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“Building Blocks of Life” DNA—a chemical that contains information that an organism needs to grow and function Mid-1800’s: Scientist know nuclei of cells contain large molecules By 1950: Chemists identify what DNA was made of 1952: DNA is discovered to exist in a spiral form 1953: Watson and Crick make a model of the DNA molecule Picture a twisted ladder › Sides of ladder: Deoxyribose and phosphate › Rungs of ladder: nitrogen base pairs A = Adenine G = Guanine C = Cytosine T = Thymine Bases always come in pairs Adenine always Guanine always matches Thymine matches Cytosine Before mitosis or meiosis, DNA gets copied. How does this happen? 1. The bonds between the nitrogen bases are broken by an enzyme 2. The two sides of the DNA unwind and separate 3. New bases pair with bases on original DNA All of your characteristics are determined by your DNA Gene – sections of DNA on a chromosome › Genes contain instructions for making specific proteins › But… genes are on chromosomes, which are in the nucleus… proteins are made on the ribosomes in the cytoplasm… › How do the protein codes get to the ribosomes? Ribonucleic Acid! RNA carries the codes for making proteins from the nucleus to the ribosomes in the cytoplasm RNA is similar to DNA except: 1. has one strand instead of two strands. 2. has uracil instead of thymine 3. has ribose instead of deoxyribose (sides of ladder on DNA) Protein production begins when messenger RNA (mRNA) moves into the cytoplasm mRNA carries the code for making proteins Ribosomal RNA (rRNA): makes up ribosomes, where proteins are built. Transfer RNA (tRNA) brings amino acids to the ribosomes to build the protein. All of your cells have the same DNA Cells use the genes they need to do their job and ignore the other genes Example: Cells in your stomach produce the proteins needed to digest your food while muscle cells produce proteins to make your muscles move. Sometimes mistakes happen when DNA is being copied. Mutations—any permanent change in the DNA sequence of a cell’s gene or chromosome Can be caused by outside factors like X rays, sunlight, and some chemicals A change in a gene or chromosome can change the traits of an organism. Can sometimes be fatal. What are the nitrogen base pairs in a DNA molecule? A strand of DNA has the bases AGTAAC. Use letters to show what the matching strand would be Adenine, Guanine, Cytosine, Thymine TCATTG What are the nitrogen base pairs in an RNA molecule? A strand of DNA has the following order of bases: CGTATCGA. The corresponding order of bases in the matching RNA will be? Guanine, Cytosine, Adenine, Uracil GCAUAGCU You begin as one cell. Compare the DNA in your brain cells to the DNA in your heart cells. Describe how DNA makes a copy of itself DNA in all types of cells is identical Two sides unwind and are separated by an enzyme; a complementary strand is formed for each; the resulting double stranded DNA has one original strand and one new strand What are the 3 types of RNA? What do they do? mRNA – carries code from nucleus to ribosomes rRNA – makes up the ribosomes tRNA – brings amino acids to ribosome to build the proteins