tructure of DNA Remember: genes control certain traits, genes are sections of DNA I. tructure of DNA (deoxyribonucleic acid) A. Made of nucleotides 1. nucleotides have 3 main parts a. sugar (deoxyribose) b. phosphate group c. nitrogenous base 2. 4 different nitrogenous bases can be used in a nucleotide a. adenine (A) b. guanine (G) c. cytosine (C) d. thymine (T) B. Watson and Crick 1953 (published) 1. double helix shape (twisted ladder) 2. formed by 2 strands of nucleotides linked together a. sides of the ladder are sugar and phosphate b. rungs of ladder are 2 bases bonded together ***** Adenine always bonds with Thymine! ***** Cytosine always bonds with Guanine!
Adenine = DNA Guanine = Thymine = Cytosine = Four Nitrogenous Bases Nucleotide = sugar, phosphate, base 4 different nucleotides:
Names and Dates: upplement to DNA Notes Watson, Crick and Maurice Wilkins received the Nobel prize in 1962 for their work on DNA structure and how the DNA molecule can function to carry genetic information. February 28, 1953: Crick announces in the English pub The Eagle that he has found the secret of life. Watson and Crick published their work later in 1953. Rosalind Franklin: 1. he worked in the same area of Cambridge University that Watson and Crick did but was in a different college 2. he performed research on the DNA molecule using X-ray crystallography to take pictures; this research was the basis of the double helix shape to DNA that Watson and Crick are so famous for discovering. The idea of a helical shape for DNA was all Rosalind s. Without her work, Watson and Crick would probably have not figured out the DNA molecule before anyone else. 3. he did not like to share her work and her research was stolen by the Watson/Crick/Wilkins lab (they went in and examined everything without her permission), including the famous hoto 51. 4. he was never acknowledged for her contribution to the structure of DNA until Watson described her as a horrible person in his book Double Helix (published 1968). Everyone who was familiar with the DNA story objected and the fact of Rosalind s work being so important was brought to the public s attention.
5. he died at age 37 in 1958, before Watson publishes his book and before the Nobel rize is awarded. he was not mentioned. Maurice Wilkins: Ran the lab that Watson and Crick worked in; oversaw most of their work; received the Nobel rize with Watson and Crick in 1962 Alfred Nobel: Was a major business man in mid to late 1800 s; invented dynamite and made his huge fortune from it; his brother died and a newspaper printed Alfred s obituary by accident and called him the merchant of death (dynamite killed a lot of people in demolition accidents); Alfred hated the thought of his legacy being such a terrible one so when he died he left most of his money for the establishment of the Nobel rizes; it s the highest award a person can receive and covers lots of different categories (literature, physics, medicine, peace...) Chargaff: 1. He studied DNA and analyzed how much thymine, cytosine, adenine and guanine were in each sample. He found that the amounts of thymine and adenine were always equal, and the amounts for cytosine and guanine were always equal. 2. Chargaff figured that adenine and thymine bond together as do cytosine and guanine. The result was Chargaff s Rule: A = T and C = G
I. DNA Replication A. very important that DNA be able to copy itself 1. needed for mitosis and meiosis 2. process of DNA copying itself is called replication B. teps of Replication 1. DNA double helix unzips so that the 2 strands of DNA are separated each separated strand will be a pattern for a new strand of DNA 2. New strands of DNA are formed from single nucleotides in the nucleus called free nucleotides *3. DNA polymerase (an enzyme) matches the bases on the parent strand (the original, unzipped part) one by one with the new bases of free nucleotides 4. trong sugar-phosphate bonds form between nucleotides that are next to one another, creating a new backbone" eventually 2 new double helixes are formed, having 1 parent strand and 1 new strand
I. DNA and RNA A. Both DNA and RNA (ribonucleic acid) are nucleic acids 1. there are structural differences between them DNA Double stranded RNA ingle stranded Base pairs: A T C G Base pairs: C G A U U=uracil; replaces thymine Deoxyribose is the sugar Ribose is the sugar 2. RNA is used for making proteins a. mrna messenger RNA used to send information from DNA to the ribosome b. trna transfer RNA used to match mrna with the right amino acids for making proteins (remember proteins are made of amino acids strung together like the beads of a necklace) II. rotein ynthesis A. protein synthesis is the process by which proteins are made; it has 2 parts: transcription and translation
B. transcription: genetic information from a strand of DNA is copied into a strand of mrna transcribe means to copy teps in Transcription: 1. an enzyme separates (unzips) a section of DNA 2. unattached RNA nucleotides are linked with the matching bases on the DNA strand to form a molecule of mrna 3. after a section of DNA is transcribed, the next section is exposed (unzipped) and the process repeats until DNA signals mrna synthesis to end C. In prokaryotes, mrna goes right to the ribosome for translation to begin In eukaryotes, the mrna is first spliced inside the nucleus. 1. splicing: removing extra parts of mrna that aren t needed After the mrna has been spliced, it leaves the nucleus and travels to the ribosome for translation. D. Translation: process of converting the information in the mrna to a chain of amino acids (protein) 1. in the cytoplasm, one kind of amino acid is attached to each trna; a section of mrna is attached to a ribosome
2. trna s being amino acids to the ribosome, and the amino acids are added one at a time to the growing chain (trna transfers amino acids to the ribosome) Each trna anticodon pairs with a complementary mrna codon, making sure that amino acids are added in the coded sequence 3. codon 3 base section of mrna; most carry a code for a specific amino acid example: UCG codes for tryptophan anticodon sequence of 3 bases found on trna; each trna has only ONE anticodon which complements a specific mrna codon Anticodons and codons fit like plugs into a socket. 4. several codons on mrna have a different purpose they don t code for regular amino acids; instead, they are start and stop codons which signal a ribosome to either start or stop translation. They are located at the beginning and end of an mrna code for a particular protein. 5. Codes for amino acids are universal for all forms of life. They are the same for mice, bacteria, and all other living organisms, even viruses.