From Genes to Proteins

DNA and RNA differ in 3 ways Single-stranded Ribose (sugar) Uracil (base)  bonds to Adenine DNA Double-stranded Deoxiribose (sugar) Thymine (base)  bonds to Adenine

The Flow of Information

The Flow of Information

Transcription This is the first step in Protein Synthesis: 1. The instructions are transferred (“transcribed”) to an RNA molecule.

To sum up Transcription… What is the Enzyme involved in Transcription? Info transferred from DNA to RNA What is the Enzyme involved in Transcription? Answer  RNA Polymerase

Transcription has 3 steps… 1 – RNA Polymerase binds to the gene’s promoter (DNA)  (like a starting line in a race).

2 – RNA Polymerase UNWINDS the DNA molecule 2 – RNA Polymerase UNWINDS the DNA molecule. The DNA nucleotides are exposed.

3 – RNA Polymerase (yeah, that same enzyme again…) adds complimentary nucleotides to separated DNA strand. ** Remember  RNA has Uracil instead of Thymine for a base.

The RNA Polymerase will continue transcription until it reaches the “stop signal” on the DNA molecule (like a finish line). Then the RNA strand is released and goes on to the next step…Translation

Transcription

Transcription

3 types of RNA mRNA (messenger RNA) rRNA (ribosomal RNA) tRNA (transfer RNA)

Messenger RNA Delivers information to the site of Translation.

mRNA instructions are written in “3-nucleotide” sequences. These sequences are called codons. Ex. See pg. 209 UUU, CUG, ACU, etc. There are 64 possible codons.

Translation Remember what happens in Transcription? DNA to RNA In Translation…RNA is coded for Amino Acids.

Translation takes place in the Cytoplasm. tRNA (Transfer RNA) molecules carry single amino acids. They also have an OPPOSITE “3-nucleotide” sequence called anticodons.

rRNA (Ribosomal RNA) molecules are like assembly lines  they carry: 1 mRNA 2 tRNA

7 Steps in Translation 1 – mRNA start codon starts the process at the P site. 2 – the next tRNA bonds to the next codon at the A site. 3 – A & P are holding 2 tRNA’s…a peptide bond is formed between 2 amino acids.

4 – tRNA detaches from P-site, leaves behind amino acid, leaves Ribosome. 5 – tRNA at A-site moves to the P-site. Now a new codon is ready at the A-site for another tRNA.

6 – tRNA detaches from P-site, leaves behind amino acid, leaves ribosome. 7 – (Steps 2 – 6 repeat until a stop codon is reached). Ex. UAG, UAA, UGA. A new protein is then released into the cell.

Translation

Translation