Molecular Biology and DNA Chapter 10

1. Molecular Biology and DNAChapter 10 • Nucleic acid group • Structure resembles a twisted ladder • Phosphate/Sugar group makes up the rungs of ladder • 4 nitrogen bases make up the steps: A, T, G, C • Structure verified in 1953 by Watson and Crick • Rosalind Franklin credited with helical shape discovery. • Having two sides makes it a “double helix”

2. 4 nitrogen bases pair specifically • Adenine always bonds with Thymine • Cytosine always bonds with Guanine • Remember “At Times, Go Crazy” AT-GC • Each DNA molecule has a specific order of bases…thus each individual has a specific DNA • The way the bases pair up will designate which protein will be formed influencing phenotype of individuals • Thus, you share the same bases as a goldfish or a corn plant, just different amounts of them!

3. When a cell duplicates, where does the extra DNA come from? • Each cell must duplicate DNA exactly • Order of bases must be the same • Replication is semi-conservative…uses part of the original molecule to make new molecule. • Base pairing is important…exact bases must match up to make sure the order is the same • Replication takes place every time mitosis and meiosis takes place

4. Process of making RNA from DNA is called TRANSCRIPTION • ½ of a DNA strand becomes a template, or pattern, for the RNA molecule • Free floating bases in the nucleoplasm will pair up with bases on the DNA creating the RNA molecule, called messenger RNA or mRNA • All T’s will be replaced in the RNA with a U. A, G and C all remain paired the same as in DNA

5. Once in the cytoplasm, TRANSLATION from RNA to protein can begin • mRNA attaches to a ribosome site in the cytoplasm where a rRNA (ribosomal RNA) is located • Free-floating in the cytoplasm are nucleotide bases to pair up on the mRNA. These are called tRNA for transfer RNA. They transfer the bases to the correct site for pairing to make the correct sequence of bases for the protein.

6. Translation results in a chain of amino acids being formed. • Each base group of 3 forms a code for an amino acid. • Different amino acids linked together form a protein. • Since the bases are universal among organisms the code is interchangable. • Proteins will be formed according to the cell that is coding them and the job they need to do • Amino acids come from food you eat and then digest

7. Flow of genetic information in making a protein is important • DNA is in nucleus and cannot leave • Double strand prevents this • Cell must “copy” info on DNA molecule to a single stranded molecule to get the message into the cytoplasm • This is where proteins are made • RNA becomes the copy that carries a DNA code into the cytoplasm • RNA is single stranded and has the base Uracil in place of Thymine

8. Occassionally, a base is out of order and the protein cannot form right. • This creates a mutation • Bases can be added or deleted to create mutations • Added bases bump the chain up one base, deleted bases shift the chain back one base • Enzyme checkers make sure deletions happen very infrequently

9. Viruses…living or non-living? This is a good question!! • Don’t contain any of the 5 properties of living organisms • Do contain genes and have structure • Must insert their own DNA into another cell’s DNA before it can replicate • Then each time a cell replicates by mitosis, it also replicates the virus • In order to eliminate the virus, you must eliminate each cell infected by it • Plants and animals are susceptible to viral infections

10. Occassionally a virus can be used for a good reason. • Viral vectors can be used to carry desirable DNA into cells that lack it. • Example is the DNA for breaking down mucus lacking in people who have Cystic Fibrosis • DNA for human insulin has also been transferred this way to create insulin made in the lab instead of taken from slaughtered cattle and pig pancreases • This helps lessen the chances of allergic reactions to the insulin

11. Recombinant DNA Technology allows us to create unique organisms. • Many products we depend on today are created by mixing DNA from one or more organisms together. • Insulin, vaccine for hepatitis B, human growth hormone, EPO protein to treat anemia • Many “GM” crops are produced this way • Corn, soybeans, alfalfa, wheat, oats, rice with beta-carotene, potatoes with edible vaccine, strawberries with antifreeze

12. FORENSIC SCIENCE AND DNA • DNA fingerprinting common in solving many types of crime cases • Some involve paternity or maternity, others involve murder or kidnapping or burglarly, etc. • Any cells with DNA left by a criminal can have DNA extracted from them for testing • Sometimes use mitochondrial DNA instead of nuclear DNA (chloroplasts contain DNA, too, incase a plant ever becomes a murder!!!) • Order of bases for individuals will be unique • Also used in verifying species claims on food products (caviar from specific fish) • Helps in identification of fossils, bones and pieces of organisms