Flashcards in structure of DNA and RNA Deck (27):
DNA is made from which monomer?
mononucleotides (or just nucleotides)
Name the 3 components of a nucleotide
1. phosphate group (backbone)
2. pentose sugar (backbone)
3. organic base (containing nitrogen)
Many nucleotides are known as...
In DNA the organic bases can be...
(adenine, thymine) (cytosine, guanine)
In DNA the pentose sugar is known as...
Who discovered DNA?
James Watson and Francis Crick - following pioneering work by Rosalind Franklin in x-ray crystallography - discovered DNA as double stranded (two nucleotides) helix structure, with sugar phosphate backbone and nitrogen containing organic base pairs in centre. Joined by hydrogen bonds.
What is 5' and 3'?
5 prime - the 5th carbon of the top nucleotide is nearest to the top.
3 prime - the 3rd carbon of the bottom nucleotide is nearest to the bottom.
What is a phosphodiester bond?
linkage between the 3' carbon atom of one nucleotide and the 5' carbon atom of another.
Quantities of complimentary bases are...
always the same! - however ratio varies from species to species
Describe how are 2 DNA nucleotides form a dinucleotide
a condensation reaction occurs between the hydroxyl (OH) group on the 3' carbon of Deoxyribose on 1 nucleotide and the hydroxyl group of the phosphate group on another nucleotide. (phosphodiester bond)
What is the function of RNA?
to transfer genetic information from DNA to the ribosomes.
ribosomes made from protein and another type of RNA.
another type of RNA - involved in protein synthesis.
In RNA the organic bases can be...
(adenine, uracil) (cytosine, guanine)
In RNA the pentose sugar is known as...
How many hydrogen bonds are formed between cytosine and guanine in a DNA molecule?
How many hydrogen bonds are formed between adenine and thymine in a DNA molecule?
How are the 2 strands of DNA that make up the double helix held together?
hydrogen bonds between complementary organic bases
Describe how are 2 RNA nucleotides form a dinucleotide
a condensation reaction occurs between the hydroxyl (OH) group on the 3' carbon of Ribose on 1 nucleotide and the hydroxyl group of the phosphate group on another nucleotide.
DNA is a stable molecule because...
1. the phosphodiester backbone protects the more chemically reactive organic bases inside the double helix
2. hydrogen bonds link the organic base pairs forming bridges (rungs) between the phosphodiester uprights.
3. as there are 3 hydrogen bonds between C and G, the higher the proportion of C-G pairing, the more stable the DNA molecule.
4. base stacking - additional forces between base pairs add further stability.
How is DNA adapted to carry out its function as a means of passing genetic information from generation to generation?
1. weak hydrogen bonds between base pairs - easily broken for DNA replication and protein synthesis.
2. base pairs within the helical cylinder of sugar phosphate backbone - genetic information protected to some extent from being corrupted by exterior chemical/physical forces.
3. double helix structure - makes DNA compact.
4. extremely large molecule - carries an immense amount of genetic information.
5. base pairing - leads to DNA being able to replicate and to transfer information as mRNA.
How many base pairs are in a typical mammalian cell?
approximately 3.2 billion
Function of DNA depends on...
depends on the sequence of base pairs it possesses.
What is meant by degenerate when talking about the genetic code?
more than one triplet for each amino acid.
What is meant by the term non overlapping when talking about the genetic code?
each base only read the once.
how do the organic bases help to stabilise structure of DNA?
1. Hydrogen bonds between the base pairs holds two strands together;
2. Many hydrogen bonds provides strength;
Function of DNA helicase?
break H bonds between bases.
Function of DNA polymerase?
join nucleotides together/reforrms phosphodiester backbone.