Differences between RNA and DNA 1. Sugar in RNA is ribose instead of deoxyribose. 2. RNA is generally single stranded, not double stranded. 3. RNA contains uracil instead of thymine
RNA Is a disposable copy of a segment of DNA FUNCTION: Main function is protein synthesis.
Types of RNA Messenger RNA (mRNA) the RNA molecule that carries the copies of instructions for assembling amino acids. Ribosomal RNA (rRNA) the RNA that combined with many other proteins, make up the ribosomes that assemble proteins Transfer RNA (tRNA) carries amino acids to the ribosomes and matches them to the coded mRNA
What are the 3 differences between DNA and RNA? RNA is a single strand, DNA double RNA has ribose sugar in it, DNA has deoxyribose sugar RNA has the nitrogenous base uracil, DNA has thymine
How is RNA made? By process called transcription. Transcription – process in which segments of DNA serve as templates to produce complementary RNA molecules.
Where transcription occurs In prokaryotes it occurs in the cytoplasm In eukaryotes it occurs in the nucleus.
Transcription 1.The enzyme RNA polymerase attaches to DNA strand 2.RNA polymerase separates the DNA strands 3.RNA polymerase uses one strand to assemble nucleotides into RNA
Where does transcription start? The enzyme RNA polymerase binds to special regions on the DNA called promoters. Promoters – specific base sequences on the DNA that act as signals to show RNA polymerase where to begin transcription
RNA editing Before the RNA can move on to make proteins it must be “edited.” Pieces of the RNA are cut out. The pieces that are cut out are called introns. The pieces remaining in the RNA are called exons.
How is RNA used to make proteins? The nitrogenous bases act as a code for making proteins
Genetic code – The language consisting of 4 letters (A, C, G, and U) that gives the instructions for building amino acids The code is read three “letters” at a time, so each “word” is three bases long
codon – the three letter word that corresponds to a single amino acid
There are 64 different 3 letter combinations of the 4 bases A,T,C and G (so 64 codons) But there are only 20 amino acids. Why aren’t there 64 amino acids? Most amino acids can have more than one codon that codes for them ex. UUA, UUG, CUU, CUC, CUA and CUG all code for the amino acid tryptophan
There are also codons that that code for the beginning and ending of protein synthesis. “start” codons – where the reading of the mRNA begins. (The amino acid methionine is a start codon) “stop” codon- where the reading ends.
*Amino acids bond together to make a polypeptide chain. **Polypeptides- long chains of amino acids joined together.
The amino acids in a polypeptide, and the order in which they are joined, determine the properties of the different proteins.
Translation After transcription the mRNA strand is ready to start the process of protein synthesis. What part of the cell makes proteins? Ribosomes Ribosomes use the sequence of codons in mRNA to assemble amino acids into polypeptide chains.
Translation- The decoding of an mRNA message into a protein (Ribosomes translate the code)
Translation Translation is carried out by ribosomes in the cytoplasm. Step 1: A ribosome attaches to mRNA
Translation Step 2: As each codon passes through ribosome, tRNAs bring the proper amino acid to the ribosome.
tRNA Each tRNA molecule carries just one kind of amino acid. Each tRNA has 3 unpaired bases called an anticodon. Each tRNA anticodon is complementary to one mRNA codon
Translation Step 3: The ribosomes attach the amino acids to the growing chain.
Translation Step 4: The ribosomes helps form a peptide bond between the first and second amino acid.
Translation Step 5: The ribosome then moves to the next codon
Translation Step 6: Polypeptide chain continues to grow until ribosome reaches the stop codon
http://www.stolaf.edu/people/giannini/flashanimat/molgeneti cs/translation.sw f
How are proteins related to traits? Many proteins are enzymes, which catalyze and regulate chemical reactions. Proteins regulate patterns of growth, patterns of development in humans, and they build or operate different components of a living cell.
The Central Dogma Information is transferred from DNA to RNA protein