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177 Cards in this Set

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