Presentation on theme: "2.7 DNA Replication, transcription and translation"— Presentation transcript:
1 2.7 DNA Replication, transcription and translation Molecular Biology2.7 DNA Replication, transcription and translation
2 DNA to Protein Synthesis The function of most genes is to specify the sequence of amino acids in a particular polypeptide.Two processes are needed to produce a polypeptide using the base sequence of a gene.TranscriptionTranslation
3 TranscriptionTranscription is the synthesis of mRNA copied from the DNA base sequences by RNA polymerase.The enzyme RNA polymerase binds to a site on the DNA at the start of a geneThe RNA polymerase separates the double strand of DNA and pairs up RNA nucleotides with complementary bases.
4 TranscriptionThe RNA polymerase forms covalent bonds between the nucleotidesTranscription stops at the end of the gene. The completed mRNA is released.
5 TranscriptionThe completed mRNA has a base sequence that is complementary to the template DNA strand.Note: Uracil replaces ThymineComplete the transcription portion of the practice sheet
6 Translation Translation is synthesis of polypeptides on ribosomes Ribosomes are complex structures that consist of a small and large sub-unit with binding sites for each of the molecules used in translation.
7 TranslationThe amino acid sequence of polypeptides is determined by mRNA according to the genetic code
8 TranslationCodons of three bases on mRNA correspond to one amino acid in a polypeptide“Genetic Code” = The translation “dictionary” that enables the cellular machinery to convert the base sequence on mRNA into the amino acid sequence
9 Translation There are 20 amino acids and only 4 nucleotide bases. Living organisms use a triplet code with 3 bases coding for an animo acid.The sequence of 3 bases on the mRNA = CODONExamine the list of codons
10 TranslationThere are 3 “stop” codons that code for the end of translation.Different codons can code for the same amino acid.The code is “degenerate”
11 TranslationTranslation depends on complementary base pairing between codons on mRNA and anticodons on tRNAThe amino acids are carried on tRNAThe tRNA has a 3 base ANTICODON complementary to the mRNA codonComplete the translation portion of the worksheet