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177 Cards in this Set
- Front
- Back
- 3rd side (hint)
What two individuals co-created the double-helical model for DNA?
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Francis Crick and James Watson
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____ is encoded in DNA and reproduced in all cells of the body.
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Hereditary information
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What are the two components of chromosomes?
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DNA and protein
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Who showed that genes are located on chromosomes?
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T. H. Morgan's group
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The key factor in determining the genetic material was choosing appropriate _____ ______.
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Experimental organisms.
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The role of DNA in heredity was first discovered by studying ____ and the ____ that affect them.
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Bacteria; viruses.
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The discovery of the genetic role of DNA began with research by ______ _____ in 1928.
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Frederick Griffith.
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Griffith worked with two strains of bacteria, one ____ and one ______.
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Pathogenic; harmless.
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When he mixed heat-killed remains of the pathogenic strain with living cells of the harmless strain, some living cells became _____.
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Pathogenic.
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______ is a change in genotype and phenotype due to assimilation of foreign DNA.
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Transformation.
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In 1944, who performed an experiment using heat to inactivate DNA, RNA, and proteins to conclude that DNA was the transforming substance?
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Oswald Avery, Maclyn McCarty, and Colin MacLeod.
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Only ____ worked in transforming harmless bacteria into pathogenic bacteria.
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DNA.
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T or F: Biologists remained skeptical in conclusions drawn, mainly because little was known about DNA.
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True.
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_____ are such viruses that are widely used in molecular genetic research.
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Bacteriophages (or phages).
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In 1952, who performed experiments showing that DNA is the genetic material of a phage known as T2?
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Alfred Hershey and Martha Chase.
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During infection, experiments showed that only one of the components of ____ enters an E. coli cell.
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T2 (DNA or protein).
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In experiments with T2 in E. coli, the ______ DNA of the phage provides the genetic information.
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Injected.
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What three nucleotides is the polymer DNA made of?
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Nitrogenous base, pentose (sugar), and a phosphate group.
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In 1950, who reported that DNA composition varies from one species to the next?
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Erwin Chargaff.
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Evidence of diversity made ___ a more credible candidate for the genetic material.
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DNA.
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_____ rules state that in any species there is an equal number of A nad T bases, and an equal number of G and C bases.
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Chargaff's.
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Who used a technique called x-ray crystallography to study molecular structure?
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Maurice Wilkins and Rosalind Franklin.
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Rosalind Franklin produced a picture of the DNA molecule using what technique?
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X-ray crystallography.
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Who was able to deduce that DNA was helical, width of the helix, and the spacing of the nitrogenous bases?
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James Watson.
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The width suggested that the DNA molecule was made up of two strands, forming a _____ _______.
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Double helix.
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_____ had concluded that there were two antiparallel sugar-phosphate backbones, with the nitrogenous bases paired in the molecule's interior.
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Rosalind Franklin.
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T or F: The nitrogenous bases of DNA pair like-with-like to result in a uniform width.
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False. Pairing a purine with a pyrimidine resulted in a uniform width consistent with the x-ray.
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What is a purine?
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Nitrogenous base found in nucleotides, characterized by a six-membered ring fused to a five-membered ring. Ex. Adenine and Guanine.
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What is a pyrimidine?
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Nitrogenous base found in nucleotides, characterized by a six-membered ring. Ex. Cytosine, Thymine, and Uracil.
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How does the Watson-Crick model explain Chargaff's rules?
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The model shows that A pairs only with T, and G with C. Shows that in any organism, the amount of A=T and the amount of G=C.
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A forms _ H-bonds with T, and G _ H-bonds with C.
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2; 3.
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What is a gene?
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A unit of inheritance by which an amino acid sequence of a polypeptide is programmed.
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Genes are made of ____, a nucleic acid.
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DNA.
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Two types of nucleic acids are:
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DNA and RNA.
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T or F: DNA provides directions for its own replication.
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True.
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DNA directs synthesis of _____ ____, which controls protein synthesis.
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Messenger RNA (mRNA).
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Protein synthesis occurs in ______.
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Ribosomes.
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mRNA moves into ______ via a nuclear pore to synthesize a protein from a polypeptide and amino acids.
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Cytoplasm.
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Nucleic acids are polymers called _______.
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Polynucleotides.
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Each polynucleotide is made of monomers called _______.
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Nucleotides.
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The portion of a nucleotide without the phosphate group is called a ______.
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Nucleoside (nitrogenous base and sugar).
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A nucleotide is made up of what three components?
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A nitrogenous base, a pentose sugar, and a phosphate group. A.K.A. a nucleoside and a phosphate group.
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In DNA, the sugar is ______; in RNA, the sugar is ribose.
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Deoxyribose (it has a deoxidized OH group-- so where RNA has OH, DNA has H).
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Nucleotide polymers are linked together to build a ______.
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Polynucleotide.
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Adjacent nucleotides are joined by ______ bonds that form between the -OH group on the 3' carbon of one nucleotide and the phosphate on the 5' carbon on the next-- commonl referred to as ______ linkage.
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covalent bonds; phosphodiester linkage.
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T or F: Phosphodiester linkages create a backbone of sugar-phosphate units with nitrogenous bases as appendages.
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True.
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T or F: The sequence of bases along a DNA or mRNA polymer is unique for each gene.
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True.
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A double helix is made up of what components?
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Two polynucleotides spiraling around an imaginary axis.
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T or F: In the DNA double helix, the two backbones run in opposite 5' to 3' directions from each other, an arrangement referred to as antiparallel.
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True.
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T or F: One DNA molecule includes only one gene, if any.
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False. It includes many genes.
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Nitrogenous bases pair up and form _____ bonds with each other.
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Hydrogen bonds: A with T, and G with C.
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_____ _____ store and transmit hereditary information. Examples include: RNA and DNA.
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Nucleic acids.
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What is DNA's function?
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Stores all hereditary information.
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How is RNA's structure different from DNA's?
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RNA's are C, G, A, and U. DNA's are C, G, A, and T. RNA is usually single-stranded, while DNA is double-stranded. DNA's sugar has a deoxydized group of OH so it is just H while RNA has OH.
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What is RNA's function?
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It carries protein-coding instructions from DNA to protein-synthesizing machinery.
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T or F: Cells live forever.
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False. Cells have a limited lifespan.
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T or F: For cell life to continue, cells must divide and produce daughter cells (progeny cells).
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True.
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Through _____, a cell divides to form two identical daughter cells.
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Mitosis.
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What is the molecular basis of inherited cell traits?
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DNA.
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The ______ ________ of nucleotides in DNA are passed from parents to offspring.
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Linear sequences.
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T or F: Two closely related species are more similar in DNA than are more distantly related species.
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True.
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Molecular biology can be used to assess _______ kinship.
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Evolutionary.
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The relationship between structure and function is manifested in the_____ _____ of DNA.
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Double helix.
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Who noted that the specific base pairing suggested a possible copying mechanism for genetic material?
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Watson and Crick.
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Since the two strands of DNA are ________, each strand acts as a template for building a new strand in replication.
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Complimentary.
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In DNA replication, the parent molecule unwinds, and two new daughter strands are built based on what rules?
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Base-pairing rules.
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The _______ DNA molecules consist of one parental strand and one new strand, in DNA replication.
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"Daughter."
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Watson and Crick's ________ model of replication predicts that when a double helix replicates, each daughter molecule will have one old strand (derived from the parent molecule) and one newly made strand.
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Semiconservative model. Most widely recognized model at the time.
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Other models competing at the time of the semiconservative model, were the ______ model (the two parent strands rejoin) and the ______ model (each strand is mix of old and new).
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Conservative; dispersive.
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Whose experiments of labeling the nucleotides of the old strands with a heavy isotope of nitrogen, while any new nucleotides were labeled with a lighter isotope, supported the semiconservative model?
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Matthew Meselson and Franklin Stahl.
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In Meselson and Stahl's experiment, the first replication produced a band of hybrid DNA (eliminating the _____ model), while the second replication produced both light and hybrid DNA (eliminating the _____ model).
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Conservative; dispersive.
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T or F: The copying of DNA is remarkable in its speed and accuracy with very few errors: only 1 per 6 billion nucleotides.
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False: 1 per 10 billion nucleotides.
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More than a dozen ______ and other proteins participate in DNA replication.
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Enzymes.
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Replication begins at special sites called _____ __ ______, where the two DNA strands are separated, opening up a replication "bubble."
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Origins of replication.
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A ______ chromosome is circular and has only 1 origin of replication, while a ______ may have hundreds or thousands.
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Prokaryotic; eukaryotic.
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______ proceeds in both directions from each origin, until the entire molecule is copied.
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Replication.
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At the end of each replication bubble is a ______ _____, a Y-shaped region where new strands are elongating.
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Replication fork.
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______ are enzymes that untwist the double helix at the replication forks.
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Helicases.
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What does a single-strand binding protein do?
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It binds to and stabilizes single-stranded DNA until it can be used as a template.
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_______ corrects "overwinding" ahead of replication forks by breaking, swiveling, and rejoining DNA strands.
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Topoisomerase.
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T or F: DNA polymerase cannot initiate synthesis of a polynucleotide; they can only add nucleotides to the 5' end.
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False: 3' end.
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The initial nucleotide strand is a short RNA _____. It is short (5-10 nucleotides long), and the 3' end serves as the starting point for the new DNA strand -- attached to parent DNA by ______.
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Primer; primase.
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Enzymes called ____ ______ catalyze the elongation of new DNA at a replication fork. Most of them require a primer and a DNA template strand.
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DNA polymerases.
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The rate of elongation is about _____ nucleotides per second in bacteria and 50 per second in human cells.
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500.
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Each nucleotide that is added to a growing DNA strand is a nucleoside _______.
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Triphosphate.
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_____ supplies adenine to DNA and is similar to the ATP of energy metabolism.The difference is in their sugars. ATP has ribose while this one has _________.
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dATP; deoxyribose.
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As each monomer of dATP joins the DNA strand, it loses ____ _____ _____ as a molecule of pyrophosphate.
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Two phosphate groups.
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The _____ structure of the double helix (two strands in opposite directions) affects replication.
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Antiparallel.
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DNA polymerases add nucleotides only to the free ___ end of a growing strand.
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3' end; therefore, a new DNA strand can elongate only in the 5' to 3' direction.
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Daughter strand is ______ to parent strand.
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Anti-parallel.
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Along one template strand of DNA, the DNA polymerase synthesizes a ______ _______ continuously, moving toward the replication fork.
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Leading strand.
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To elongate the other new strand, called the ______ ______, DNA polymerase must work in the direction away from the replication fork.
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Lagging strand.
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The lagging strand is synthesized as a series of segments called ______ ______, which are joined together by ____ ______.
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Okazaki frgments; DNA ligase.
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_____ synthesizes an RNA primer at 5' end of leading strand and of each Okazaki fragment of lagging strand.
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Primase.
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_____ binds to and stabilizes single-stranded DNA until it can be used as a template.
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Single-strand binding protein.
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______ relieves "overwhelming" strain ahead of replication forks by breaking, swiveling, and rejoining DNA strands.
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Topoisomerase.
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___ ____ ___, using parental DNA as a template, it synthesizes new DNA strand by covalently adding nucleotides to the 3' end of a pre-existing DNA strand or RNA primer.
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DNA pol III.
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___ ___ __ removes RNA nucleotides of primer from 5' end and replaces them with DNA molecules.
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DNA pol I.
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____ _____ joins 3' end of DNA that replaces primer to rest of leading strand and joins Okazaki fragments of lagging strand.
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DNA ligase.
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The proteins that participate in DNA replication form a large complex, a "____ _____ _____."
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DNA replication machine.
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The DNA replication machine is probably _____ during the replication process.
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Stationary.
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Recent studies support a model in which DNA polymerase molecules "___ __" parental DNA and "____" newly made daughter DNA molecules.
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Reel in; extrude.
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____ _______ proofread newly made DNA, replacing any incorrect nucleotides.
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DNA polymerases.
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In _____ _____ of DNA, repair enzymes correct errors in base pairing.
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Mismatch repair.
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____ can be damaged by chemicals, radioactive emissions, X-rays, UV light, and certain molecules (in cigarette smoke for example).
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DNA
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In nucleotide excision repair, a ______ cuts out and replaces damaged stretches of DNA.
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Nuclease.
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______ ______ is a disorder caused by an inherited defect in a nucleotide excision repair enzyme. People with this disorder are hypertensive to sunlight.
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Xeroderma pigmentosum.
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Limitations of DNA polymerase create problems for the linear DNA of ______ chromosomes.
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Eukaryotic. The usual replication machinery provides no way to complete the 5' ends, so repeated rounds of replication produce shorter DNA molecules.
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Eukaryotic chromosomal DNA molecules have at their ends nucleotide sequences called _____.
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Telomeres.
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_____ do not prevent the shortening of DNA molecules, but they do postpone the erosion of genes near the ends of DNA molecules.
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Telomeres.
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The shortening of telomeres is most likely connected to _____.
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Aging.
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T or F: If chromosomes of germ cells became longer in every cell cycle, essential genes would eventually be missing from the gametes they produce.
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False: shorter, not longer.
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An enzyme called _____ catalyzes the lengthening of telomeres in germ cells.
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Telomerase.
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The shortening of telomeres might protect cells from cancerous growth by limiting the number of ____ _____.
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Cell divisions.
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T or F: There is evidence of telomerase activity in cancer cells, which may allow cancer cells to disappear.
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False: persist, not disappear.
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A ______ consists of a DNA molecule packed together with proteins.
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Chromosome.
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The _______ chromosome is a double-stranded, circular DNA molecule associated with a ______ amount of protein.
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Bacterial; small.
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Eukaryotic chromosomes have ____ DNA molecules associated with a _____ amount of DNA.
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Linear; large.
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In a bacterium, the DNA is "supercoiled" and found in the region of the cell called the _____.
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Nucleoid.
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______ is a complex of DNA and protein, and is found in the nucleus of eukaryotic cells.
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Chromatin.
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_____ are proteins that are responsible for the first level of DNA packing in chromatin.
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Histones.
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Made up of histones, it looks like "beads on a string."
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Nucleosomes.
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Chromatin is organized into fibers: for the 10 nm fiber, DNA winds around histones to form ______ "beads on a string by linker DNA." For the 30 nm fiber: interactions between ______ cause the thin fiber to coil or fold into this thicker fiber.
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Nucleosomes.
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The 300 nm fiber is formed from 30 nm fiber forms _____ ______ that attach to proteins.
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Looped domains.
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In a ____ chromosome, the looped domains coil further and the width of the chromatid is 700 nm.
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Metaphase.
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Most chromatin is loosely packed in the nucleus during ____ and condenses prior to _____.
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Interphase; mitosis.
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Loosely packed chromatin is called _______.
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Euchromatin.
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During interphase a few regions of chromatin (centromeres and telomeres) are highly condensed into ______.
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Heterochromatin.
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Dense packing of the ______ makes it difficult for the cell to express genetic information coded in these regions.
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Heterochromatin.
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_____ can undergo chemical modifications that result in changes in chromatin organization.
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Histones.
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Phosphorylation of a specific amino acid on a histone tail affects chromosomal behavior during _____.
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Meiosis.
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The information content of DNA is in the form of specific sequences of ______.
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Nucleotides.
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The DNA inherited by an organism leads to specific traits by dictating the synthesis of _____.
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Proteins.
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______ are the links between genotype and phenotype.
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Proteins.
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_____ ______, the process by which DNA directs protein synthesis, includes transcription and translation.
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Gene expression.
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Who first suggested that genes ductate phenotypes through enzymes that catalyze specific chemical reactions.
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Archibald Garrod.
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Linking genes to enzymes required understanding that cells synthesize and degrade molecules in a series of steps, a.k.a a ______ _______.
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Metabolic pathway.
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Who exposed bread mold to x-rays to create mutants that were unable to survive on minimal medium as a result of its inability to synthesize certain molecules.
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George Beadle and Edward Tatum.
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Beadle and Tatum, using crosses, identified three classes of arginine-deficient mutants, each lacking a different _____ necessary for synthesizing argnine.
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Enzyme.
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Beadle and Tatum developed a ________ _________, which states that each gene dictates production of a specific enzyme.
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One gene-one enzyme hypothesis. Since many proteins are composed of several polypeptides, each of which has its own gene, and since some proteins aren't enzymes, researchers renamed it one gene-one polypeptide (protein) hypothesis.
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_____ is the intermediate between genes and the proteins for which they code.
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RNA.
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_____ is the synthesis of RNA under the direction of DNA. It's a specific nucleotide base sequence in DNA gene codes for a specific sequence of nucleotide bases in mRNA.
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Transcription.
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_____ is the synthesis of a polypeptide, which occurs under the direction of mRNA. It's the specific sequence of nucleotide bases in mRNA codes for synthesis of a specific sequence of amino acids in a particular protein (primary structure).
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Translation.
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_____ are the sites of translation.
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Ribosomes.
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Transcription occurs in the _____ region.
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Nucleoid.
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mRNA produced by transcription is immediately translated without more processing in _______.
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Prokaryotes.
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In a eukaryotic cell, the ____ ______ separates transcription from translation.
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Nuclear envelope.
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Eukaryotic RNA transcripts are modified through _____ _______ to yield finished mRNA.
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RNA processing.
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A ____ _____ is the initial RNA transcript from any gene.
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Primary transcript.
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The central dogma is the concept that cells are governed by what cellular chain of command?
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DNA to RNA to protein.
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RNA synthesis is catalyzed by ___ ______, which pries the DNA strands apart and hooks together the RNA nucleotides.
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RNA polymerase.
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RNA synthesis follows the same base-pairing rules as DNA, except ____ substitutes for Thymine.
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Uracil.
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The DNA sequence where RNA polymerase attaches is called the ______.
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Promoter.
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In bacteria, the sequence signaling the end of transcription is called the ______.
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Terminator.
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The stretch of DNA that is transcribed is called a ______ ____.
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Transcription unit.
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What are the three stages of RNA transcription?
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Initiation, elongation, and termination.
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Initiation of transcription in prokaryotes occurs in the _____ ____. The binding of the enzyme _____ ______ to promoter region of DNA spreads apart DNA strands,
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Nucleoid region; RNA polymerase.
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During elongation of the RNA strand, RNA polymerase moves along one strand of DNA while mRNA assembles by adding nucleotide to the ___ end of elongating mRNA molecule. mRNA elongates in what direction?
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3' end; 5' to 3'.
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During elongation of transcription, the base sequence in the DNA strand moved along the template strand determines the base sequence in the mRNA due to which base pairing rules?
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C with G, (DNA) T with (mRNA) A, and (DNA) A with (mRNA) U in the 5' to 3' direction.
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In elongation of transcription, nucleotides added are initially triphosphated--2PO4 cleaved off to give energy for what?
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Bond formation.
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In termination of transcription in bacteria, the polymerase stops transcription at the end of the _____ _____. When the RNA polymerase reaches the terminator, what three things occur?
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Terminator region. mRNA molecule is complete, RNA polymerase falls off the DNA template, and DNA becomes a helix again.
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mRNA, RNA polymerase, and DNA.
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In eukaryotic cells, transcription occurs in the ____. Binding of RNA polymerase II to the promoter is regulated by ____ _____ factors.
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Nucleus; protein transcription factors.
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What do protein transcription factors do?
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Factors usually enhance RNA polymerase binding to increase the rate of transcription. They control which genes are expressed at any time.
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Termination of the transcript in eukaryotic cells involves a ______ signal.
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Polyadenylation signal (AAUAAA).
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Initial product of transcription is "______" which is modified in the nucleus before the genetic messages are dispatched to the cytoplasm.
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"pre-mRNA."
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Each end of a pre-mRNA molecule is modified in a certain way: the 5' end receives a modified nucleotide ___ ____, while the 3' end gets a _____ ____.
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5' cap; poly A-tail.
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The modifications of the pre-mRNA molecule share what functions?
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They seem to facilitate the export of mRNA, they protect mRNA from hydrolytic enzymes, and they help ribosomes attach to the 5' end.
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Facilitate, protect, and help.
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Most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides, called intervening sequences, or ______, that lie between coding regions.
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Introns.
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Other regions of stretches of nucleotides are called ____ because they are eventually expressed and usually translated into amino acids.
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Exons.
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____ _______ removes introns and joins exons, creating an mRNA molecule with a continuous coding sequence.
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RNA splicing.
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______ consist of a variety of proteins and several small nuclear ribonucleoproteins (snRNPs) that recognize the splice sites. They sometimes carry out RNA splicing.
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Spliceosomes.
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_______ are catalytic RNA molecules that function as enzymes and can splice RNA. Rendered obsolete the belief that all biological catalysts were proteins.
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Ribozymes.
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What three properties of RNA enable it to function as an enzyme?
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It can form a 3-d structure because of its ability to base pair with itself; some bases in RNA contain functional groups; RNA may hydrogen-bond with other nucleic acid molecules.
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3-d, functional groups, hydrogen bond.
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Some genes can encode more than one kind of polypeptide, depending on which segments are treated as ____ during RNA splicing. These variations are called _____ _____ _____.
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Exons; alternative RNA splicing.
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Proteins often have a modular architecture consisting of discrete regions called ______.
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Domains.
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In many cases, different exons code for the different _____ in a protein.
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Domains.
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_____ ______ may result in the evolution of new proteins, which allows for crossing over between exons of alleles (prevents interrupting coding sequences during cross-over events).
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Exon shuffling.
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