Nucleic Acids Flashcards
What is a nucleotide?
The name for the monomers of all nucleic acids.
What are nucleotides made up of?
A sugar, a phosphate group and a nitrogenous base.
What is the structure of a nucleotide?
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List and group the five bases.
Purines- adenine and guanine.
Pyrimidines- thymine, uracil cytosine.
How do the bases bond?
A purine will only bond with a pyrimidine.
Adenine only bonds to thymine or uracil.
Guanine only bonds to cytosine.
The bonds are hydrogen bonds.
Define DNA.
DNA is a polynucleotide which is double stranded in a double helix made of nucleotides containing a nitrogenous base (A,T,G,C), a deoxyribose sugar and a phosphate group.
Outline how the the hydrogen bonding between complementary bases leads to the formation of a DNA molecule.
There are two H bonds between A and T and three between G and C.
This makes the strands run anti parallel (the sugars point in opposite directions).
The fact the chains are anti parallel causes them to twist to form a double helix.
Define RNA.
RNA is a polynucleotide which is single stranded made of nucleotides containing a nitrogenous base (A,U,G,C), a ribose sugar and a phosphate group.
Outline the semi conservative replication of DNA.
The DNA is untwisted and unzipped by the enzyme helicase.
This breaks H bonds between the complementary bases.
Both strands then act as template.
Free DNA nucleotides with pair (A-T /G-C) to the template.
Hydrogen bonds reform.
The sugar-phosphate back bone is joined by DNA polymerase forming phosphodiester bonds.
Define gene.
A gene is sequence of DNA nucleotides that codes for a polypeptide.
Outline the roles of DNA and RNA in living organisms with reference to protein synthesis.
The required gene can be exposed by splitting the hydrogen bonds that hold the double helix together in that region.
RNA nucleotides form a complementary strand (mRNA). This is a copy of the DNA coding strand.
The mRNA peels away from the DNA and leaves the nucleus from the nuclear pore.
The mRNA attaches to a ribosome.
Then tRNA molecules bring amino acids to the ribosome in the correct order, according to the base sequence on the mRNA.
The amino acids are joined together by peptide bonds to give a protein with a specific tertiary structure.
What happens if there is a mutation?
If there is a mutation and the sequence of nucleotides is changed, the sequence of amino acids will be changed. This then leads to a change in the 3D structure of the protein and if it is an enzyme, the substrate will no longer fit the active site
