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DNA and RNA Transcription and Translation Comparing Nucleic Acids RNA DNA • Double strand • Thymine • Deoxyribose Sugar • In eukaryotes, inside nucleus • • • • Single strand Uracil Ribose Sugar Can travel in and out of the nucleus through nuclear pores Three types of RNA • mRNA – Messenger RNA – Created based on a gene on DNA • rRNA – Ribosomal RNA – Reads mRNA and assembles materials needed to build proteins • tRNA • Transfer RNA • “Taxi” • Bring materials (amino acids) to the ribosome • What is DNA replication? • When would a cell need to replicate its DNA? When the cell is ready to divide! • could be for growth, or to repair injury Transcription and Translation • What are proteins? – Proteins are a large molecule important to living things – They are made of CHON (carbon, hydrogen, oxygen, nitrogen) – They are built from building blocks called “amino acids” • How does a cell know how to build proteins? – DNA carries all the instructions for a cell • Transcription and Translation What jobs do proteins have? – proteins have many critical roles in living things – Antibodies: fight off foreign particles (like virus/bacteria) – Enzymes: run chemical reactions in cells – Hormones: messenger proteins that travel • Protein Synthesis is a 2-stage process 1. Transcription: make mRNA from DNA gene 2. Translation: read mRNA and build protein Transcription and Translation • How does DNA hold information? – Information is found in the order of nitrgoen bases in DNA (the order of A,C,T, and G’s) • Where is DNA located? – Nucleus of a cell (eukaryotes) • In which organelle do cells build proteins? – Ribosomes Genes • What is a GENE? – A gene is a segment of DNA that gives instructions to build ONE specific protein. – If DNA is a cookbook, each recipe is a gene. – Every cell in your body has the whole cookbook, but only uses some recipes. Genes •Exon: part of DNA sequence expressed •Intron: long noncoding sequences Transcription and Translation Enzymes make an mRNA copy of a portion of DNA • Occurs in the nucleus • Why can mRNA leave the nucleus, but not DNA? Size of the mRNA is small enough to escape the nuclear pores • Where does mRNA go after transcription? Ribosomes! Made of r-RNA! • mRNA is read and the tRNA bring amino acids in order to it build proteins! 1. Helicase enzyme unzips the DNA 2. RNA polymerase reads the selected gene and adds the appropriate RNA nucleotides 3. RNA processing: the introns are cut out 4. The mRNA strand breaks away and DNA rejoins. 5. mRNA can now leave the nucleus and head to the ribosome • There are only ___ nitrogen bases in the “language” of DNA. • There are ___ different amino acids that can be used to build a protein. • How can 4 bases form a code for all 20 amino acids? - By using a codon of three letters for each • Read in groups of three letters: CODON • (DNA gene) AAA GTG GCC ACT • (mRNA) UUU CAC CGG UGA • Read in groups of three: ANTI-CODONS • UUU CAC CGG UGA (mRNA) • AAA GUG GCC ACU (tRNA) • t-RNA is the taxi that brings the amino acids to the Ribosome mRNA: Amino acids UUU CAC CGG UGA PHE HIST ARG stop Ribosome and tRNA • Summarize the steps of Protein Synthesis. • Describe the three types of RNA. • Relate chromosome, gene, sister chromatids and DNA.