Nucleotides Flashcards
What is a nucleotide made off?
A pentose sugar
A nitrogenous base
A phosphate group
They contain C,H,O,N,P
Nucleotide bonding
They join between the phosphate group of one nucleotide and the sugar of another creating a sugar phosphate back bone
- Phosphodiester bond created via condensation reaction
How is a double helix created?
- Two DNA polynucleotide strands join together at the complementary base pairings.
- Purine always bonds with a pyrimidine 2 hydrogen bonds between A and T and 3 between G and C
- Two antiparallel strands twist and form a dna double-helix.
Self replication
- DNA helicase breaks the hydrogen bonds between the two polynucleotide strands
- Each original strand acts a template for new strand free floating nucleotides join to the exposed bases on each strand by complementary base pairing
- Nucleotides of new strand joined together by DNA polymerase forming sugar phosphate backbone hydrogen bonds form again.
MRNA
- Made in the nucleus
- Three adjacent bases called a codon
- Carries genetic info from dna in the nucleus to the cytoplasm where its used to make proteins during transcription
tRNA
Found in cytoplasm
Has a binding site for amino acids at one end and a sequence of 3 bases at the other end called an anticodon
Carries amino acids that are used to make proteins to the ribosomes during translation.
rRNA
Forms two units in a ribosome
Ribosome move along the mRNA strand during protein synthesis- rRNA helps catalyse the formation of peptide bonds between the amino acids.
Non-overlapping codons
Codons are read in a sequence of threes so base triplets don’t share base pairing
Degenerate
More possible combinations of triplets than amino acids some amino acids are coded by more then one base triplet
Universal codon
This means every codon codes for the same amino acids in every living organism
