3 - NUCLEIC ACIDS Flashcards
What is a nucleotide?
A biological molecule containing a pentose sugar, phosphate group and a nitrogenous base
How do nucleotides act as monomers?
They covalently bond together by condensation to form polynucleotide chains such as DNA and RNA
What happens when nucleotides become further phosphorylated?
They form molecules such as ADP that contains 2 phosphate groups and ATP that contains 3 phosphate groups which then help regulate many metabollic pathways
Describe a DNA nucleotide.
- sugar = deoxyribose
- bases = A T C G
- number of polynucleotide strands = 2
- length of polynucleotide chain = long
- different forms = none
- location in eukaryotic cells = nucleus
Describe the structure of a DNA molecule.
Anti-parallel polynucleotide strands, one is 5’ and the other is 3’, that are twisted around eachother forming a double helix shape
What are the names of the 4 organic bases and how do they pair up?
A = adenine pairs with T = thymine C = cytosine pairs with G = guanine
What type of bond forms is found between these base pairs?
Hydrogen bonds - 3 between cytosine and guanine and 2 between adenine and thymine
What is this process called and why is it important?
Complemetary base pairing; it allows DNA to be replicated without error and reduces the occurence of mutation
What are purine bases?
Bases with 2 rings such as adenine and guanine
What are pyrimidine bases?
Based with 1 ring such as thymine, U = uracil and cytosine
What role does the pairing of purine and pyrimidine bases play in the structure of DNA?
Equal sized rungs are formed between the rings which enable the strands to twist around eachother into the double helix, giving stability
What is a phosphodiester bond?
Covalent bond formed by condensation between:
- the sugar and the phosphate group in a nucleotide
- nucleotide monomers in DNA strands
What is the importance of the sugar-phosphate backbone?
It maintains the molecule’s stability and ensures that the integrity of the coded information within the base sequences is protected
When is DNA replicated? Why?
During the synthesis stage of the cell cycle, in order to make new cells for growth and repair (mitosis) and to make sex cells/ gametes (meiosis)
What is the first step in DNA replication?
DNA helicase, which breaks hydrogen bonds between bases in a parent DNA molecule and unwinds the strands so they act as templates
What is the second stage of DNA replication?
Free nucleotides with complementary bases are attracted to the exposed bases and DNA polymerase forms hydrogen bonds between them
What is the third stage of DNA replication?
DNA polymerase and DNA ligase join nucleotides to form the new strand by phosphodiester bonds and reform the sugar-phosphate backbone
Why is this process known as semi-conservative replication?
Because it results in 2 new strands, each containing one parent strand from the original DNA molecule
Describe an RNA nucleotide.
- sugar = ribose
- bases = A U C G
- number of polynucleotide strands = 1
- length of polynucleotide chain = short
- different forms: (3) messenger, transfer and ribosomal
- location in eukaryotic cells = nucleolus
What is a gene and what is its role?
It is a section of a DNA molecule which provides the sequence of bases which determines the sequence of amino acids and thus a protein
What is a base triplet?
A triplet of bases on a DNA molecule
What is a codon?
A triplet of bases on a length of an mRNA molecule
What is an anti-codon?
A triplet of bases on a tRNA molecule that is complementary to the codon of mRNA
What does a tRNA molecule carry?
A base triplet attached to an amino acid on one end and an anticodon on another end
