DNA Flashcards
Why is DNA a polynucleotide ?
It is composed of many nucleotides.
What are the main components of DNA.
2 sugar phosphate backbones held together by base pairs.
What are the 4 types of nitrogenous base pairs ?
Adenine
Thymine
Guanine
Cytosine
Which nitrogenous bases pair together.
A and T
C and G
How many hydrogen bonds do each set of nitrogenous bases create ?
A to T = 2 hydrogen bonds
C to G = 3 hydrogen bonds
What are the monomers of DNA called.
Nucleotides
What are nucleotides.
Monomers of DNA
How are nucleotides formed
Condensation reactions where water is removed and replaced by a phosphodiester bond which is created between the sugar and the phosphate in the sugar-phosphate backbone.
What is the bond between the ribose sugar and phosphate in DNA called.
Phosphodiester bond
What does a phosphodiester bond join ?
Ribose sugar and phosphate
Which molecules loose what during the formation of a phosphodiester bond ?
Ribose sugar looses OH
Phosphate looses H
What type of bond is created between the sugar and the nitrogenous base in DNA.
Covalent bond
Where is a covalent bond created in DNA
Between the sugar and the nitrogenous base.
What are the 3 types of bond in DNA and what are they between ?
Hydrogen between nitrogenous bases.
Phosphodiester between sugar and phosphate
Covalent between sugar and base
What is the final shape of DNA
Helix due to it twisting
Which nitrogenous bases are purines ?
Adenine and guanine
Which nitrogenous bases are pyrimidine
Thymine and cytosine
What does purine relate to and what does it mean.
Both adenine and guanine nitrogenous bases are purine as they have double ring shapes.
What does pyrimidine mean and what does it relate to ?
Both thymine and cytosine and pyrimidine was they have only single ring shapes.
Why are DNA strands anti parallel.
The DNA strand are anti parallel as one strand runs from carbon 3 to carbon 5. Whilst the other runs from carbon 5 to carbon 3.
What functions of DNA give it the ability to carry out its function ?
Coiling makes it compact
Sugar to phosphate backbone gives strength
Long molecules store a lot of information
Complementary base pairing enables information to be replicated
Double helix protects hydrogen bonds and makes the molecule stronger
Many hydrogen bonds create stability and prevent code corruption
Hydrogen bonding allows chain to split for replication.
Describe in detail how DNA is replicated.
- DNA helicase unwinds the DNA and breaks the hydrogen bonds.
- The two strands of DNA separate and are stabilised by binding proteins.
- Free nucleotides approach the exposed bases of both strand. The complementary base pairs form hydrogen bonds.
- DNA polymerase joins the new nucleotides together by condensation reactions to form a new strand.
- Each new molecule is an exact copy of the original. With one old parent strand and one newly-synthesised daughter strand.
- The molecule twists into a helix.
- This is semi-conservative replication.
Why is DNA replication known as semi-conservative ?
When DNA replicated one strand of each molecule is the old parent strand and one is the newly-synthesised daughter strand.
Half remains
