Structure of RNA and DNA Flashcards
(20 cards)
Function of DNA
Used to store genetic information, all the instructions needed to grow and develop from a fertilised egg to a fully grown adult.
Function of RNA
One of the main functions is to transfer genetic information from the DNA to ribosomes.
What are the 3 components of a nucleotide?
Pentose sugar, nitrogen-containing sugar organic base and a phosphate group.
What is the sugar in DNA called?
Deoxyribose.
What are the 4 bases of DNA?
Adenine (A), thymine (T), cytosine (C) and guanine (G).
What is the sugar in RNA called?
Ribose.
What are the 4 bases in RNA?
Adenine (A), Uracil (U), cytosine (C) and guanine (G).
What is a polynucleotide? How are they formed? What is the bond formed by condensation reactions?
A polymer of nucleotides. They join up between the phosphate group of one nucleotide and the sugar of another. The bond formed is a phosphodiester bond.
Wat is a chain of sugars and phosphates known as?
The sugar-phosphate backbone.
How are two DNA strands joined together?
By hydrogen bonds between bases C and G or A and T due to complementary base pairings.
How many hydrogen bonds form between the DNA bases?
A&T-2
C&G-3
How are the two strands of a DNA molecule described?
Two antiparallel polynucleotide strands twisted to form a double-helix.
Watson and Crick
They worked out the structure of DNA by looking at X-rays of the diffraction patterns of DNA.
How does the structure of RNA differ from DNA?
It is made from a single strand of polynucleotide and is much shorter than most DNA strands. It contains base U instead of T.
What is a purine and which bases are purines?
Composed of 2 carbon rings, A and G.
What is a pyrimidine and which bases are pyrimidines?
Composed of 1 carbon ring, U, T and C.
How and why is DNA stable?
The phosphodiester backbone protects the more chemically reactive bases inside. It is relatively stable as a molecule as it passes from generation to generation, only rarely with any changes.
How is DNA adapted to its function?
- It’s stable so mutations happen rarely
- The 2 strands can separate allowing DNA replication
- The base pairings are protected inside the helix
- The base pairings of DNA lead to RNA being able to transfer information.
Which carbon is which in a nucleotide?
3’ has a hydroxyl group and 5’ is attached to the phosphate.
Why can nucleotides only be synthesised in the 5’-3’ direction?
The enzyme DNA polymerase (the enzyme that assembles nucleotides into a DNA molecule) can only attached nucleotides to the hydroxyl group of the 3’ carbon as the active site is complementary to this end.
