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DNA CLIP 1 DNA • located in the nucleus • Function: Carry genetic material • Many People contributed to the discovery of DNA. 2 People Who Discovered DNA • 1928 – Frederick Griffith - DNA = carrier of genetic info • 1944 – Avery – Genes = composed of DNA • 1952 – Hershey and Chase – genetic material = DNA, not protein 3 People Who Discovered DNA • 1952 – Rosalind Franklin – DNA = twisted • 1952 – Edwin Chargraff #A = #T; #C = #G; Chargraff’s Rule • 1953 – Watson and Crick – Discovered structure of DNA we know today 4 5 Shape of DNA 1. Double Helix. -Twisted ladder or spiral staircase 2. Two stranded 3. Held together by hydrogen bonds 4. Made of four Nucleotides 6 Structure of DNA Remember: • DNA is a nucleic acid. • Nucleic acids are made of nucleotides 7 Nucleotides • DNA = long chain of nucleotides • 4 that make up DNA • Have 3 parts: a sugar molecule (deoxyribose), a phosphate group, and a nitrogenous base 8 4 Nitrogenous Bases • • • • 9 Adenine Guanine Cytosine Thymine Sides of the “Ladder” are made up of sugar and phosphate. 10 Adenine always pairs with Thymine Cytosine always pairs with Guanine 11 Would Thymine be able to pair up with Guanine? 12 13 20 14 DNA Replication • Before mitosis, the DNA must be replicated (Copied) exactly. • Each strand can be used to make the other strand. • Many enzymes are involved. 15 Chromosome Structure • DNA is packed very tightly as chromosomes in the nucleus. • Human nucleus has 1 meter of DNA! • Smallest human chromosome has 30 million base pairs. 16 Chromosome Structure • A chromosome has DNA and proteinchromatin. • Tiny sections of DNA are called genes 17 Steps: Semi-conservative replication 1. parent/original strands are unwound with the help of DNA helicases (enzymes). Replication Bubble 18 19 Steps: 2. DNA polymerase attached new nucleotides to the parent strands 20 DNA replication website 21 How a protein is made •Transcription •Translation 22 DNA codes for all of the cell proteins. 23 24 Overview: • DNA is located in the Nucleus • Proteins are made on the ribosomes. • DNA makes a copy (send a message) called “mRNA” 25 Two Steps of Protein Synthesis 1. Transcription 2. Translation 26 Transcription • a copy of the DNA is made…the copy is called messenger RNA or mRNA. • The mRNA takes the code to the ribosome. 27 DNA vs. RNA • Double Stranded • AGTC • Deoxyribose • NEVER! 28 • Single Stranded • AGUC • Ribose • YES! DNA Transcription • During transcription the DNA unzipped and RNA nucleotide are paired up with the DNA bases. • Website 29 30 31 • Once the mRNA copy is made, it can go to the ribosome to be translated. 32 • Remember ….Proteins are made out of amino acids. • There are 20 different amino acids. • 3 bases code for each amino acid = codon. 33 How you figure out which codon is coding for which amino acid… 34 • Once the mRNA gets to the ribosome, the protein can be assembled. • Transfer RNA brings the amino acids to the ribosome. • Website 35 • The three letter code on the mRNA is called a codon. • The three letter code on the tRNA that is matched up with the mRNA is called an anticodon. 36 Review Clip 37 Mutations 38 Mutations • A sudden change in the genetic code is called a mutation. • Most mutations have little or no effect on the organism. • Mutations can be spontaneous or may be caused by environmental factors called mutagens. 39 Mutations in DNA usually occur through one of three processes: 1- DNA damage from environmental agents such as ultraviolet light (sunshine) or nuclear radiation Certain chemicals called mutagens 2- Errors that occur when a cell replicates its DNA in preparation for cell division. 40 Types of Mutations 41 Point mutation -a simple change in a single base of the gene sequence - 3 Types: 1. Point 2. Insertion 3. Deletion 42 Frame-shift Mutations In a frame-shift mutation, one or more bases are deleted or inserted, the equivalent of adding or removing letters in a sentence. Original: THE CAT ATE THE RAT Deletion: THE CAT ATE THE RAT THE CTA TET HER AT Insertion THE CAT ATE THE RAT THE CAT ATT ETH ERA T 43 Chromosomal Mutations • Mutations can occur that involve whole or partial chromosomes – Non-disjunction – homologous chromosomes don’t separate during meiosis – a gamete ends up with an extra chromosome (ex. Down’s syndrome) – Crossing Over – parts of homologous chromosomes are swapped during meiosis 43A Results of DNA Mutations • The results of mutations can be • Helpful – They can result in a helpful trait such as better camoflage CLIP • Neutral – If the mutation does not cause a change in amino acid sequence, or the replaces 1 amino acid with one that is similar, the protein will still function the same. • Harmful – A large change in the amino acid sequence51 can make a protein that does not function at all. 44 53 45 Which of the following is the correct basepairing rule for DNA? A A-U; C-G B A-G; T-C C A-T; G-C D A-C; T-G 46 DNA TECHNOLOGY genetic recombination. 47 DNA Fingerprinting Determining the sequence of bases in DNA for comparisons How they identify criminals and do paternity tests (i.e. “Who is my Baby’s Daddy?”) 48 • • • • • How DNA Fingerprinting works: Scientist cut up DNA into pieces using enzymes Then load the pieces into a gel. Electricity is run through the gel. The pieces of DNA move to the other end of the gel. Smaller pieces move farther. 49 Who doesn’t belong? 50 Recombinant DNA •is a form of artificial DNA where DNA combined that would not normally be combined. •They cut, splice together, and insert the modified DNA molecules from different species into bacteria or another type of cell that rapidly replicates and divides. •The cells copy the foreign DNA right along with their own DNA. •Example: goldfish have genes for fluorescent proteins that have been inserted 51 Genetic Engineering •the manipulation of an organisms genes •applications in medicine and the environment, industry, and agriculture. •Sheep are used in the production of alpha-1 antitrypsin, which is used in the treatment of emphysema. •Goats are also producing the CFTR protein used in the treatment of cystic fibrosis. •Crops are being devised that have natural insect repellants •60 52 Genetic Engineering Example: In the plant world, the buds of cotton plants are vulnerable to worm attacks. The buds of a modified cotton plant resist these worms, resulting in increased cotton production. These gene insertions are ecologically safer than pesticides. They affect only the targeted pest. •53 Clip Scientists today have developed genetically altered bacteria. Among them are strains of bacteria that eat up oil spills manufacture alcohol and other chemicals process minerals. There is concern about possible risks to the environment and the general population as genetically engineered bacteria are introduced. •54 Cloning • Occurs when the DNA from an adult is inserted into the fertilized egg of the organism. • Results in an offspring that is genetically identical to the parent. • The DNA in the egg must be removed before the new DNA is inserted. • Has been used in animals and plants, hopes for the future to allow for the cloning of organs. •55 •55