LG 4 DNA and Protein Synthesis

Ribonucleic AcidRNA –Steps in Protein SynthesisTranscription –Translation –Functions of ProteinsStructural –Signals –Enzymes –Carriers –

Unit IV - GeneticsLearning Goal 4

Describe how DNA is used by cells to produce proteins.

RNA

• RNA (ribonucleic acid) is another type of nucleic acid that plays a role in decoding DNA.

• RNA is different from DNA in the following ways:

• It contains uracil instead of thymine

• It contains ribose instead of deoxyribose

• It is single stranded instead of double stranded

Steps in Protein Synthesis

• Transcription• A section of DNA

called a gene contains the code for a certain protein.

• When the protein is needed by the cell, this section unwinds.

• RNA nucleotides line up and bond with their complimentary nitrogen bases on the appropriate side of the exposed DNA

• G-C, C-G, U-A, A-T• When transcription is

complete, messenger RNA (mRNA) separates from the DNA and moves out of the nucleus into the cytoplasm where it hooks up with ribosomes.

Translation• Transfer RNA (tRNA)

brings amino acids to complimentary regions on the mRNA.

• These regions are called codons and are 3-letter segments

• The 3-letter tRNA segments are called anti codons

• Amino acids are positioned side by side and bond together to form polypeptides, which then become part of protein molecules.

Functions of Proteins

• Structural (muscles, connective tissue)• Example: collagen

• Signals (hormones, neurotransmitters)• Example: insulin that signals cells to take in

glucose

• Enzymes that speed up chemical reactions in cells

• Example: lipase for fat digestion

• Carriers that move substances around in the body.

• Example: hemoglobin that carries oxygen to cells.

• http://www.youtube.com/watch?v=h3b9ArupXZg&feature=player_detailpage

• http://www.youtube.com/watch?v=gqvYOr78THo&list=RD02iSt7oh9E1Dg&feature=player_detailpage