Cell Cycle, Dna, And Protein Synthesis Notes New


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Cell Cycle, Dna, And Protein Synthesis Notes New

  1. 1. Cell Cycle, DNA, and Protein Synthesis
  2. 2. The Cell Cycle <ul><li>We have learned that the basic unit of life is the cell . </li></ul><ul><li>Like all living things, the cell goes through a cycle of growth and reproduction . </li></ul><ul><li>The sequence of growth and division of a cell is called the Cell Cycle . </li></ul><ul><li>Most of the cell’s life is spent in the growth phase known as interphase </li></ul><ul><ul><li>made up of three phases: G1, S, and G2 </li></ul></ul><ul><li>The shortest phase in the cycle is the cell division phase known as mitosis and cytokinesis . </li></ul>
  3. 3. The Cell Cycle (see diagram on page 228) G1 – GAP 1 – Chromosomes are not visible (chromatin) Cell is rapidly growing and synthesizing proteins for daily functions S Stage - Synthesis Chromosomes are replicated to form a pair of sister chromatids connected by a centromere G2 – Gap 2 - Cell is growing and producing proteins needed for mitosis Mitosis - Cell divides the nucleus followed by cytoplasm division (cytokinesis) resulting in two identical daughter cells
  4. 4. Mitosis <ul><li>During mitosis, one parent cell divides into two identical daughter cells. </li></ul><ul><li>All somatic cells (cells other than the sex cells that make eggs and sperm) undergo mitosis . </li></ul><ul><li>There are four phases of mitosis: </li></ul><ul><ul><li>Prophase </li></ul></ul><ul><ul><li>Metaphase </li></ul></ul><ul><ul><li>Anaphase </li></ul></ul><ul><ul><li>Telophase </li></ul></ul>
  5. 5. Prophase <ul><li>This is the first and longest phase in mitosis. </li></ul><ul><li>The nuclear envelope disappears </li></ul><ul><li>Chromatin coils to become visible chromosomes </li></ul><ul><li>The two halves of the doubled structure are called sister chromatids . </li></ul><ul><li>Sister chromatids are exact copies of each other and are held together by a centromere . </li></ul><ul><li>In animal cells, the centrioles move to opposite ends of the cell and start to form spindle fibers </li></ul>
  6. 6. Metaphase <ul><li>The second and shortest phase in mitosis </li></ul><ul><li>The spindle fibers attach to the centromere </li></ul><ul><li>The sister chromatids are then pulled to the middle of the cell and line up on the midline or equator </li></ul><ul><li>One sister chromatid from each pair points to one pole while the other points to the opposite pole </li></ul>
  7. 7. Anaphase <ul><li>The centromeres split and the sister chromatids are pulled to opposite poles of the cell </li></ul>
  8. 8. Telophase <ul><li>Chromosomes uncoil </li></ul><ul><li>Spindle is broken down </li></ul><ul><li>Nuclear envelope reappears </li></ul><ul><li>Cytokinesis begins </li></ul>
  9. 9. Cytokinesis <ul><li>Cytoplasm is split forming two daughter cells each with its own nucleus and cytoplasmic organelles </li></ul><ul><ul><li>In animals : a cleavage furrow is formed that pinches the two cells apart </li></ul></ul><ul><ul><li>In plants : a cell plate forms between the two new cells to start the formation of the cell wall (this does not occur in animal cells!) </li></ul></ul>Cell Plate
  10. 10. Name the Phase Prophase Prophase Metaphase Anaphase Metaphase Telophase Telophase Anaphase
  11. 11. Controlling the Cell Cycle <ul><li>The cell cycle is driven by a chemical control system telling the cell when to turn on and off cell division </li></ul><ul><ul><li>Internal signals – cell senses the presence of enzymes produced within the cell </li></ul></ul><ul><ul><li>External signals – cell senses the presence of chemicals (such as growth factors ) produced by other specialized cells </li></ul></ul><ul><li>Cells also respond to physical signals </li></ul><ul><ul><li>When cells are packed in too closely , division is turned off </li></ul></ul><ul><ul><li>When cells are not in contact with other cells, division is turned on </li></ul></ul>
  12. 12. Controlling the Cell Cycle <ul><li>The cycle control system is regulated at certain checkpoints </li></ul><ul><li>At each checkpoint, the cell decides if it should go on with division </li></ul><ul><ul><li>G1 – makes sure conditions are favorable and cell is big enough for division </li></ul></ul><ul><ul><li>G2 – cell checks for any mistakes in the copies of DNA </li></ul></ul><ul><ul><li>Mitosis – cell makes sure chromosomes and spindle are arranged properly </li></ul></ul><ul><li>Specific stimuli are required to initiate cell division. Cell division in most animal’s cells is in the “ off ” position when no stimulus is present </li></ul>
  13. 13. Mitosis Out of Control <ul><li>Cancer cells are an example of cells that do not listen to the cell’s control system </li></ul><ul><li>Cancer cells keep dividing even though they may be closely packed together or no growth factor is present. </li></ul><ul><li>Cancer begins as a single cell </li></ul><ul><li>This cell is normally found and destroyed by the body’s immune system. If not, this cell could divide into a mass of identical daughter cancer cells that: </li></ul><ul><ul><li>Impair the function of one or more organs – malignant tumor </li></ul></ul><ul><ul><ul><li>Cells can break off , enter the blood and lymph systems and invade other parts of the body and become new tumors . </li></ul></ul></ul><ul><ul><li>Remain at their original site – benign tumor </li></ul></ul>
  14. 14. DNA <ul><li>Deoxyribonucleic Acid (DNA) contains the information for life – all the instructions needed to make proteins (including enzymes ) </li></ul><ul><li>A segment of DNA that controls the production of a protein is called a gene . Hundreds of genes together make up a chromosome . </li></ul><ul><ul><li>DNA  genes  chromosomes </li></ul></ul><ul><li>DNA is a polymer made up of a chain of nucleotides </li></ul><ul><li>Each nucleotide has three parts: </li></ul><ul><ul><li>simple sugar (deoxyribose) </li></ul></ul><ul><ul><li>phosphate group </li></ul></ul><ul><ul><li>Nitrogen base (adenine, guanine, thymine, or cytosine) </li></ul></ul>
  15. 15. DNA Nucleotide Structure
  16. 16. DNA Structure Nucleotide Single ring nitrogen bases always bind with a double ring nitrogen base: Adenine to Thymine Cytosine to Guanine
  17. 17. Nucleotide Sequence <ul><li>The DNA of all living things has the same four nitrogen bases. </li></ul><ul><li>They are different due to the different sequences of those bases. </li></ul><ul><ul><li>For example, the code ATTGAC would code for a different protein than TCCAAA </li></ul></ul><ul><li>Because the order of these bases is so important, DNA must carefully replicate itself when the cell divides to ensure an exact copy is passed on to each daughter cell </li></ul>
  18. 18. DNA Replication <ul><li>DNA is un zipped and unwound by the enzyme helicase </li></ul><ul><li>The enzyme Polymerase attaches and reads the DNA </li></ul><ul><li>DNA nucleotides find their compliments on each side of the DNA strand </li></ul><ul><li>New bases keep attaching until two identical molecules of DNA are completed. This is called semi-conservative replication . Replication Forks increase the speed of replication. </li></ul><ul><li>Mitosis would then follow where each daughter cell would be given matching copies of the original DNA </li></ul>
  19. 19. Protein Synthesis <ul><li>Flow of genetic information-- DNA->RNA->Protein </li></ul><ul><li>DNA holds the code for protein synthesis but it cannot leave the nucleus . </li></ul><ul><li>Protein synthesis is performed at the ribosomes in the cytoplasm </li></ul><ul><li>The cell uses RNA to copy the code from DNA and bring it to the ribosomes </li></ul><ul><li>RNA (ribonucleic acid) has three parts: </li></ul><ul><ul><li>Simple sugar (ribose) </li></ul></ul><ul><ul><li>Phosphate group </li></ul></ul><ul><ul><li>Nitrogen base (adenine, cytosine, guanine, and uracil ) </li></ul></ul><ul><ul><ul><li>There is no thymine in RNA – it is replaced with uracil </li></ul></ul></ul>
  20. 20. RNA Structure
  21. 21. Transcription <ul><li>Copying the portion of DNA that carries the code for a protein is called transcription . </li></ul><ul><li>A portion of DNA that codes for a specific protein is unwound </li></ul><ul><li>RNA nucleotides find their compliment </li></ul><ul><li>DNA - ATTGCTCCG </li></ul><ul><li>RNA - UAACGAGGC </li></ul><ul><li>The RNA strand ( mRNA ) releases from the DNA strand </li></ul><ul><li>mRNA strand is edited and released from the nucleus </li></ul>
  22. 22. Transcription Chapter 10
  23. 23. Translation <ul><li>Translation is the process of interpreting mRNA to build a chain of amino acids that make up a protein </li></ul><ul><li>mRNA leaves the nucleus and heads to the ribosomes where translation will occur </li></ul><ul><li>Each sequence of three nucleotides is called a codon. </li></ul><ul><li>Each codon codes for a specific amino acid . </li></ul><ul><li>UAA CGA GGC </li></ul>codon codon codon
  24. 24. Translation Steps <ul><li>Amino acids are brought to the ribosome by tRNA </li></ul><ul><li>There are 20 different tRNA molecules, one for each type of amino acid </li></ul><ul><li>tRNA anticodons find their compliment codon on the mRNA </li></ul><ul><li>mRNA codons – UAA CGA GGC </li></ul><ul><li>tRNA atnicodons – AUU GCU CCG </li></ul><ul><li>Peptide bonds forms between the amino acids forming a polypeptide </li></ul><ul><li>Translation stops when a stop codon is reached </li></ul>tRNA
  25. 25. Translation Steps
  26. 26. Chapter 10 Genetic Code <ul><li>The nearly universal genetic code identifies the specific amino acids coded for by each three-nucleotide mRNA codon . </li></ul>The Human Genome: The entire gene sequence of the human genome , the complete genetic content, is now known. Approximately 30,000 genes .
  27. 27. Processes and Code Transfer <ul><li>Replication – copies DNA to make another identical double strand of DNA </li></ul><ul><li>Transcription – makes a copy of a section of DNA and creates a single strand of mRNA </li></ul><ul><li>Translation – reads the sequence of mRNA nucleotides to build a protein </li></ul>
  28. 28. Protein Secretion <ul><li>The polypeptide chain that is made during translation is sent to the endoplasmic reticulum (ER) for any further structural components </li></ul><ul><li>Golgi bodies package the protein and send it to the cell membrane </li></ul><ul><li>The protein is then secreted from the cell and sent where the body needs it </li></ul>http://courses.washington.edu/conj/cell/secretion.htm
  29. 29. Mutations <ul><li>If the mRNA does not copy the code correctly , the amino acid chain will be altered – this is called a mutation </li></ul>