between the layer of the sample and the ethanol