Unit #5 - Instructions for Life: DNA. Background Image

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1 Unit #5 - Instructions for Life: DNA

2 Introduction On the following slides, the blue sections are the most important. Underline words = vocabulary! All cells carry instructions for life DNA. In this unit, we will study the basic shape of DNA and learn how the molecule DNA carries instructions for life.

3 DNA Lab Reflections What did you learn during the this week s DNA extraction lab? What surprised you? How can this science help society? DNA extraction has improved with modern science. View the video clip to understand how crime investigators collect DNA samples from evidence. Video

4 DNA Cell Review Video Link

5 Instructions Within Cells All cells have genetic material known as DNA (deoxyribonucleic acid). In prokaryotes, the DNA is loose within the cell. In eukaryotes, DNA is held within the nucleus. Regardless of where the DNA is contained in the cells, the instructions for every part of an organism come from the molecule DNA.

6 rt/modules/genome/en-images/nucleotide.gif DNA DNA stores and transmits genetic information from one generation to the next. Years of research has lead scientists to begin to understand how DNA works. DNA is made up of strings of nucleotides. Sketch it!

7 DNA = Strings of Nucleotides DNA nucleotides, or nucleic acids are made up of 3 basic components: A five-carbon sugar called deoxyribose A phosphate group A nitrogen base (A, T, C, or G)

8 Basic Structure of DNA The sugar/phosphate backbone makes up the outside of the DNA molecule. There are four nitrogen bases that make up the middle of DNA. They are Adenine: this base always pairs with thymine Guanine: this base always pairs with cytosine The bases are connected by a hydrogen bond.

9 Chargaff s Rules An American biochemist, Erwin Chargaff, studied the structure of DNA. Chargaff s rules state that within the DNA molecule, the percentage (or amount of) of guanine always matches the percentage of cytosine (they always pair together). Likewise, the %T= %A. G-CAT rule (straight letters together and curvy letters together)

10 Nucleotide Hands With a pen: Write a P on your thumb S on your palm Write an A on your 1 st finger G = 2 nd finger C = 3 rd finger T = pinkie

11 Memory Tool 1. A s pair with T s 2. G s pair with C s 3. Sugars with the Bases 4. Phosphates are free!

12 DNA Writing Prompt What is DNA? Add details to your prompt from last week: The shape? The components (or parts)? The pattern? Draw a picture for extra credit!

13 DNA Structure Chart Nucleotides Sugar Phosphate Nitrogenous Base Backbone a a X Center X X a

14 DNA s History: Franklin s XRays In the early 1950 s, Rosalind Franklin (a woman!) studied the structure of DNA using X- rays. Franklin s X-rays eventually led to the discovery that the strands of DNA are twisted around each other in a shape much like the coils of a spring, known as a helix. Video Franklin's X-ray diffraction photograph of DNA, 1953 Photo: Courtesy HarperCollins

15 DNA s History: Watson & Crick s Model Around the same time Franklin was researching DNA, two other scientists James Watson and Francis Crick were also studying DNA. They built 3-D models to show the shape of DNA using wire and cardboard. Watson and Crick s model of DNA was a double helix, where 2 strands of DNA twist around each other.

16 The Model That Started it All Reconstruction of Crick and Watson s 1953 molecular model of DNA, using the original components. Science Museum/Science and Society Picture Library

17 DNA Quick Fact If you took the DNA found in every cell of the human body and stretched it out, it would be 610 million km long. You could travel from Earth to the sun and back twice! if

18 Practice Creating the Code Pick up a white board and marker from the front. Practice making the complimentary DNA strand using the following code. A G C T A G C

19 Practice Creating the Code Pick up a white board and marker from the front. Practice making the complimentary DNA strand using the following code. A C T G A T A

20 DNA Replication DNA contains instructions for every cell of an organism. It, therefore, needs to be copied (or replicated) for each new cell to function properly. The design of DNA makes it easy to copy! Using the G-CAT rule, half a strand of DNA can easily create the complimentary strand! DNA replication is when a cell duplicates its DNA.

21 Replication Fork During DNA replication, the strand separates into two strands forming a replication fork. Enzymes (specifically DNA polymerase & helicase) help during replication and unzip the DNA molecule to create the fork. This can occur spontaneously at multiple points along the DNA strand until the entire strand has been copied D945A01.png

22 ne0000/ne0000/ /dna-replication.png DNA Polymerase DNA polymerase travels down the strand, reading each nitrogen base (A,T,C or G) and using molecules made within the cell, builds the new strand. Remember, A always with T, C always with G! (G-CAT) Each DNA molecule to go through replication has one old strand and one new strand. Video

23 Semi Conservative Model (of DNA Replication) The Semi-conservative model of DNA replication statest that each DNA molecule to go through replication has one old strand and one new strand. Video

24 The Central Dogma DNA Transcription RNA Translation PROTEIN Replication

25 Genes Contained with DNA The DNA within cells is contained within chromosomes in the nucleus. Sections of the DNA strand code for specific information, called genes. Genes code for specific traits (EX brown eyes, skin color, or blood type).

26 Genes Code for Proteins The genes within a cell s DNA code for instructions, but instructions for what? The instructions in DNA are instructions for making proteins. Proteins (large molecules) are involved in many biological functions, from making up our skin, hair, and muscles, to fighting the common cold. DNA makes the proteins that create you!

27 RNA DNA is held within the nucleus of each cell. mrna (or messenger ribonucleic acid) carries a copy of the genetic code to make proteins at the ribosomes (rrna) of the cell.

28 RNA cont. RNA is composed of: sugar called ribose a phosphate group and nitrogenous base U-A G, C Uracil (replaces Thymine) in RNA RNA is single stranded, not double like DNA There are three types of RNA (mrna, trna, and rrna). VL/GG/images/rna.gif

29 Practice Creating the Code Pick up a white board and marker from the front. Practice making the complimentary RNA strand using the following code. A C T G A T A

30 Practice Creating the Code Pick up a white board and marker from the front. Practice making the complimentary RNA strand using the following code. A C T G A T A U G A C U A U

31 Messenger RNA Messenger (mrna) is one type of RNA that carries DNA message out of nucleus to the ribosome. mrna is created in the nucleus in the process called transcription (or the process of copying genetic information from DNA into mrna). Transcription happens in the nucleus.

32 Making mrna If the DNA code reads like this ATC-GTA-CGC-AAT-TGC Then the mrna code reads like this UAG-CAU-GCG-UUA-ACG A = U G = C The enzyme RNA polymerase separates two strands of a DNA double helix and builds a strand of RNA using RNA nucleotides (A, U, C, G). Remember, RNA is a single strand. The creation of RNA is called transcription.

33 Transfer RNA or trna c/chpt15/trna.gif Transfer (trna) RNA carries amino acids to the ribosome where the proteins are built. A trna molecule is a single strand of RNA that loops back on itself. One looped end of the trna has a codon that matches the mrna codon. The other end carries an amino acid.

34 Translation yicp/protein%20synthesis.jpg The ribosome is an organelle in the cell which builds proteins. The mrna carries the code (or instructions) to the ribosome. The ribosome reads the strand three bases at a time. Three base pairs (called a codon or a triplet; EX AUG ) code for a specific amino acid; amino acids make up proteins.

35 Protein Synthesis Video Video

36 RNA Codons Molecules called amino acid chains make up proteins. Some codons do not code for amino acids, but signal a ribosome to either start or stop copying the strand. There is only one start codon (AUG) that can begin the process (methionine). UAA, UAG and UGA are 3 stop codons (like a period at the end of a sentence) which tell the ribosome the protein is complete.

37 AA Chart An amino acid chart helps to translate codons. Start at the center and pick a letter. Move to the next level and pick another letter. Finally move to the outside and the three letters (a codon ) match up to an amino acid (found on the outside!). Practice: GGA codes for.?

38 Translation = Building a Protein Translation occurs when the cell uses the genetic information in mrna to build proteins. Translation is done at the ribosome (the site of protein synthesis). mrna comes from the nucleus and binds to the ribosome. the start codon AUG signals the beginning of a protein. trna molecules carry specific amino acids from around the cytoplasm to the ribosome. As each trna molecule arrives with an amino acid, it links it to the previous amino acid that was dropped off there, forming a long chain.

39 Protein Synthesis (a protein) Protein Synthesis Animation

40 _at_ribosomes.gif In Conclusion All cells (prokaryotes & eukaryotes) contain DNA! The role of DNA is like the master plan that a builder would use to construct a house. The role of RNA is like the inexpensive blueprints that are taken to the construction site (mrna & trna). The DNA (master plan) must be stored safely in the nucleus while RNA can leave the nucleus to go to the protein-building site. The protein building site is the ribosome.