RNA Ribonucleic Acid
Question • Use the following diagram to locate the nucleus and ribosomes on the cell.
Key Terms • Ribose: sugar molecule of every RNA nucleotide • Transcription: process by which genetic information is copied from DNA to RNA
The structure of RNA • Like DNA, RNA is a nucleic acid made of repeating nucleotides.
3 Differences Between RNA and DNA • The sugar molecule of RNA nucleotides is ribose. • Uracil usually replaces thymine in RNA. U- replaces T • RNA is single strand
3 Types of RNA • Messenger RNA (mRNA): mRNA carries genetic info. from DNA in the nucleus to the cytosol inside the cell. • Transfer RNA (tRNA): binds to amino acids
3 Types Continued… • Ribosomal RNA (rRNA): most abundant form of RNA, RNA makes up ribosomes where proteins are made.
Transcription • Transcription is the formation of RNA from a DNA template. • The RNA formed may be rRNA, tRNA, or mRNA.
Steps of Transcription • Inside the nucleus, an enzyme, RNA polymerase, binds to bases on the DNA of the gene to be expressed. • This starting sequence is the promotor.
Steps of Transcription • The DNA begins to unwind and the strands begin to separate. • The RNA polymerase begins to move along one strand of the exposed DNA, linking ribonucleotides together in order specified by the sequence of bases on the DNA.
3. Transcription (literally "rewriting") continues until the RNA polymerase reaches a "stop" message on the DNA (a termination signal). 4. The unzipped DNA closes back up and the mRNA is released into the nucleus prior to the next stage in the production of a protein.
Products of Transcription • The RNA formed may be rRNA (ribosomal RNA), tRNA (transfer RNA) or mRNA (messenger RNA).
1. What would the complementary RNA strand be for these DNA sequences? • TACG • ATTAGTC • GATTACA
What would the complementary RNA strand be for these DNA sequences? • TACG • AUGC • ATTAGTC • UAAUCAG • GATTACA • CUAAUGU
Protein Synthesis(translation) • Making proteins • The mRNA now takes the message from DNA to the ribosome to make proteins
What’s the big Deal about proteins???? • Proteins run our show. • Muscles, organs, hair, bone, and skin either contain or are made of proteins. • They are a major component in all of our cells. • Enzymes that run the chemical reactions in our bodies are proteins. • Proteins help us move, send messages (hormones and nerve receptors), fight off disease (antibodies), and transport other molecules and atoms around our bodies.
Proteins • Like DNA and RNA, proteins are polymers. • Proteins are made up of one or more polypeptides, each of which consists of a specific sequence of amino acids. • There are 20 different amino acids • The function of a protein depends how it binds with other molecules in the cell.
Cracking the code The code for proteins is held in the RNA (originally from the DNA) 3 base pairs on mRNA makes up a codon A codon chart is used to tell what 3 base pairs codes for what amino acids.
Translation Translation is the process of reading the mRNA code and using the code to assemble amino acids to make proteins.
Start and Stop Start codons tell translation to begin AUG = start, also codes for the amino acid methionine Stop codons tell translation to stop There are three stop codons These do not code for an amino acid UAA, UAG, UGA
tRNA tRNA contains 3 base pairs that compliment the mRNA codons. The 3 base pairs of tRNA are called anti codons. tRNA links the Amino Acids together with the help of the ribosome to form proteins.
Role of the Ribosome Ribosome are composed of rRNA and proteins. Membrane proteins and proteins to be shipped out of the cell made by ribosome on rough ER.
Ribosome • Ribosome have three binding sites • One for mRNA • Two for holding matching tRNAs • Several ribosome can work on a single mRNA transcript
Completion of a Protein • After the primary structure is complete a protein will fold to form secondary and tertiary structures. • It is at this time you have a completed functional protein.