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84 Cards in this Set
- Front
- Back
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Who discovered the shape of the DNA molecule?
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Watson and Crick
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What year was the shape of the DNA molecule discovered?
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1953
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What is the shape of the DNA molecule?
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double helix
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What does the double helix resemble?
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a twisted ladder
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What are the monomers or sub units of DNA called?
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nucleotides
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What are the three parts of a nucleotide?
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a phosphate, a deoxyribose or sugar molecule, and a nitrogenous base
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What are the 4 nitrogenous bases of the DNA molecule?
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adenine,
thymine, cytosine, guanine |
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What does DNA stand for?
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deoxyribonucleic acid
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Why are there 4 different nucleotides?
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because there are 4 different nitrogenous bases
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Which bases are the purine and how many carbon rings do they have?
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Adenine and Guanine, two carbon rings
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Which bases are the Pyrimidines and how many carbon rings do they have?
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thymine and cytosine have one carbon ring each
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Where in the DNA molecule do the bases bond, and what part of the ladder is that bond?
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the middle and the rungs
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What does adenine bond with?
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thymine A(2) T(1)
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How many adenines are in a molecule of DNA?
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5
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How many thymines are in a molecule of DNA?
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5
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What does guanine bond with?
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cytosine
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How many guanine molecules are there in a molecule of DNA?
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7
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How many cytosine molecules are in a molecule of DNA?
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7
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What is the matching of the bases called?
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complementary
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What parts of the nucleotides create the bond?
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the phosphate of one nucleotide bonds with the sugar of the other nucleotide below it, while the bases are attached to the deoxyribose sugar.
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What is the bond between the bases?
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weak hydrogen bonds
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How many hydrogen bond C & G?
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3
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How many hydrogen bond A and T?
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2
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What make up the sides of the twisted ladder?
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phosphates and sugars
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What make up the rungs of the ladder?
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bases
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The sugar phosphate backbones run in opposite directions which is called:
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antiparallel
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Because of the antiparallel structure, the DNA molecule has how many prime at each end?
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3' and 5' which refer to the number of carbon on the deoxyribose
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What does the 3' end bond to?
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the hydroxyl group (OH)
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What does the 5' end bond to?
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a phosphate
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What did the American scientist, Erwin Chargaff discover?
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There is always the same amount of A nucleotides as there are T nucleotides; and the same amount of G nucleotides as C nucleotides.
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What is the Chargaff rule?
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Chargaff's rules state that DNA from any cell of all organisms should have a 1:1 ratio of pyrimidine and purine bases and, more specifically, that the amount of guanine is equal to cytosine and the amount of adenine is equal to thymine.
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What did Rosalind Franklin do?
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She took X-ray crystallography images of DNA.
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What did Maurice Wilkins, a British scientist, do?
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Wilkins worked closely with Franklin.
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What does DNA do during the S phase of interphase?
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makes a copy of itself during DNA synthesis
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Why does the DNA replicate itself?
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So that the daughter cells will have the same amount and type of DNA.
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DNA replication is called:
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complementary base pairing
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Is DNA replication conservative, semiconservative or dispersive, and why?
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DNA replication is semiconservative because it produces molecules with both old and new DNA, but each molecule would be composed of one old strand and one new one.
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What is conservative replication?
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Conservative replication would leave intact the original DNA molecule and generate a completely new molecule.
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What is dispersive replication?
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Dispersive replication would produce two DNA molecules with sections of both old and new DNA interspersed along each strand.
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Who purified S-bacteria to isolate its components?
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Avery, MacCarty and MacLeod in 1944
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What are the components of DNA that were isolated?
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lipids, DNA, protein, carbohydrates
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What did they do with the components of S bacteria and why?
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Injected it into live S bacteria, to transform it to an S bacteria.
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What component worked?
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DNA
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Who answered the question of DNA vs protein as the genetic material in 1952?
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Martha Chase and Alfred Hershey
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What is a bacteria phage?
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a type of virus that infects and kills bacteria cells by injecting its genetic material into the bacteria and taking it over.
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What is a bacteria phage made of?
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DNA and protein
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What did Chase and Henley do to the protein coat of the bacteria phage to make it stand out from the DNA?
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they made the protein coat radioactive with 35S, sulfur
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How did Chase and Henley knock the phages off the bacteria?
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with a blender
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Who answered the question of DNA vs protein as the genetic material in 1952?
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Martha Chase and Alfred Hershey
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What is a bacteria phage?
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a type of virus that infects and kills bacteria cells by injecting its genetic material into the bacteria and taking it over.
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What is a bacteria phage made of?
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DNA and protein
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What did Chase and Henley do to the protein coat of the bacteria phage to make it stand out from the DNA?
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they made the protein coat radioactive with 35S, sulfur
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How did Chase and Hershey knock the phages off the bacteria?
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with a blender
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What did Hershey and Chase use to separate the bacteria from its surrounding liquid?
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a centrifuge
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Which separated part was radioactive?
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the liquid which held the protein was radioactive
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What did Chase and Henley use to make the DNA radioactive?
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32p, phosphorous
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What was not radioactive when the experiment was repeated with the radioactive DNA?
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the liquid with the protein
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When was DNA discovered and where was it?
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In 1868 by a Swedish scientist who found it in the cell's nucleus.
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What are chromosomes made of?
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protein and DNA
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What did Frederick Griffith do in 1928?
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In 1928, Frederick Griffith performed an experiment using pneumonia bacteria and mice. Streptococcus pneumoniae or S. pneumoniae
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What does virulent mean?
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deadly
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What was different about the two strains of bacteria Griffith used?
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He used two strains of Streptococcus pneumoniae: a “smooth” strain which has a polysaccharide coating around it that makes it look smooth when viewed with a microscope, and a “rough” strain which doesn’t have the coating, thus looks rough under the microscope.
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What happened when Griffith injected live S strain into mice?
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the mice contracted pneumonia and died.
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What happened when Griffith injected live R strain, a strain which typically does not cause illness, into mice?
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as predicted they did not get sick, but lived.
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What happened when Griffith Griffith then used heat to kill some of the S strain bacteria and injected those dead bacteria into mice?
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This failed to infect/kill the mice, indicating that the polysaccharide coating was not what caused the disease, but rather, something within the living cell.
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What happened when Griffith injected another group of mice with a mixture of heat-killed S and live R.
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the mice died
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What did Griffith's experiments indicate?
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The live R strain bacteria must have absorbed genetic material from the dead S strain bacteria, and since heat denatures protein, the protein in the bacterial chromosomes was not the genetic material
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What is the process of transformation in bacteria?
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Transformation occurs when bacteria is changed from one from to another by taking in genetic material from an outside source.
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What does helicase do during DNA replication?
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During DNA replication, DNA helicases unwind DNA at positions called origins where synthesis will be initiated. DNA helicase continues to unwind the DNA forming a structure called the replication fork, which is named for the forked appearance of the two strands of DNA as they are unzipped apart.
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Where in the cell does transcription take place?
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RNA transcription occurs in the nucleus,
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What type of enzyme unzips DNA?
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helicase
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What type of enzyme matches the free floating nucleotides to the DNA template?
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DNA polymerase
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What happens to the DNA used in transcription after the RNA has been made?
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It becomes a double strand again when DNA ligase binds the template strand back to it's complementary strand.
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How does translation begin?
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A large and small ribosomal subunit, along with the initiating tRNA assemble onto the mRNA.
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In prokaryotes, what type of sequence correctly positions the ribosome and mRNA?
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Two RNA elements correctly position the ribosome at the initiation codon.
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What does a Shine-Delgarno sequence do?
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It pairs with the 3' end of 168 rRNA.
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When does elongation begin?
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When the initiator tRNA is placed at the P site of the ribosome.
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Which site on the ribosome is where the first tRNA bonds?
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the P site
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Which site on the ribosome is where the second tRNA bonds?
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the aminoacyl-tRNA enters the ribosome at the A site
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What happens to the amino acid at the P site and what does it allow the ribosome to do?
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The amino acid at the P site is transferred to the tRNA at the A site. The ribosome moves one codon farther along the mRNA releasing the empty RNA which frees the A site for the next incoming tRNA.
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What bdoes the bonding and releasing of the tRNAs and amino acids result in?
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A growing peptide chain.
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What triggers the termination of translation?
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Translation termination is triggered by a stop codon in the mRNA.
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What is the function of th release factors?
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The release factors help release fully synthesized polypeptide chains from the ribosome.
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How does translation end?
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Translation ends with the dissociation of the ribosomal subunits.
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