Slide 32 / 155 Watson and Crick's Double Helix Using information from the work of Wilkins and Franklin, James Watson and Francis Crick were the first to propose the double helical nature of DNA. Francis Crick is also well known for coining the term "central dogma" regarding the flow of genetic information from DNA to RNA to protein. The day they discovered the helix in 1953, they are said to have left their lab, walked into a pub in Cambridge, England and interrupted the patrons' lunchtime shouting " we have discovered the secret to life !"
Slide 33 / 155 Double Helix
Slide 34 / 155 7 The scientists associated with the discovery of the structure of DNA were: A Hershey and Chase B Watson, Crick, Wilkins, and Franklin C Avery, MacLeod, and McCarty
Slide 35 / 155 8 These scientists showed that DNA was at the root of bacterial transformation. A Hershey and Chase B Watson, Crick, Wilkins, and Franklin C Avery, MacLeod, and McCarty
Slide 36 / 155 9 Four of the following terms all involve the experiment of Hershey and Chase. Choose the one which does not belong. A helix structure B DNA C virus D host E bacteriophage
Slide 37 / 155 DNA DNA is made up of two chains of repeating nucleotides. 1 Nucleotide
Slide 38 / 155 DNA
Slide 39 / 155 Deoxyribonucleic Acid DNA is a good archive for genetic information since the bases are protected on the inside of the helix.
Slide 40 / 155 10 If one strand of DNA is CGGTAC, the complementary strand would be: A GCCTAG B CGGTAC C TAACGT D GCCATG
Slide 41 / 155 11 Four of the following are associated with DNA. Choose the one which is not. uracil A thyamine B adenine C guanine D cytosine E
Slide 42 / 155 12 If one strand of DNA is AGCTGA, the complementary strand would be: A TCGACU B TCGACT C AGCTGA D AGTCGA
Slide 43 / 155 Replication The functions of a cell are determined by its DNA. Cells have to reproduce many times. In complex organisms, trillions of copies are made from one original cell. But when cells reproduce, their DNA has to reproduce as well. The structure of DNA reveals how trillions of copies of the DNA in one of your cells can be made, and be nearly identical each time.
Slide 44 / 155 Replication Consider these three facts: · Each individual strand of DNA is held together by strong covalent bonds. · The two strands are held to one another by weaker hydrogen bonds. · Each base (ACGT) attracts only its complementary base (TGCA)
Slide 45 / 155 DNA Molecule as Template template Each molecule of DNA is made strand of a template strand and a new strand. The template is used to make the new strand. The template strand is also known as the parent strand since it came from the original DNA molecule. The new strand is also known as the daughter strand .
Slide 46 / 155 Replication DNA nucleotide monomers are made ahead of time and stored in the cell. When it is time for the DNA to replicate itself, the nucleotides are ready to be added to the new growing strand of DNA. DNA polymerase is the enzyme responsible for adding each new nucleotide to the growing strand.
Slide 47 / 155 Replication DNA is anti-parallel. Each strand has two ends: a 5' end and a 3' end. Nucleotides can only be added to the -OH end (3`), not the 5` so all strands grow from the 5' end to the 3' end. Each molecule of DNA is made of one "old" and one "new" strand. The "old" strand is used as a template to make the "new" strand.
Slide 48 / 155 Semi-Conservative DNA Replication The template strands of the DNA molecule separate and the new strands are made on the inside. The new strands are made in the 5' - 3' direction. The result of this process is 2 new DNA molecules each having an old template strand and new strand.
Slide 49 / 155 Semi-Conservative DNA Replication Two parent strands One parent and One parent and one daughter one daughter strand strand
Slide 50 / 155 Semi-Conservative Replication DNA replication is said to be a Semi-Conservative process. This means that the template DNA strand is partially saved and reused throughout the process. The base sequence on the template strand will allow for the creation of the base sequence on the new strand. 3' ATCGGGTTAACGCGTAAA 5' template strand 5' ______________________ 3' new strand What is the sequence of the new strand?
Slide 51 / 155 13 The 3' end of a DNA strand has a phosphate at the end. True False
Slide 52 / 155 14 Why does a DNA strand only "grow" in the 5' to 3' direction? A because DNA can only add nucleotides to the 3' end of the molecule because DNA can only add nucleotides to the 5' B end of the molecule because mRNA can only read a DNA molecule C from 5' to 3' because mRNA can only read a DNA molecule D from 3' to 5'
Slide 53 / 155 15 If the parent DNA strand is 5' ATCGATACTAC 3', what will the daughter stand be A 5' TAGCTATGATG 3' B 3' ATCGATACTAC 5' C 5' UAGCUAUGAUG 3' D 3' TAGCTATGATG 5'
Slide 54 / 155 16 "Semi-conservative" means: A the DNA is used slowly B the DNA is sometimes reused C the DNA is partially saved and reused in the process D only part of the DNA is used
Slide 55 / 155 17 Which of the following is a nucleotide unit found in DNA? A ribose + phosphate + thymine B deoxyribose + phosphate + uracil C deoxyribose + phosphate + cytosine D ribose + phosphate + uracil
Slide 56 / 155 DNA Replication Return to Table of Contents
Slide 57 / 155 DNA Replication In-Depth In order for DNA replication to occur, DNA strands, which are naturally twisted in the shape of a double helix, must be relaxed, unwound, and opened-up to allow each strand to be copied. Then nucleotides must be added to each strand. Many enzymes are involved in this process.
Slide 58 / 155 DNA Replication In-Depth Topoisomerase binds to the DNA strand and cuts the double helix, causing the molecule to untwist and relax.
Slide 59 / 155 DNA Replication In-Depth Helicase breaks hydrogen bonds between nucleotide base pairs causing the two strands to separate and form a replication fork . Small proteins called single-stranded binding proteins stabilize each strand.
Slide 60 / 155 18 Which enzyme causes the double helix to unwind by breaking hydrogen bonds? Topoisomerase A Helicase B Polymerase C RNAse D
Slide 61 / 155 DNA Replication In-Depth Recall in a DNA molecule, DNA strands are antiparallel, meaning that one strand runs from the 3' OH group at one end of the molecule to 5' phosphate group at the other end of the molecule. The other strand runs in the opposite direction from 5' to 3'. At the replication fork, the new strand added in the 5' to 3' direction is referred to as the leading strand . The new strand added in the 3' to 5' direction is called the lagging strand . 3' 5'
Slide 62 / 155 DNA Replication In-Depth On the leading strand, new complementary nucleotides are added continuously by the enzyme DNA polymerase . *DNA polymerase can only add nucleotides to the 3' end of a parent strand, so the leading strand elongates toward the replication fork in the 5' to 3' direction.
Slide 63 / 155 19 DNA Polymerase adds nucleotides in which direction? 3' to 5' A 5' to 3' B 3' to 5' and 5' to 3' C 5' to 5' D
Slide 64 / 155 DNA Replication In-Depth The lagging strand elongates away from the replication fork. DNA polymerase cannot add nucleotides to the end of this parent strand continuously, and the process of adding nucleotides discontinuously becomes a bit more complicated.
Slide 65 / 155 DNA Replication In-Depth First an enzyme called DNA primase synthesizes a short RNA primer - a complimentary sequence of RNA that binds to the DNA on the lagging strand.
Slide 66 / 155 DNA Replication In-Depth The RNA primer allows DNA polymerase to bind and add short segments of nucleotides called Okazaki fragments . Okazaki fragments are between 100-200 nucleotides long in eukaryotes and about 1000-2000 nucleotides long in prokaryotes. 5' 3'
Slide 67 / 155 DNA Replication In-Depth The short Okazaki fragments are joined together by the enzyme DNA ligase to produce a continuous strand. 3' 5' Click Here for Animation
Slide 68 / 155 20 In this diagram, the highlighted arrows are pointing to The leading strand A DNA Polymerase B Okazaki Fragments C DNA Ligase D
Slide 69 / 155 21 The green dot represents which enzyme? Helicase A Ligase B DNA Primase C DNA Polymerase D
Slide 70 / 155 22 The highlighted arrow is pointing to the Parent strand A Leading strand B Lagging strand C Okazaki fragment D
Slide 71 / 155 23 The highlighted arrow is pointing to the Lagging strand A Leading strand B Replication fork C Replication bubble D
Slide 72 / 155 DNA Replication In-Depth Lagging and leading strands grow simultaneously resulting in the formation of two new DNA molecules. Click Here for Animation
Slide 73 / 155 DNA Replication In-Depth Write the name of the enzyme that matches the description. Cuts double helix to Breaks H bonds, prepare for replication unwinding DNA strands Adds nucleotides to Synthesizes RNA parent strand Primer Short pieces of nucleotides Brings together added to lagging strand Okazaki fragments
Slide 74 / 155 DNA Replication In-Depth DNA replication begins at specific sites on a chromosome called origins of replication and can occur at many different places on a chromosome simultaneously. Click Here for Animation
Slide 75 / 155 24 DNA replication is initiated at The origin of replication A One site at a time B The edges of a chromosome C The lagging strand D
Slide 76 / 155 RNA Transcription Return to Table of Contents
Slide 77 / 155 DNA to RNA We stated earlier in this chapter that the functions of a cell are determined by DNA, and this is true. But DNA cannot function by itself...it needs the help of RNA.
Slide 78 / 155 RNA RNA is essential for bringing the genetic information stored in the DNA to where it can be used in the cell. Recall that RNA is made up of a sugar molecule and phosphate group "backbone" and a sequence of nitrogen bases: Adenine (A) Uracil (U) Guanine (G) Citosine (C) These bases hydrogen bond in pairs: A bonds to U and G bonds to C.
Slide 79 / 155 25 RNA is more stable than DNA. True False
Slide 80 / 155 Transcription Transcription is the process by which RNA strands are synthesized from DNA strands. This is the first step in the transport of the genetic information contained in DNA. The process of making RNA from DNA is called transcription because the DNA sequence of nucleotides is being rewritten into the RNA sequence of nucleotides, which differ only slightly. The process of transcription is very similar to that of DNA replication.
Slide 81 / 155 Transcription In DNA replication both strands are used as templates. Which DNA strand is used to make RNA?
Slide 82 / 155 Transcription: DNA Strands One of the DNA strands has the code for the protein that will be made from RNA; that code is called the gene. The strand with the genes is called the " non-template strand ." This IS NOT the strand that is transcribed. The other strand is the mirror image of the first, it carries the mirror image of the gene, not the gene itself. It is called the " template strand ." This IS the strand that gets transcribed into RNA.
Slide 83 / 155 Transcription: DNA Strands This makes sense in that the RNA will be the mirror image of the DNA it is transcribed from. And the non-coding strand is the mirror image of the gene. non-template strand of DNA template strand of DNA transcription of template strand RNA Note: the non-template strand of DNA (the gene) matches the new RNA strand
Slide 84 / 155 DNA Strands template strand non-template strand
Slide 85 / 155 Transcription Transcription proceeds along the DNA molecule, coding an RNA molecule. The RNA molecule is always made from the end with a phosphate group towards the end with a hydroxyl group. Just like in DNA replication, RNA is made from the 5' end to the 3' end.
Slide 86 / 155 Transcription Transcription is made possible by the fact that the different bases are attracted to one another in pairs. RNA DNA A bonds with T U bonds with A G bonds with C C bonds with G
Slide 87 / 155 Replication vs Transcription DNA Replication Transcription Two new double-stranded One new single-stranded DNA are produced RNA is produced Adenine from the parent Adenine on the DNA strand bonds with thymine strand bonds with uracil on on the new daughter the new RNA strand. strand of DNA Only the strand with the The whole DNA molecule code for the gene is is replicated transcribed. Synthesis of both occur in the 5' to 3' direction
Slide 88 / 155 26 What was the first genetic storage molecule? A DNA B protein C RNA D amino acid
Slide 89 / 155 27 What molecule is now used to store genetic information? DNA A protein B RNA C D amino acid
Slide 90 / 155 28 The strand that is transcribed into RNA is called the A Template Strand Non Template Strand B RNA Strand C Amino Acid Strand D
Slide 91 / 155 29 The strand that is NOT transcribed into RNA is called the A Template Strand Non Template Strand B RNA Strand C Amino Acid Strand D
Slide 92 / 155 30 Genes are located on the A Template Strand Non Template Strand B RNA Strand C Amino Acid Strand D
Slide 93 / 155 Steps of Transcription Initiation Elongation Termination
Slide 94 / 155 Step 1 - Initiation An enzyme called RNA Polymerase attaches to the promoter sequence on the DNA. The Promoter is a specific sequence of bases that the RNA polymerase recognizes. olymerase Non- Template Promotor Region
Slide 95 / 155 Step 2- Elongation RNA Polymerase synthesizes the new RNA by moving down the DNA template strand reading the bases and bringing in the new RNA nucleotides with the proper complementary bases. As the RNA Polymerase runs down the DNA, it actually unwinds the DNA! Non- Template new mRNA
Slide 96 / 155 Step 3 - Termination RNA Polymerase gets to a sequence on the DNA called a Termination Sequence . This sequence signals the RNA Polymerase to STOP transcription. olymerase Non- Template Termination Sequence The RNA Polymerase falls off the DNA. The new RNA strand separates from the DNA and the DNA recoils into a helix. Click Here to see an animation of Transcription
Slide 97 / 155 31 The transfer of genetic material from DNA to RNA is called: A translation B transcription C elongation D promotion
Slide 98 / 155 32 What is the function of the promoter sequence on the DNA? it is where the RNA polymerase recognizes and binds A to initiate transcription it is where the RNA gets copied B it is where the RNA polymerase binds to on the 5' end C of the DNA initiating transcription it is where the RNA polymerase binds to on the 3' end D of the DNA initiating transcription
Slide 99 / 155 33 If the template strand of DNA is 5' ATAGATACCATG 3', which is the RNA strand produced from transcription A 5' UAUCUAUGGUAC 3' B 5' TATCTATGGTAC 3' C 3' UAUCUAUGGUAC 5' D 3' TATCTATGGTAC 5'
Slide 100 / 155 34 If the non-template strand of DNA is 3' ACGATTACT 5', which is the RNA strand produced through transcription A 3' TGCTAATGA 5' B 3' UGCUAAUGA 5' C 5' UGCUAAUGA 3' D 5' ACGAUUAGU 3'
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