Genetic code and protein synthesis Flashcards
What is a gene?
Section of DNA that contains a specific nucleotides base sequence.
Encodes for Sequencing amino acids during protein synthesis (translation) determining the tertiary structure of a single polypeptide and Functional RNA (mRNA, tRNA, rRNA)
Position of each gene along a chromosome is a ‘gene locus’.
What are the features of the genetic code?
20 different amino acids exist
Each amino acid has its own code of DNA bases
4 different bases (A,T, C and G)
Triplet code of 4x4x4 bases = 64 triplets (codons)
Each triplet (codon) encodes for one specific amino acid
Degenerate - amino acids can have more than one codon
Non-overlapping - each base is only read once (123, 456, 789)
Universal - each codon codes for the same amino acid in all organisms
What is a genome
Genome is the complete set of genes in a cell, including any mitochondrial / chloroplast genes.
What is a proteome
Proteome - full range of proteins produced by the genome.
Cell proteome - proteins produced by a specific cell as a result of which genes are switched on / off.
Detail the process of transcription (DNA to mRNA).
An enzyme starts to unwind and separate the DNA strands at the start of a gene.
This exposes the nucleotide bases on in the strands including the template (coding) strand.
Free, activated RNA nucleotides undergo complementary base pairing, through hydrogen bonding, with the bases on the template strand only.
A to T, U to A, C to G, G to C
RNA polymerase forms phosphodiester bonds between the RNA nucleotides forming a single stranded polynucleotide called messenger RNA (mRNA).
Detail the process of translation (mRNA to polypeptide chain).
Ribosome attaches to a start codon (AUG) and the beginning of the mRNA…
A tRNA with the complementary anticodon (UAC) pairs with the codon on the mRNA through complementary base pairing.
The tRNA is attached to a specific amino acid (Methionine)
Ribosome move over by one codon allowing the next tRNA to bind.
A peptide bond is formed between the two amino acids (peptidyl transferase enzyme / ATP)
Ribosome moves over by one codon and the process continues as the next amino acid is added to the elongating chain.
The process stops when the ribosome meets a STOP codon.
The polypeptide chain starts to fold into its tertiary structure.
