Nucleic acids Flashcards
Structure of nucleotide
- pentose sugar (5 carbons), a phosphate group and a nitrogen containing organic base.
- joined together by condensation reaction
- bases either A,T,C,G OR U
Describe the structure of RNA
- single stranded, relatively short polymer of nucleotides joined by phosphodiester bonds.
- pentose sugar is always a ribose sugar
- bases = G,C, A, U
Describe DNA structure
- polymer of nucleotides joined by phosphodiester bonds
- pentose sugar is deoxyribose
- organic bases = A,T,G ,C
-Made up of 2 strands of nucleotides (polynucleotides). Each of the 2 strands is very long and are joined together by H bonds formed between bases
-double strand twists into a double helix
Describe the events which take place during DNA replication.
1.Strands separate / H-bonds break
2.DNA helicase (involved)
3.Each strand acts as ) template
4.Free nucleotides attach;
5. Complementary base pairing
6.DNA polymerase joins nucleotides
7.H-bonds reform
8. Semi-conservative replication
name the type of reaction that joins two nucleotides together.
condensation reaction
state the location of the new chemical bond that is formed when two nucleotides are joined together.
between the phosphate group of one nucleotide and the sugar of another
name the bond formed when two nucleotides are joined together.
phosphodiester bond
the chain for sugar and phosphates in a polynucleotide is collectively known as what?
sugar-phosphate backbone
what is the advantage of DNA being a helix shape?
DNA is a very long molecule, the helix shape (twisting) allows a lot of genetic information to be stored in a small space - nucleus
the two polynucleotide strands in a DNA molecule are antiparallel. what does this mean?
they run in opposite directions.
if in a section of DNA, 33% of the bases were A, what % of the bases are T? explain your answer
33% are T because number of A is equal to the number of T
if in a section of DNA 33% of the bases were A, what % of the bases are G?
A=T, so 33+33 = 66% of base are A&T. 100-66=34. so 34% of the bases are G and C. so %G = 34/2 = 17%
what is the role of DNA helicase in DNA replication?
breaks the hydrogen bonds between bases causing the strands to separate.
what happens once the DNA double helix has separated into two separate strands?
each strand acts as a template strand. free floating DNA nucleotides match up using complementary base pairing.
What is the role of DNA polymerase?
to catalyse the joining together of adjacent nucleotides on the new strand by condensation reactions, resulting in the formation of a phosphodiester bond.
why is DNA polymerase only complementary to the 3’ end of a DNA strand?
DNA polymerase is an enzyme. enzymes are specific to one substrate. DNA polymerase has an active site with a specific shape that is only complementary in shape to the 3’ end of a DNA strand.
Events that take place during DNA replication
-unwinding of DNA’s double helix structure through DNA helices breaking H bonds between base pairs
-free nucleotides bind to complementary bases
-DNA polymerase builds the polynucleotide by forming phosphodiester bonds by a condensation reaction
Describe the formation of a new polynucleotide strand.
A new polynucleotide strand is formed when DNA polymerase forms phosphodiester bonds between the phosphate on one nucleotide and the sugar on another
How is DNA adapted to carry out it’s functions
-Stable due to many H bonds between bases and these being protected by sugar phosphate backbone
-H bonds between strands > easy to seperate from replication molecule
- large molecule > carry huge amount of info
-base pairing > DNA can transfer information as RNA
Describe complementary base pairing
- Adenine always pairs with thymine
- Guanine always pairs with cytosine
- H bonds between the bases
- 3 H bonds between C and G/2 H bonds between A and T
Explain semi-conservative process of DNA replication
-DNA helices breaks H bonds between base pairs, causing double helix structure to unwind
-free nucleotides bind to complementary bases on the exposed polynucleotide
-DNA polymerase builds up the polynucleotide by forming phosphodiester bonds (condensation reaction)
-2 new polynucleotide chains are formed. Each strand has half the original genetic material
Explain the semi conservative process of DNA replication.
DNA replication is semi conservative because each of the new strands contains one of the original strands
Explain why the process of DNA replication is described as semi-conservative
replicated DNA has 1 original strand and 1 new strand
If and inhibitor of DNA polymerase were introduced into a cell, explain what the effect would be on DNA replication
-regardless on type of inhibitor, enzyme substrate complex wouldn’t form
-so condensation reaction needed to bind nucleotides together wouldn’t occur
-so DNA replication wouldn’t happen
