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 Living in Our Ocean of Air How do cells replicate? Pages 1-­‐16 Date ________________________________ What you will know by the end of Challenge 2 • Why cells replicate • How cells replicate • The difference between mitosis and meiosis • How cells produce proteins Resources: Cells and Heredity pp. 61-­‐68 and 97-­‐106 Think about it: Consider the questions on page 2. In the space below, write a short paragraph that explains why cells divide and what is necessary in order for a single cell to become two complete cells. Living in Our Ocean of Air How Cells Replicate 2
Date ________________________________ Think about it: Why do cells divide? Give two reasons why a cell needs to divide. In order to prepare for a division that would result in two complete new cells, what would a cell need to do? In the cytoplasm… In the nucleus.... What happens to the DNA? Why? Living in Our Ocean of Air How Cells Replicate 3
Date ________________________________ Describe it! How does DNA double? Look carefully at the diagram and write a descriptive caption in the space under “How DNA Replicates.” How DNA Replicates What does DNA stand for? Which bases bond with each other? A = Adenine T = Thymine C = Cytosine G = Guanine What is the difference between replication and reproduction? Think about it: Use a model to demonstrate DNA replication. In your journal describe what you have discovered. Living in Our Ocean of Air How Cells Replicate 4
Date ________________________________ DNA Replication Cycle Stage-­‐ Interphase 1. Double stranded DNA duplicated 2. A chromatin strand forms 3. Chromatin gains a centromere Mitosis Phase-­‐ Prophase 4. Chromatid pair (has double DNA) Mitosis Phase-­‐ Metaphase 5. Full condensed chromosome During metaphase the spindle fibers (microtubules) attach to the centromere of the chromosome. The chromotids separate during anaphase. Consider this: Why do cells form chromosomes? Living in Our Ocean of Air How Cells Replicate 5
Date ________________________________ Describe it! Draw diagrams each phase of mitosis and write a caption that describes what happens in each phase of Mitosis. Mitosis Prophase Metaphase Anaphase Telophase During Interphase, cells grow and carry out life processes. At the end of Interphase, DNA replicates so that there are two copies of DNA. Interphase leads to Mitosis that includes Prophase, Metatphase, Anaphase and Telophase. Cytokinesis is the final stage of the Cell Cycle at the end of which two new complete cells enter Interphase. Living in Our Ocean of Air How Cells Replicate 6
Date ________________________________ Cell Cycle in Animal and Plant Cells Animal Cell Mitosis Plant Cell Mitosis Cytokinesis-­‐ Two complete daughter cells Write it up: In the space below, compare and contrast the cell cycle of the animal cell with the cell cycle of the plant cell. Living in Our Ocean of Air How Cells Replicate 7
Date ________________________________ Multiplying by Dividing-­‐ Plant Cell Cycle Follow the directions on page 9. After the activity…. Challenge Your Math Skills: Make a circle graph to show the percentage of time in each stage of the onion root tip cell cycle Cell Cycle of the Onion Root Tip Cell Living in Our Ocean of Air How Cells Replicate 8
Date ________________________________ Multiplying by Dividing Problem How long do the stages of the cell cycle take? Materials Photo of a sample of onion root tip Procedure 1. Examine the cells row by row, and count the cells that are in interphase. There should be 57 cells that can be identified as being in interphase. 2. Examine the cells row by row four more times to count the cells in prophase, metaphase, anaphase, and telophase. Record the results in the data table. Find the 2 cells that are in cytokinesis. Circle the cells that are in mitosis and cytokinesis. Data Table Stage of Cell Division Number of Cells Interphase 57 Mitosis Prophase Metaphase Anaphase Telophase Cytokinesis 2 Total Number of cells counted 64 Analyze and Conclude 1. Which stage of the cell cycle did you observe most often? 2. The cell cycle for onion root tips takes about 720 minutes (12 hours). Use your data and the formula below to find the number of minutes each stage takes. Formula Time for = Number of cells at each stage X 720 min. each stage Total number of cells counted Stage of Cell Division Minutes in each Stage % Time Interphase Mitosis Prophase Metaphase Anaphase Telophase Cytokinesis Total Number of Minutes 720 100 3. Calculate the percentage of time spent in each stage of the cell cycle. Formula for Percentage: Total time in Stage = %of time in Stage Total Time Living in Our Ocean of Air How Cells Replicate 9
Date ________________________________ Make a Protein DNA
A
T
G
C
mRNA
->
U
->
A
->
C
->
G
Got the Code?
DNA language uses four letters: A (Adenine), T (Thymine), C (Cytosine), and G (Guanine). In the nucleus, RNA reads the unzipped DNA transcribes the code using RNA complemnetary bases. RNA substitutes the letter U (Uracil) for T. An enzyme called RNA polymerase locks the RNA bases together to form messsenger RNA (mRNA). mRNA carries the code to ribosomes on the rough endoplasmic reticulum. The message is translated by transfer RNA (tRNA) into amino acid language (3 letters “spell” out an amino acid code). The amino acids are carried to the ribosome by tRNA and are snapped together to become a protein that is packaged by the golgi apparatus and shipped to whereever it is needed. Example of Transcription, Tranfer. and Translation DNA Strand A T C mRNA Strand U A G tRNA Strand A U C Amino Acid Isoleucine Living in Our Ocean of Air G C G A U A Aspartic acid How Cells Replicate 10
T A U Date ________________________________ Make a protein rRNA is ribosomal RNA, mRNA is messenger RNA, tRNA is transfer RNA image source: http://www.coolschool.ca/lor/BI12/unit6/U06L01.htm In Your Own Words Transcription is Translation is Name the Organelles The cell organelles involved in protein synthesis and packaging are: ___________________________ makes RNA ___________________________ directs the cell functions by DNA instructions ___________________________ assembles the amino acids into protein ___________________________ moves molecules through the cell ___________________________ wraps molecules in a membrane ___________________________ provides energy in the form of ATP The endoplasmic reticulum becomes rough when __________________ are attached to it. Living in Our Ocean of Air How Cells Replicate 11
Date ________________________________ Do it: Figure out how to read the code. The diagram below shows the coding for common amino acids that are the building blocks of proteins. tRNA Codon Chart Three mRNA bases form a codon. tRNA reads the codon. tRNA forms a complementary anti-­‐codon. The tRNA anti-­‐codon is translated into amino acid language. Amino acids are the monomers that form protein polymers. Notice that some amino acids have a variety of tRNA anti-­‐codons that may be the result of mutations. There are also start (AUG, methionine) and stop (UAA, UGA, or UAG) codes that tell the ribosomes to begin protein production and to end protein production. DNA triplet –> transcribed by mRNA as a codon –> mRNA leaves the nucleus -­‐> mRNA binds to a ribosome -­‐>tRNA forms an anti-­‐codon -­‐> tRNA anti-­‐codon translated to amino acids –> protein string starts Living in Our Ocean of Air How Cells Replicate 12
Date ________________________________ Do it: Make a protein using the code table. ATG in DNA means start. TAA, TGA, TAG all mean stop in DNA. Inside the nucleus: Transcribe the DNA into RNA (remember that U substitutes for T in RNA base code). Be careful, you must find the START triplet and STOP triplet. Do not code anything before the start or after the stop. If a base is not needed, put and X in the m-­‐RNA box. DNA Strand T A T G G A T C T G C T C A A G T A A G m-­‐RNA Strand Outside the Nucleus: Carry the message to the ribosomes on the rough endoplasmic reticulum in the cytoplasm. Make the tRNA complement. Carry only the triplets for amino acids. Amino Acids t-­‐RNA m-­‐RNA U A C MAKE THE PROTEIN What are the amino acids in the protein that you made? Living in Our Ocean of Air How Cells Replicate 13
Date ________________________________ Fill in the blanks…. Living in Our Ocean of Air How Cells Replicate 14
Date ________________________________ Review Body cells replicate by the process of ______________________, yielding daughter cells with a full complement of DNA. Look closely at the plant cells below. Identify the cell stage or mitosis phase of the selected cells (1, 3, 6, 8, 9, 10). 1 3 6 8 9 10 Complete the Cell Cycle Diagram for the Animal Cell. Living in Our Ocean of Air How Cells Replicate 15
Date ________________________________ Add letters to the bases along the double helix to show the complementary base pairs of DNA. A = Adenine T = Thymine C = Cytosine G = Guanine What does DNA stand for? What is the shape of DNA called? Where is DNA located? What process is shown in the diagram? Where does it occur? How is RNA different from DNA? What is m-­‐RNA? What process is shown in the diagram? What is t-­‐RNA? What organelle produces ribosomes? What do ribosomes do? Where do they do this? What are proteins made of? Living in Our Ocean of Air How Cells Replicate 16