1 DNA and RNA Chapter 12
2 12-1: DNA
3 DNA Structure DNA is made up of monomers called nucleotideseach nucleotide is made up of three parts: 1. 5-carbon sugar (deoxyribose) 2. phosphate group 3. nitrogenous base FOUR types of nitrogenous bases adenine (A) & guanine (G) – purines cytosine (C) & thymine (T) – pyrimidines
4 Nitrogenous bases purines (A & G): two ringspyrimidines (C & T): one ring
5 Chargaff’s Rules # of A = # of T # of G = # of C# of purines = # of pyrimidines
6 DNA “double helix” discovered by Watson & Cricktwo strands are wound around each other like a spiral staircase or twisted ladder
7 DNA “double helix” base pairing explains Chargaff’s RulesA always bonds with T (“points”) – double bond C always bonds with G (“curves”) – triple bond
8 So if you have one side of DNA that has these bases,Cytosine (C) Adenine (A) Thymine (T) Guanine (G) --(G) Guanine --(T) Thymine --(A) Adenine --(C) Cytosine These bases will make the other side.
9 DNA Origami
10 Two types of FOLDS
11 Step 1 Cut the white border off the top, bottom, and sides of the template.
12 Step 2 Fold all solid lines going lengthwise down the page into “mountain folds”.
13 Step 3 Fold all dashed lines going lengthwise down the page into “valley folds”.
14 Check Yourself Your paper should look like this:
15 Step 4 Bring the two sides of the model together, similar to an “I” beam.
16 Step 5 Look for the words ‘front’ and ‘back’ at the top of your model. Hold the model with the ‘front’ side facing you.
17 Step 6 Fold the two sides of the DNA model so the ‘front’ side is flat.
18 Step 7 Crease each solid, horizontal line into a mountain fold (away from you).
19 Step 8 Flip the model to the ‘back’ side. Crease each solid diagonal line into a mountain fold (away from you).
20 Check Yourself Your model should look like this.
21 Step 9 Fold ALL of the creases together in the directions of the folds made in steps 7 and 8. Your model will fold up like an accordion. While you are folding, pinch the middle of the model to keep it together to make a cylindrical shape.
22 Step 9
23 Step 10 Release the model. You should be able to see the shape of a double helix.
24 Step 11 Straighten out the sides of the DNA model (the DNA “backbones”) to make them perpendicular to the creases in the middle.
25 You’re DONE!
26 SOL Review A scientists is researching the effect long-term exposure to sunlight has on cell reproduction. Which scenario extends the current understanding of this relationship? A) a culture of liver cells exposed to different pH levels over a 10-day period B) a culture of muscle cells exposed to different nutrients over a 30-day period C) a culture of skin cells exposed to different temperatures over a 50-day period D) a culture of brain cells exposed to different electrical impulses over a 75-day period
27 12-2: Chromosomes and DNA Replication
28 DNA and Chromosomes prokaryotes have a SINGLE, circular chromosome in the cytoplasm containing their DNA
29 DNA and Chromosomes prokaryotes have a SINGLE, circular chromosome in the cytoplasm containing their DNA eukaryotes have MANY chromosomes in the nucleus containing their DNA
30 tightly wound DNA is called chromatidsChromosome Structure DNA is very tightly packed DNA is wound around histones (proteins) to form nucleosomes nucleosomes wind into coils and supercoils to ultimately form chromosomes tightly wound DNA is called chromatids
31 What happens during the S phase of the cell cycle?Flashback! What happens during the S phase of the cell cycle? DNA replicates (copies) itself!
32 DNA Replication
33 DNA Replication C—G G-- --C T-- --A A-- --T G-- --C G-- --Cto make a copy of itself, DNA “unzips” C—G G C T A A T G C G C
34 Notice these strands are the same.DNA Replication new bases come in to make a new complementary strand C—G G--C G --C T--A T--A A--T A--T G--C G--C G--C G--C Notice these strands are the same.
35 Your turn copy and complete the DNA strand C-- G-- T-- A--
36 Does it look like this? C--G G--C T--A A--T
37 “Unzip” and copy it! C—G G-- --C G-- --C T-- --A A-- --T A-- --T
38 Does it look like this? C—G G--C G--C G--C G--C T--A T--A A--T A--T
39 DNA Replication the main enzyme involved in DNA replication is DNA polymerase RESULTS in two identical DNA molecules!
40 SOL Review When designing a scientific investigation, which of the following should be identified first? A) lab equipment needed B) appropriate sample size C) useful analysis software D) a testable hypothesis
41 12-3: RNA and Protein Synthesis
42 RNA vs DNA structure RNA sugar: ribose DNA sugar: deoxyribosesingle-stranded double-stranded uracil (U) base thymine base
43 3 Types of RNA messenger RNA (mRNA) ribosomal RNA (rRNA)RNA is mainly involved in PROTEIN SYNTHESIS messenger RNA (mRNA) ribosomal RNA (rRNA) transfer RNA (tRNA)
44 Protein Synthesis Transcription RNA Editing Translation Overview
45 Transcription DNA is “transcribed” into an mRNA strand with the help of RNA polymerase
46 Transcription how does RNA polymerase “know” where to start and stop making the RNA copy of DNA? the promoter region of the DNA is the start (like the opening song) then the middle part is the coding region, or the gene (like the TV show) the RNA polymerase stops at the termination sequence, the end (like the credits)
47 RNA Editing like a writer’s 1st draftintrons (intervening sequences) are removed exons (expressed sequences) are left to make up the mRNA
48 Translation mRNA “translated” into amino acids (which form proteins!)occurs in the RIBOSOME
49 How does the ribosome “read” the mRNA?using the GENETIC CODE! this “code” only uses 4 letters: A, U, C, G these 4 letters represent 20 different amino acids the code is read 3 letters at a time (in triplicate) – these are called codons example: RNA sequence UCGCACGGU would be read UCG CAC GGU
50 The Genetic Code each codon represents an amino acidthere are 64 codons that code for 20 amino acids 1 start: AUG 3 stops: UAA UAG UGA
51 Translation before translation starts, mRNA is transcribed in the NUCLEUS
52 Translation then, in the cytoplasm, an mRNA molecule attaches to a RIBOSOME translation starts at AUG, and the transfer RNAs come in! (AUG = methionine)
53 Translation it’s a polypeptide “assembly line” of amino acids …
54 Translation … until a stop codon is reached
55 Protein Synthesis
56 SOL Review In 1928 Alexander Fleming observed the mold Penicilium notatum growing in a Petri dish. Also in the dish was the bacteria Staphylococcus aureus. Fleming observed that no bacteria colonies were found growing in the area where the Penicillium notatum was. Which conclusion is BEST defended by Fleming’s discovery? A) P. notatum destroys all colonies of S. aureus B) P. notatum prevents the growth of all bacteria C) P. notatum inhibits the growth of S. aureus D) P. notatum promotes the growth of certain bacteria colonies
57 SOL Review A pesticide manufacturer claims that a new product will decrease the pest population 15% more than the current pesticide for a 10-week period. A population of 50 beetles of the same species is exposed to the new pesticide for a 10-week period. A separate population of the same species of beetle is exposed to the same amount of the current pesticide for a 10-week period. The data collected is sent to an independent research company to verify the results. Which statement BEST explains how an independent research company verifies data to ensure unbiased results. A) The company compares the data given to similar investigations B) The company performs the same investigation and compares results C) The company sends out the data to another researcher to investigate D) The company tests many types of pesticides and draws its own conclusion
58 12-4: Mutations
59 What is a mutation? any change in the DNA sequence two types:1. gene mutations (changes in a single gene) 2. chromosomal mutations (changes in whole chromosomes)
60 Gene Mutations POINT mutations - mutations that affect ONE nucleotide- mainly substituting one nucleotide for another FRAMESHIFT mutations - mutations that affect MULTIPLE nucleotides and shift the “reading frame” - adding/deleting a nucleotide
61 Gene Mutations
62 Gene Mutations
63 Chromosomal Mutations4 types: deletion duplication inversion translocation MUTATIONS
64 Biotechnology Restriction Enzymes – proteins that cut DNA at specific sequences; used for GMOs and DNA fingerprinting; DNA “scissors” Can cut straight across (blunt end) or in a zig zag fashion (sticky end); sticky ends are useful if you want to put the DNA back together
65 Biotechnology Gel Electrophoresis – the process of making a unique DNA “fingerprint” to identify unknown individuals or related individuals Cut DNA into fragments using restriction enzymes Run fragments through a gel using electricity Smaller fragments move further than larger fragments making a banding pattern No two individuals (except identical twins) have the same pattern, but closely related individuals will have similar patterns Used for CSI, paternity testing, and studying evolution
66 Biotechnology Gel Electrophoresis
67 Biotechnology GMOs – “genetically modified organisms”; the process of “cutting” DNA from one species and “pasting” it into another species; also called transgenic organisms or recombinant DNA Cut the desired gene out using restriction enzymes that create sticky ends. Cut the target cell’s DNA with the same restriction enzyme to create a matching sticky end. Use a vector to move the DNA into the target cell Viruses: infect by injecting DNA, so replace viral DNA with target gene to use as a vector. Will work for any cell the virus can infect. Plasmids: circular pieces of DNA that bacteria ONLY will pick up from the environment, place target gene in plasmid to use as a vector Use an enzyme to “seal” the DNA into the new genome
68 Biotechnology GMOs
69 Biotechnology GMO uses –Farmers use GMOs to grow stronger and better crops; GMOs are in just about everything you eat these days Created the industry of “pharming” where we put human genes into bacteria so we can quickly and cheaply produce needed medical hormones such as insulin for diabetics Create “designer” pets and plants, such as trees that glow in the dark to replace street lamps or glow fish to work as night lights Controversial because they are so new; not sure if absolutely safe yet, but only time will tell
70 Biotechnology Cloning – the process of creating an artificial “identical twin” from an existing organism Remove a sample of DNA from the original organism Place the DNA into an emptied egg from the same species Grow the egg in a surrogate mother The baby will be genetically identical to the original
71 Biotechnology Cloning
72 Biotechnology Cloning usesFarmers can clone livestock to create more of the exact same “perfect” specimen Scientists can learn a lot about DNA through cloning or possibly even bring back an extinct species like the Wooly Mammoth to study Doctors can clone single organs, single cells, or even single genes to use as treatments to replace cells that are unhealthy or damaged (instant transplant options or cancer treatments?) Companies can make a lot of money cloning pets