Nucleic Acids Flashcards
Nucleotides structure
What’s it made up of?
Pentose sugar
Phosphate group PO42-
Nitrogenous base
Nucleotide (monomer) -> polynucleotide (polymer)
What’s an example of a polynucleotide
Nucleic acids: these are long chains of nucleotides with phosphodiester bonds between them
Where does the phosphodiester covalent bond form between in groups of adjacent nucleotides
5’ Phosphate group to 3’ hydroxyl group
Forms sugar phosphate backbone
This is formed by condensation
Examples of nucleic acids
DNA & RNA
DNA VS RNA
(helical, any extra forms, strands, pentose sugar present, bases present?)
Purine vs pyramidine bases - how many rings
Purine - 2 carbon rings (larger bases)
Pyramidine - 1 carbon ring (smaller)
Examples of pyramidines
Cytosine & Thymine
Purine bases
Adenine & guanine
Adenine -> Thymine how many H bonds
2 hydrogen bonds
Cytosine -> Guanine how many H bonds
3 Hydrogen bonds
Why is complementary base pairing key?
- DNA can be replicated without error
- same sequence of nucleotides produced = accurate
- reduces occurrence of spontaneous, random mutations
- allows formation of H bonds
Example of phosphorylated nucleotides
ADP & ATP
Nucleotides with more than one phosphate group
ADP & ATP similarity & difference
ADP = 2 phosphate groups
ATP = 3 phosphate groups
-> both contain a pentose sugar (ribose), a nitrogen base (adenine) & inorganic phosphates
What is semi-conservative DNA replication
Each strand acting as a template strand, with each new DNA molecule formed has 1 old strand and 1 new one of DNA
Steps of DNA replication
- DNA unwinded by gyrase
- DNA helicase unzips the DNA molecule, breaking the hydrogen bonds & separating the 2 strands
- DNA polymerase forms phosphodiester bonds, joining adjacent free nucleotides together
- C&G bind (3H), A&T bind (2H)
- The sugar phosphate backbone forms by phosphodiester bonds
How does the structure of DNA allow replication
Purines only bind with pyramidine
Complementary base pairings (C&G, A&T)
Double stranded
H bonds between complementary bases
Each strand acts a template
The nature of genetic code traits
- universal (all living organisms use the genetic code: the same triplet = same amino acid in all organisms)
- degenerate (several codons / triplets code for the same amino acid; mutation may be silent, not changing the amino acid coded for)
- non overlapping (each base only ready as part of one codon)
Read as a triplet = each codon only codes for an amino acid
What does the nature of the genetic code allow to happen
Genetic engineering and transferable info between species
Transcription steps
- DNA is copied into mRNA
- Free RNA nucleotides line up by complementary base pairing to the template DNA strand, catalysed by RNA polymerase
- mRNA carries a copy of the gene code out of the nucleus to ribosomes for protein synthesis
Steps of translation
- mRNA moves to the ribosome
- tRNA anticodon binds to mRNA codon
- tRNA brings specific amino acid
- Peptide bond forms between adjacent amino acids
Transcription (& translation) VS Dna Replication
Transcription (& translation) VS Dna Replication
