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Chapter 12 Test Study Guide: Molecular Genetics and DNA
Abdulaziz AlObaidi
Test date: Monday January 16 2023
Format: MCQ, Labeling, Short Answers, Matching
Chapter 12 Section 1 and 2: DNA Structure and
Replication
Powerpoint Link
Vocabulary : Quizlet
DNA:
deoxyribonucleic acid, a self-replicating material present in nearly all living organisms. It is the carrier of genetic information. Watson and Crick: discovered the structure of DNA Roslind Franklin: Woman who generated x-ray images of DNA, she provided Watson and Crick with key data about DNA Erwin Chargaff:discover ed that A=T and G=C DNA Structure: DNA is like a ladder or spiral staircase. The outside is made of a sugar-phosphate backbone with alternating sugars and phosphates and the inside "steps" are the nitrogenous bases. RNA: a single stranded nucleic acid Nucleotide: organic molecule made up of a nitrogenous base, pentose sugar and phosphate Nitrogen Base : Adenine, Thymine, Guanine, Cytosine Purine: a nitrogenous base that has a double-ring structure; either adenine or guanine Pyrimidine: a nitrogenous base that has only one ring structure. cytosine, thymine, uracil Monomer: DNA’s monomer nucleotide; small organic molecules that make up polymers.
Semi-conservative replication: in each new DNA double helix, one strand is from the original molecule, and one strand is new DNA replication: The process in which DNA makes a duplicate copy of itself. Hydrogen bonds in DNA:A weak chemical bond that holds together the two complementary strands of DNA. Leading Strand: a single DNA strand that, during DNA replication, is replicated in the 3' - 5' direction (same direction as the replication fork). DNA is added continuously, one complementary base at a time. Lagging Strand: During DNA replication, it is replicated in the 5′ - 3′ direction (opposite direction to the replication fork). DNA is added to in discontinuous chunks called 'okazaki fragments' that are glued together through ligase Helicase: An enzyme that untwists the double helix of DNA at the replication forks. DNA polymerase:an enzyme that uses a single strand of DNA as a template to assemble a new strand by adding complementary nitrogen bases Ligase: An enzyme that connects two fragments of DNA to make a single fragment Primase:an enzyme that makes short RNA sequences called primers, which serve as starting points for DNA synthesis. Okazaki fragments: Small fragments of DNA produced on the lagging strand during DNA replication, joined later by DNA ligase to form a complete strand. Replication Fork:a Y-shaped point that results when the two strands of a DNA double helix separate so that the DNA molecule can be replicated DNA orientation: Antiparallel 3'-5' and 5'-3', direction determined by orientation of sugar
4. What are the differences between purines and pyrimidines?
Purines: Pyrimidines:
Large Small
Contain 2 carbons, 2 hydrogens, & 2
nitrogen rings
Contain 1 carbon, 1 hydrogen, 1 nitrogen
Adenine and Guanine Cytosine and Thymine
5. Know Erwin's chargaff's base pairing rules
- Amount of Adenine = Thymine ( Apple Tree)
- Amount of Cytosine = Guanine ( Car Garage )
6. How did Rosland Franklin and Erwin Chargaffs work help Watson and Crick
with their research?
Chargaff’s work helped as they were able to identify the bond between purines and
pyrmidines , and Franklin’s xray allowed them to see how the backbone looked like.
7. What phase of the cell cycle does DNA replication happen?
- DNA replication occurs in interphase in its S phase.
8. State the four enzymes and their role in DNA replication
● Helicase (“ the unzipping enzyme”): unwinds the double helix, by breaking
hydrogen bonds which later forms a replication fork.
● Primase (“ the initializer”): generates RNA primers.
- RNA primers act as templates to place the new complementary
nitrogenous bases.
● DNA Polymerase ( “ the builder”): places new nitrogenous bases.
● Ligase (“ the gluer”): joins Okazaki fragments together
9. What is the difference between the leading and the lagging strand?
Leading strand: Lagging strand:
3’ to 5’ (toward replication fork) 5’ to 3’ ( against replication fork)
Goes through continuous replication Goes through discontinuous replication
Does not require ligase Require ligase to join up Okazaki
fragments
10. Explain how the leading and lagging strands are replicated.
Leading strand: (Continuous Replication)
1. Helicase unwinds the double helix.
2. Primase lay templates for new nitrogenous bases.
3. DNA polymerase builds new strands by adding complementary nitrogenous
bases continuously. ( 5’ to 3’)
Lagging Strand: ( Discontinuous Replication)
1. New RNA primers are added (on lagging), as the replication fork continues.
2. DNA polymerase adds the complementary nitrogen bases forming Okazaki
fragments.
3. Ligase fills up the spaces in between the Okazaki fragments.
Result of Replication: (Semi-conservative replication): A strand from the original
DNA and a strand from the new copied.
11. Explain the difference between DNA and RNA
DNA RNA
Sugar Deoxyribose Ribose
Strands Two strands One strand
Size Long Short
Replication Can self-replicate CANNOT self-replicate
to 5 prime direction Nontemplate strand : the strand of DNA that is not used to transcribe mRNA; this strand is identical to the mRNA except that T nucleotides in the DNA are replaced by U nucleotides in the mRNA Polypeptide chain : A chain of amino acids linked together by peptide bonds. Central Dogma: information is transferred from DNA to RNA to protein Gene Expression: process by which a gene produces its product and the product carries out its function Transcription initiation :RNA polymerase attaches to the promoter region of DNA strand, and synthesis begins Translation initiation:in this stage, the ribosome gets together with the mRNA and the first tRNA so translation can begin. Transcription elongation :mRNA is assembled by adding nucleotides complementary to DNA template strand - DNA rewinds once read Translation elongation :tRNAs carry amino acids to ribosome and attach according to mRNA Transcription termination:When RNA polymerase reaches terminator, transcription stops & RNA chain is released Translation termination: Ribosome reaches a stop codon on mRNA (UAG, UAA, or UGA) Protein: -perform most of cell's functions -serve as building blocks for cell structures -form enzymes that catalyze the cell's chemical reactions -regulate activity of genes -enable cells to move and communicate w/ each other Protein folding:Process by which a protein structure assumes its functional shape. Protein Synthesis :is process by which the genetic code puts together proteins in the cell. Ribosome :organelle that makes protein
Topics To Know
- Compare the three types of RNA and know their role in protein synthesis. Name mRNA ( Messenger RNA) rRNA ( Ribosomal RNA) tRNA ( Transfer RnA Function -Carries genetic info from DNA for assembly of amino acids. -Combines with protein to make a ribosome. -Transfers amino acids to ribosomes during protein synthesis
- Know the steps of protein synthesis. Transcription:- Process of making a mRNA from a DNA template strand in the nucleus.
- Initiation: ● RNA polymerase binds to DNA at the promoter and unzips DNA molecule
- ( Promoter gene tells RNA polymerase where to start transcription)
- Elongation ● RNA polymerase moves along the template strand ( 3’ to 5’) adding complementary RNA nucleotides in (5’ to 3’)
- Strand that is read is called template strand
- Strand that is not read called non-template
- Termination ● RNA polymerase reaches terminator sequence , transcription stops & RNA strand is released Result: mRNA is formed and exits the nucleus to go to the ribosome (cytoplasm)
- During what stage of the cell cycle does protein synthesis happen? Protein Synthesis occurs during interphase in its Growth 1 (G1) Phase.
- Understand what happens in initiation, elongation and termination of both transcription and translation ( DONE)
- Understand RNA processing before translation ( DONE)
- Understand how to read the codon chart.
- To find out the amino acid, you must first look at the mRNA, for every three nitrogen base there is one amino acids, count three letters then see what your amino acid is.
- Understand how changes in DNA/mutations may result in a different protein shape and how this might affect the proteins function Changes in DNA/mutations may result in in a different protein shape and this may affect the protein function by the following:
- May not change protein function at all, same amino acids many codes.
- May stop the protein from fully forming by adding a stop codon too early.
- May mix up the codons which may lead to function changes.
- May remove a codon that makes proteins more efficient.
- May add an extra codon that creates a useless or harmful protein. Hyper Cholesterolemid: (Autosomal Dominant): too much cholesterol in blood which restrics blood. Diabtes:( Autosomal Recessive) body cant make enough insulin, so body can’t regulate sugar. Thalassemia( Autosomal Recessive) : body can’t make enough hemoglobin. ( cant transport O2) Down Syndrome: ( Autosomal recessive) extra chromosome, retardness. Huntington’s Disease ( Autosomal Dominant): stops brain working Sickle Cell Anemia ( Autosomal Recessive) : hemoglobin is crooked Cleft Lip ( Autosomal Dominant) : tissue in lip not fully formed Duchenne Huscular Dystrophy: (X-linked recessive): loss of muscle Dwarfism(Autosmomal Dominant): lack of growth in skeleton system Fragile X Syndrome (X-linked Dominant) : causes developmental problems. Galactosomia ( Autosomal Recessive): cannot eat galactsose ( sugar and dairy) Hemophilia:( X-linked dominant) blood does not clot Color Blindness: ( X-linked Recessive) color blind.
Genetic Diseases NOT SURE
- Hyper Cholesterolemid: (Autosomal Dominant): too much cholesterol in blood which restrics blood.
- Diabtes:( Autosomal Recessive) body cant make enough insulin, so body can’t regulate sugar.
- Thalassemia( Autosomal Recessive) : body can’t make enough hemoglobin. ( cant transport O2)
- Down Syndrome: ( Autosomal recessive) extra chromosome, retardness.
- Huntington’s Disease ( Autosomal Dominant): stops brain working
- Sickle Cell Anemia ( Autosomal Recessive) : hemoglobin is crooked
- Cleft Lip ( Autosomal Dominant) : tissue in lip not fully formed
- Duchenne Huscular Dystrophy: (X-linked recessive): loss of muscle
- Dwarfism(Autosmomal Dominant): lack of growth in skeleton system 10.Fragile X Syndrome (X-linked Dominant) : causes developmental problems.
- Galactosomia ( Autosomal Recessive): cannot eat galactsose ( sugar and dairy) 12.Hemophilia:( X-linked dominant) blood does not clot 13.Color Blindness: ( X-linked Recessive) color blind.
