RNA & Protein Synthesis One gene=one protein
Genetic Code -Universal • All living organisms have the same four nucleotides- A, C, T, & G • Central Dogma: • Information flows from DNA RNA Protein • RNA- Ribonucleic Acid • 1 single chain of nucleotides • RNA nucleotide- 3 parts • Sugar- ribose • Phosphate group • Nitrogen base • Adenine, Guanine, Cytosine, Uracil (instead of thymine) • 3 types of RNA- mRNA; tRNA; rRNA • Base pairing rules: A-U C-G
Triplet Code: • There are 20 amino acids- • 4 nucleotides must combine in groups of three. • 64 codons- (43) • 61 code for amino acids. • 3 are “stop codons” • There is one start codon- AUG- methionine mRNA codon chart
Protein Synthesis- 2 main steps: • 1. Transcription- occurs in nucleus • mRNA( messenger RNA) is made from DNA. • mRNA leaves the nucleus. • DNA stays in the nucleus. • 2. Translation- occurs at the ribosomes • mRNA codons are translated into proteins.
Details, details, details…….. • Transcription- • DNA molecule separates; one chain serves as a template. • Base pair rules apply- A-U; C-G • mRNA (after editing) goes to the ribosomes. • Translation- • mRNA is read by the ribosome. • Translation begins with the start codon- AUG • rRNA(ribosomal RNA) holds the mRNA in the ribosome. • tRNA (transfer RNA) brings the correct amino acid. • tRNA is T shaped: • At one end- anticodon( grouping of 3 RNA nucleotides) that matches up with the mRNA. (base pair rules) • Opposite end -correct amino acid. • Each tRNA is specific for only one amino acid.
Details continued…….. • Amino acids combine to form a protein. • The ribosome reads the mRNA code until a “stop” codon. • Then the ribosome releases the mRNA and the protein is released. • Very fast process- occurs in less than 1 minute. 3 nucleotide terms: DNA= triplet code mRNA= codon tRNA= anticodon Review: mRNA codon chart to determine the amino acids.