RNA & Protein Synthesis NotesDNA RNA Protein Trait
RNA—Ribonucleic Acid• RNA is a messenger that allows the instruction
of DNA to be delivered to the rest of the cell
• RNA is different than DNA:1.The sugar in RNA is ribose; the sugar in
DNA is deoxyribose
2.RNA is a single strand of nucleotides; DNA is a double strand of nucleotides
3.RNA has Uracil (U) instead of Thymine (T) which is in DNA
4.RNA is found inside and outside of the nucleus; DNA is found only inside the nucleus
• Proteins are composed of amino acids – there are 20 different amino acids
• Different proteins are made by combining these 20 amino acids in different combinations
• Function of proteins:1. Help fight disease
2. Build new body tissue
3. Enzymes used for digestion and other chemical reactions are proteins
(Enzymes speed up the rate of a reaction)
4. Component of all cell membranes
Genes• Genes are the instruction manuals for our
bodies.• They are the directions for building all the
proteins that make our body function.• Genes are made of DNA.
Gene Expression
•Not all genes are active or expressed at the same time. •Why: Because the cell would produce molecules it did NOT need – waste of energy and raw materials
•Gene expression (protein synthesis) is when the product of a gene, or a specific protein is
being produced by a cell.• some genes are – rarely expressed – adrenaline• some genes are – constantly expressed – hair
growth, blood pressure• some genes are expressed sometimes and
turned off others – stress.
Making a Protein—Transcription• First Step: Copying of genetic information from
DNA to RNA called Transcription
Why? DNA has the genetic code for the protein that needs to be made, but proteins are made by the ribosomes—ribosomes are outside the nucleus in the cytoplasm.
DNA is too large to leave the nucleus (double stranded), but RNA can leave the nucleus (single stranded).
• Part of DNA temporarily unzips and is used as a template to assemble complementary nucleotides into messenger RNA (mRNA).
Transcription Animations
• Animated-Steps of Transciption
– http://207.207.4.198/pub/flash/26/transmenu_s.swf
– Transcription Game• http://library.thinkquest.org/20465/g_DNATranscription.ht
m
• More Animated Steps of Transcription
– http://www.wisc-online.com/objects/index_tj.asp?objID=AP1302
Making a Protein—Translation• Second Step: Decoding of mRNA into a protein is
called Translation.• Transfer RNA (tRNA) carries amino acids from
the cytoplasm to the ribosome.
These amino acids come from the food we eat. Proteins we eat are broken down into individual amino acids and then simply rearranged into new proteins according to the needs and directions of our DNA.
• A series of three adjacent bases in an mRNA molecule codes for a specific amino acid—called a codon.
• A triplet of nucleotides in tRNA that is complementary to the codon in mRNA—called an anticodon.
• Each tRNA codes for a different amino acid.
Amino acid
Anticodon
mRNA
tRNA
CAC/CCA/UGG/UGA
___________/___________/___________/____________Histidine1st
Bas
e
2nd Base
3rd Base
Proline Tryptophan Stop
AUG/AAC/GAC/UAA
___________/___________/___________/________Methionine Asparagine Aspartic Acid Stop
Use one of the codon charts on the next page to find the amino acid sequence coded for by the following mRNA strands.
CAC/CCA/UGG/UGA
___________/___________/___________/____________
AUG/AAC/GAC/UAA
___________/___________/___________/____________
Proline Stop Histidine Tryptophan
Methionine Asparagine Aspartic Acid
Stop
Translation Animations
• Animated Steps of Translation– http://207.207.4.198/pub/flash/26/transmenu_s.
swf
• More Animated Steps of Tranlation– http://www.wisc-online.com/objects/index_tj.asp?objID=AP1302
http://www.biostudio.com/demo_freeman_protein_synthesis.htm
http://www.courses.fas.harvard.edu/~biotext/animations/TRANSLATE20b.swf
Movie about translation at bottom of webpage. Click on hyperlink in picture above.
Top Related