DNA, Cell Cycles and Genetics! Mrs. Stahl Biology
Let s Think!!!! What does DNA stand for? Where is DNA located in the cell? What is DNA to you? Where do we find DNA?
1928- Fredrick Griffith s Experiment Looked into the bacterium that causes pneumonia. One form is coated by carbohydrates and is called the smooth (S form), while the other form is rough. S type killed the mice. S type that was heated before injection= mouse lived. Combo- R and heat treated S= mice died. Found S bacteria in the blood. Some of the S bacteria must have transferred into the R. The R became harmful. Conclusion: Transforming Principle
Why did this happen? Heating bacteria to 60 C (140 F) can kill the bacteria without denaturing (falling apart) their DNA. DNA can remain unchanged up to 90 C (194 F). Therefore, the S bacteria in Griffith s experiment died, but their DNA remained intact.
Oswald Avery- 1944 Figured out what the transforming principle was by observing it in a petri dish. Conducted three tests: 1. Qualitative- chemical tests showed that there weren t any proteins, but DNA was present. 2. Chemical Analysis- Elements in the extract (sample) closely matched those found in DNA. 3. Enzyme Tests- tested the reaction to certain enzymes. Added to the extract enzymes that breakdown proteins, the extract still transformed the R bacteria to the S form. Transformation did not occur when they added an enzyme to destroy the DNA. Conclusion- DNA is the transforming principle.
Hershey and Chase 1952 Studied bacteriophages-> a type of virus that takes over a bacterium s genetic machinery, and directs it to make more viruses. They are the ones responsible for confirming that DNA is the genetic material. They used radioactive sulfur (found in proteins ) and radioactive phosphorus (found in DNA)
Hershey / Chase Experiment Experiment 1: Infected bacteria with bacteriophages grown in radioactive sulfur; separated bacteria from the phages, found no activity in the bacteria. Experiment 2: Infected bacteria with bacteriophage grown in radioactive phosphorus; separated bacteria from bacteriophages; found significant radioactivity inside the bacteria, which showed that DNA from the bacteriophage had entered the bacteria.
Final Result DNA is the genetic material.
Chargaff- 1950 Analyzed the DNA of many different organisms. Found that the same four base pairs are found in the DNA of all living organisms. Amount of adenine = thymine Amount of cytosine= guanine
Rosalind Franklin & Wilkins Pioneer- woman She used x-rays to study DNA s crystalline structure. When the x-ray hits the DNA, the atoms in the DNA bend the x-rays in a pattern. Franklin s x-rays were shaped like an X surrounded by a circle. Her data suggested that the pattern and angle of X showed that DNA is made up of two strands that look like a helix, and are constant in width.
More on Rosalind Franklin https://www.youtube.com/watch?v=bip0lyr diri
Watson and Crick determined the threedimensional structure of DNA by building They realized that DNA is a double helix that is made up of a sugarphosphate backbone on the outside with bases on the inside. models.
Introduction to DNA https://www.pinterest.com/pin/3208821607 6576033/
The Structure of DNA Deoxyribonucleic acid Very long polymer or chain of repeating units Monomers are called nucleotides Each nucleotide is made up of a sugar (deoxyribose), phosphate (one phosphorus with four oxygen), and nitrogenous base (ATGC) A= Adenine T= Thymine C= Cytosine G= Guanine
Structure Continues Double helix / twisted ladder Backbone= sugars and phosphates Strands are complementary - they fit together and are opposite each other. Base pairs are held together by hydrogen bonds. Sugars and phosphates are held together by covalent bonds. http://www.youtube.com/watc h?v=p835l4hwh68
Why would the middle / nitrogenous bases be held together by hydrogen bonds and the backbone or sides be made up of covalent bonds?
Answer Base pairs are held together by weak, hydrogen bonds because the strands need to be able to break apart so that they can replicate. The sides of the latter need to be strong to keep the strands in tact when it splits to replicate.
Label the DNA Molecule
Hydrogen Bonds Phosphates T A C Sugars G A C T G Covalent Bonds
Chargaff s Rule Base pairs match up A always binds with T (held together by 2 hydrogen bonds) C always binds with G (held together by 3 hydrogen bonds) The bonds that hold them together are hydrogen bonds Example- ACACAC, what is the complementary strand? G A C T
Phosphates Sugars hydrogen bond covalent bond
1. TGCATTGC 2. ATATAGCTAG 3. ATA 4. CAT 5. TATGC Let s Practice- Find the Complementary Strand
Review Questions 1. Write out the full name for DNA. 2. What is a gene? 3. Where in the cell are chromosomes located? 4. DNA can be found in what two organelles? 5. What two scientists established the structure of DNA? 6. What is the shape of DNA? 7. What are the sides of the DNA ladder made of? 8. What are the "rungs" (steps) of the DNA ladder made of? 9. What sugar is found in DNA? 10. How do the bases bond together? A bonds with G bonds with 11. DNA is made of repeating units called.. 12. Why is DNA called the "Blueprint of Life? 13. What holds the sides of the DNA ladder together?
DNA is constantly being replicated or copied. Old cells die and new cells are created! Let s see how this is done!
DNA Replication The process by which DNA is copied during the cell cycle and occurs in the nucleus. A single DNA strand can serve as a template or pattern for a new strand. Assures that every cell has a complete set of identical genetic information. Your DNA is divided into 46 chromosomes that are replicated during the S phase of the cell cycle (interphase). Your DNA is copied once in each round of the cell cycle = complete set of DNA for each cell.
The Importance of Proteins in the Process DNA just stores information. Enzymes and proteins really do all the work. Some enzymes will unzip the DNA, while others piece it back together. Nucleotides- free floating in the nucleus and have the ability to pair up with other free floating nucleotides of the existing nucleotides.
What is a nucleotide made up of?
Answer Sugar, phosphate, and a nitrogenous base.
Enzymes of Importance DNA polymerase- bonds the new nucleotides together (DNA polymer- tells us what the enzyme does= makes DNA polymers, ase= enzyme). Polymerase I- Acts on the lagging strand to remove primers and replace them with DNA. Polymerase II- No role in replication, but is involved in DNA repair processes. Polymerase III- Main replication enzyme. Responsible for the bulk of DNA synthesis.
DNA helicase- The enzyme unzips the double helix in both directions to separate the strands of DNA. Breaking the hydrogen bonds holding them together. DNA ligase- Enzyme that seals repairs in the DNA, joins the Okazaki fragments together to make one strand, and it seals recombination fragments. RNA primase- Enzyme that goes over a single DNA strand and creates RNA sequences called primers; which transcribe DNA into RNA. Primers: Short strand of RNA or DNA that serves as a starting point to make more (synthesis) Think of it like cover-up- you prime your face before you put makeup on. Topoisomerase- Enzyme that prevents the DNA from getting tangled up. https://www.youtube.com/watch?v=eygrelvyhnu
Exonucleases- Enzymes that chew away at the end of DNA. Proofreading function; allows the enzyme to remove a mispaired base.
The Replication Process- Step 1 1- DNA helicase unzips the double helix. It breaks the hydrogen bonds connecting the base pairs; separation of strands occurs and the bases from each side are exposed (think of it like unzipping your jacket- both sides of your jacket are exposed). This area or junction is called the replication fork. Important to remember: the DNA molecule unzips in both directions.
Step 2 2. The existing strand is a template for the new strand. Free floating nucleotides pair up with the bases from the template strand. DNA polymerase bonds them back together to form new strands.
Step 2 Continues: Leading and Lagging Strands One side is the leading strand - it follows the helicase as it unwinds in the 3 to 5 direction, DNA replication occurs in a smooth, continuous one way direction. The other side is the lagging strand - moving away from the helicase (in the 5' to 3' direction), DNA replication occurs in a discontinuous, short section in the opposite direction (Okazaki fragments). DNA ligase joins the Okazaki fragments together.
Step 3 Two identical molecules of DNA is the end result. One strand is the original, while the other is the new strand. Semi-conservative: one old strand is conserved (saved) and one new strand is made.
Remember HOW the Carbons Are Numbered! Phosphate Group O O=P-O O Sugar (deoxyribose) 5 CH2 C 4 O C 3 C 2 Each carbon is numbered 1-5. Draw this into your notes. This is important because DNA polymerase only adds nucleotides to the 3 end, so the new DNA can elongate only in the 5 to 3 direction. C 1 Slide taken from cmassengale N Nitrogenous base (A, G, C, or T)
The DNA molecule unzips in both directions. Step 1 Step 2 new strand nucleotide DNA polymerase
original strand new strand Two molecules of DNA Stage 3
Replication is fast and accurate. DNA replication starts at many points in eukaryotic chromosomes. There are many origins of replication in eukaryotic chromosomes. DNA polymerases can find and correct errors.
Replication Practice See handouts and Amoeba sisters video notes. https://www.youtube.com/watch?v=5qsrme iwsuc
Foldable Color the foldable accordingly. DNA template strands= blue DNA helicase= orange Topoisomerase= brown Nucleoside triphosphates= light little T s are red, the dark little T s are black. DNA polymerase III= green RNA primase= purple DNA ligase= pink DNA polymerase I- yellow Single stranded binding proteins= red
Cell Cycle
Why do you always have to cut your hair, fingernails, and the lawn? Growth, caused by new cells being made. Let s see how that happens!
The Cell Cycle is a regular pattern of growth, DNA duplication, and cell division that occurs in eukaryotic cells. During the Cell Cycle a cell grows, prepares for division, an divides to form two daughter cells, each of which begins the cycle again. Interphase is the period of growth that occurs between cell divisions. Prepares the cell to divide. Interphase is divided into three phases: G1, S, and G2
G1 or Gap 1 S phase Synthesis G2 or Gap 2 The G1 phase is a period of activity in which cells do most of their growing. Cells will increase in size and synthesize new proteins and organelles. Critical checkpoint to make sure that there are no imperfections. The S phase replicates chromosomes and synthesizes DNA molecules. When DNA replication is completed, the cell enters the G2 phase. By the end the cells nucleus contains two complete sets of DNA. During the G2 phase, many of the organelles and molecules required for cell division are produced. When G2 is completed, the cell is ready to enter the M phase (mitosis). Critical checkpoint to make sure that the DNA is not damaged and that the cell is adequate size.
Spindle Fiber
Mitosis We will come back to this in just a few slides
Cells divide at different rates. The rate of cell division varies with the need for those types of cells. Some cells are unlikely to divide (G 0 ). Why?- If they are not needed right away, they won t replicate or need to replicate.
Cells divide at different rates- cont. G o = cells that rarely divide but still function Ex- neurons and muscle cells Ex- lymphocytes= part of your immune system -> B cells and T cells. They don t divide until they recognize an invader and then they rapidly divide to fight that antigen.
Cell Size Cells are limited in size by their surface area to volume ratio. Cells can get so large that they will not be able to obtain enough oxygen and nutrients, at that point they will divide or die.
Surface area must allow for adequate exchange of materials. Cell growth is coordinated with division. Cells that must be large have unique shapes.
Mitosis Mitosis is defined as the division of the nucleus and its contents. Cytokinesis is the division of the cytoplasm Results in 2 identical daughter cells. In this process the nuclear membrane dissolves, and the duplicated DNA condenses around proteins and separates; resulting in two nuclei formed.
Terminology First Chromosomes- long continuous strands of DNA. Histones- A group of proteins that your chromosomes are associated with. Chromatin- loose combination of DNA and proteins; looks like spaghetti. Chromatid- one half of the duplicated chromosome. Centromere- the center where sister chromatids are held together. Telomere- the ends of the chromosomes, and they prevent the chromosomes from accidently attaching to one another, as well as prevent gene loss.
Chromosomes Long continuous thread of DNA with lots of genes that regulate your entire body. Body= 46 chromosomes / 23 pair In just one cell it is about 3ft long DNA wraps around proteins called histones. DNA and histones form chromatin (looks like spaghetti- interphase) Chromosomes condense tightly for mitosis-> duplicated; looking like an X.
DNA wraps around proteins (histones) that condense it. DNA double helix DNA and histones Chromatin Supercoiled DNA
DNA plus proteins is called chromatin. One half of a duplicated chromosome is a chromatid. Sister chromatids are held together at the centromere. Telomeres protect DNA and do not include genes.
Mitosis- See Foldable You will need the following colors: Centrioles & Spindle Fibers= orange Yellow, red, green, and blue = DNA Nucleolus- pink
Interphase- Before S Phase DNA is long, thin, thread-like chromatin. One pair of centrioles / centrosomes
Interphase After S phase DNA has duplicated forming sister chromatids joined at the centromere. Centriole pair / centrosome has duplicated.
MITOSIS- Prophase DNA begins to thicken and condense. Centrioles pair / centrosome begin to migrate to opposite poles with spindle fibers forming between them. Nuclear membrane & nucleolus start to dissolve.
Mitosis- Prometaphase Centrioles move further away. Nuclear membrane further dissolved and nucleolus is gone. Kinetochore spindle fibers capture kinetochores (complex of proteins) of chromosomes and begin to move toward the equatorial plate (middle).
Mitosis- Metaphase Middle Chromosomes align along the equatorial plate. Spindle apparatus / mitotic spindle fully formed.
Mitosis - Anaphase Apart Kinetochore microtubules shorten and pull apart sister chromatids at the centromere an drag the chromatids to opposite poles. Separated sister chromatids are now considered chromosomes.
Two Nuclear membrane & nucleoli begin to reform. Spindle apparatus disassembles. Cleavage furrow in animal cells (cell plate in plant cells) form to separate the cytoplasm to create two identical daughter cells. Mitosis - Telophase
Below Telophase on Foldable Cytokinesis: division of the cytoplasm. Results in two identical daughter cells.
Videos https://www.youtube.com/watch?v=f-ldpgefahi
Fill it out!
Videos http://www.youtube.com/watch?v=vln7k1-9qb0 http://www.pinterest.com/pin/320882160698 18262/
Regulation of the Cell Cycle External Outside the cell 1. Cell to cell contact. When one cell touches another, it stops growingunknown. 2. Some cells send chemical messages telling others to grow. Cancer cells Hemophilia Growth hormones Internal Inside the cell A lot of times they are triggered by external factors Kinase and cyclin Kinase is an enzyme that transfers phosphates all over your body, but the ones that trigger the cell cycle are called cyclinsproteins involved in the cell cycle.
Apoptosis is programmed cell death A normal feature of healthy organisms Caused by a cells production of self-destructive enzymes Occurs in development of infants webbed fingers
Cell division is uncontrolled in cancer Cancer cells form disorganized clumps called tumors. Benign tumors remain clustered and can be removed. Malignant tumors metastasize, or break away, and can form more tumors. normal cell cancer cell bloodstream
Carcinogens are substances known to promote cancer. Standard cancer treatments typically kill both cancerous and healthy cells. http://www.pinterest.com/pin/320882160696 39864/
Reproduction
Sexual Reproduction Sexual reproduction- the joining of two specialized cells called gametes. Gametes= sperm and eggs
Asexual Reproduction Creation of offspring from one parent. No gamete exchange! Offspring are genetically identical to parent. Examples include Amoebas Hydras Fungi Bacteria Archaea Protists Sea anemones Coral Sea Stars Some non-flowering plants Strawberry Onion Potato
Example 1- Mushrooms (FUNGI)
Hydras http://www.youtube.com/watch?v=a5ohmjgq jyo&feature=related
Amoeba
Bacteria http://www.youtube.com/watch?v=dy9dnwc qxi4
Sea Anemones http://www.youtube.com/watch?v=spwi2qclk ao
Sea Star
Binary fission Most prokaryotes Results in 2 identical daughter cells, just like mitosis. parent cell DNA duplicates cell begins to divide daughter cells
Budding- eukaryotes through mitosis Examples A new plant growing from cutting the stem. Hydra Defined as: Small projection that grows on the surface of the parent organism, forming a new organism. Hydra bud Yeast
Fragmentation Examples Sea Star- parent splits into pieces. Flatworms Defined As: The splitting of the parent into pieces that each grow into a new organism.
Vegetative Reproduction Examples Strawberries Potatoes Defined as: Forms a new plant from the modification of a stem or underground structure on the parent plant.
Advantages of Asexual Reproduction 1. They all can reproduce a lot and quickly. 2. More efficient in favorable environments 3. They don t have to worry about attracting a mate.
Disadvantage of Asexual Reproduction 1. Mutation in a population could cause the entire population to die. 2. So many at one time can cause competition with food and space. 3. Extreme temperatures can wipe out entire colonies, leading to extinction.
MEIOSIS
Your body has two types of cells. Somatic Cells / Body Cells Makes up most of your body and tissues. Ex- heart, kidneys, eyeballs, etc. DNA in your body cell is not passed on to your children. Sex Cells / Germ Cells Cells in your reproductive organs. Ovaries and testes that develop into sperm and eggs= your gametes. DNA is spread to your child.
Your Cells have Autosomes and Sex Chromosomes. 23 pairs of chromosomes = 46 total in humans Get 23 from mom and 23 from dad Each pair = homologous chromosome = means having the same structure. Homologous Chromosomes- two chromosomes, one from mom and one from dad, that have the same length and general appearance. The chromosomes have copies of the same genes, but they may differ.
Autosomes Chromosome pairs 1-22 Not related to the sex of the organism.
Sex Chromosomes Pair number 23 In humans- XY= male, and XX= female They are not homologous X chromosome is larger and carries more genes than the Y, which is smaller and carries fewer genes.
Karyotype a picture of your chromosomes. Homologous Chromosomes Autosomes Sex Chromosomes
Questions???????????? What is pair 23 called? Is it a male or female? How many total chromosomes are there? Which sex chromosome is always larger?
Find the Homolog
Answers!!!! Chromosome #5 Chromosome # 12
Sexual Reproduction The fusion of two gametes; resulting in the genetic mixture of both parents!
Fertilization The actual fusion of the sperm and the egg. When it occurs, the nucleus of the egg and the sperm become one.
Diploid and Haploid Cells Cells have two copies of each chromosome. One from mom and one from dad. Body cells 2n Diploid Diploid number in humans = 46 because 2 X 23 = 46 Each human egg or sperm has 22 autosomes and only 1 sex chromosome. Haploid Cells have only one copy of each chromosome. Gametes / germ cells N Haploid number in humans = 23
Process of Meiosis Results in 4 genetically different haploid cells Two rounds: Meiosis 1 and Meiosis 2 Meiosis 1- divides the homologous chromosomes Meiosis 2- divides the sister chromatids Reduces chromosome number and increases genetic diversity Sex Cells or gametes that are dividing.
Homologous Chromosomes and Sister Chromatids- How do I tell them apart? Homologous Chromosomes- Two separate chromosomes, one from your mom and one from your dad. They are the same length and carry the same genes, but they are not copies of each other. Sister chromatid: Each half of a duplicated chromosome is called a chromatid, and together they are called sister chromatids, and are held together at the centromere.
Homologous chromosomes Sister chromatids Sister chromatids
Refer to the Meiosis Foldable
Meiosis I occurs after DNA has been replicated. Meiosis I divides homologous chromosomes in four phases.
Meiosis II divides sister chromatids in four phases. DNA is not replicated between meiosis I and meiosis II.
Prophase 1 of Meiosis -Homologous pairs form -Line up closely next to each other= tetrad. - When tetrad forms the homologues exchange DNA at various loci called chiasmata= recombinant DNA= CROSSING OVER = random genetic variation! -Nuclear membrane breaks down, nucleolus dissolves, and centrioles migrate.
Why is crossing over important? Gives rise to genetic recombination. Genetic material between mom and dad is being exchanged.
Metaphase 1 Homologous chromosomes are aligned in the middle by spindle fibers. Each side of the equator has chromosomes from both parents. Random genetic variation occurs again. Random sorting = Independent Assortment Results in 8,388,608 possible chromosome combinations.
Anaphase 1 Spindle fibers attach to homologous chromosomes and pull them to opposite poles. Cell enlarges and elongates.
Telophase 1 - Two distinct cells begin to form that are NOT IDENTICAL. One set of DNA on each side. Haploid # on each side. - Cleavage furrow forms / cytokinesis begins
Between Meiosis I and II DNA is not replicated again between I and II.
Prophase II Nuclear membrane begins to dissolve. Chromosomes condense and thicken Nucleolus begins to disappear Centrioles migrate Spindle fibers form
Metaphase II Spindle fibers align chromosomes along the cells equator. Random genetic variation occurs again Centrioles migrate to opposite poles
Anaphase II Spindle fibers attach to sister chromatids and pull, which separates them at their centromeres. Cell elongates.
Cells separate DNA decondenses back into stringy chromatin Nuclear envelope reforms Nucleolus reappears Spindle fibers dissolve Telophase II
END RESULT 4 genetically different haploid cells!!! The 4 cells in the foldable are a result of spermatogenesis= 4 sperm are created. Oogenesis- the process of producing female gametes= 1 egg and 3 polar bodies (don t take part in reproduction).
Review.. Mitosis Produces 2 genetically identical diploid daughter cells Takes place throughout an organisms lifetime Involved in asexual reproduction. Occurs only in body cells. Responsible for the growth, repair, and development in all types of organisms. Meiosis Produces 4 genetically different haploid cells Takes place only at certain times in an organisms life cycle. Involved in sexual reproduction- DNA is copied once but divided 2X s. Occurs only in sex cells / germ cells to produce gametes. Sometimes called reduction division because it divides the cells chromosomes by half.
BELLWORK What type of cell division occurs in prokaryotic cells like bacteria? Which type produces normal body cells with the same chromosome number as the parent cell? Which type produces gametes (sex cells) and reduces the chromosome number by half? When do chromosomes first become visible? When are chromosomes not visible? When do the chromosomes line up at the cell's center? When do chromosomes move toward opposite poles? When does the nuclear membrane break down? When does the nuclear membrane reform around each daughter nucleus? When does the cytokinesis start? When do we find the G1, S, and G2 phases? What are three reasons that cells divide periodically?
What are two ways that sperm cells differ from egg cells in their production and appearance? In eukaryote cells, which type of cell division produces two cells? In eukaryote cells, which type of cell division produces four cells? What is one advantage of asexual reproduction over sexual reproduction? What is one advantage of sexual reproduction over asexual reproduction? Region of a chromosome where two sister chromatids are held together by Rod - shaped, coiled combination of DNA and protein that occurs during cell division is called a One of the two identical parts of a chromosome is known as Referring to a cell having the normal(2n) number of chromosomes is called the Referring to a cell having half (n) the normal number of chromosomes is called the Reproduction in which one parent is involved is called Reproduction involving two parents and the union of an egg and a sperm is called