Nucleic Acid Structure and DNA - Lecture 5 Flashcards
What is Translation?
Conversion from DNA to messenger RNA
What is Transcription?
Conversion of RNA to Protein
What is a Nucleoside?
It is a Nucleotide without the Phosphate group
Consists of Base and Sugar
What is a Nucleotide composed of?
Phosphate
Sugar
Nitrogenous Base
What is the sugar used in DNA?
Deoxyribose
What is the sugar used in RNA?
Ribose
What are the Purines?
Adenine
Guanine
What are the Pyrimidines?
Uracil
Thyamine
Cytosine
How is a ncleotide added into a chain?
Hydrogen bond first forms between bases
phosphodiester bond occurs between a free 3’ OH group and a 5’ Triphosphate
Phosphdiester bond causes a loss of 2 Phosphates
What is the 5’ end of DNA?
Strand from 5’ to 3’
It is the end of DNA that begins with an OH group on the 3’rd carbon
Ends with Phosphate group on the 5’th carbon
What is the 3’ end of DNA?
Strand from 3’ to 5’
It is the end of DNA that starts with the phosphate group on 5’th carbon
Ends with the OH group on the 3’rd carbon
What is the “Central Dogma” of DNA?
DNA in each cell constitutes the genome which carries the genetic information required for making an
organism
Describe the DNA double helix
One 5' to 3' On to 3' to 5' They are anitparallel strands A with T G with C
How many hydrogen bonds are there between Adenine and Thyamine?
Two Hydrogen Bonds
How many hydrogen bonds are there between Cytosine and Guanine?
Three Hydrogen Bonds
What direct can nucleotides only be added?
Only added from the 3’ end
What catalyses DNA replication?
DNA polymerase
How does DNA Polymerase operate?
Can only add to existing nucleic acids
Can not start DNA synthesis on their own
Requires an RNA primer to start replication.
How does Replication of DNA begin?
DNA helicase binds and unwinds the DNA
What are the two strands in DNA termed?
Leading Strand
Lagging Strand
Which strand in DNA replication is the leading Strand ?
3’ to 5’ strand
Which strand in DNA replication is the lagging strand?
5’ to 3’ end
How must the lagging strand be replicated?
By use small okazaki fragments
Describe the sequence of DNA replication?
DNA helicase unwinds the strands
RNA primers synthesise and bind to the unwound DNA
Nucleotides are added from the 3’ end
DNA polymerase catalyses the reaction
The lagging strand contains RNA sequences from the Okazaki - These are removed post synthesis
DNA polymerase fills in the gaps of the Okazaki fragments
How is the RNA primer synthesised?
Via the use of Primase
What acts as a proof reader for DNA?
DNA polymerase has 3’ to 5’ exonuclease activity (acts as a proof reader)
