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123 Cards in this Set
- Front
- Back
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What is the definition of genetics?
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Genetics is the study of inheritance and inheritable traits as expressed in an organism’s genetic material. Geneticists study many aspects of inheritance, including the physical structure and function of genetic material, mutations, and the transfer of genetic material among organisms.
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Compare and contrast the genomes of prokaryotes and eukaryotes.
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TBA
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What is the def. of a genome of a cell or virus?
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The genome of a cell or virus is its entire genetic complement, including both its genes—specific sequences of nucleotides that code for polypeptides or RNA molecules—and nucleotide sequences that connect genes to one another.
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What are the genomes of cells and DNA viruses composed solely of?
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The genomes of cells and DNA viruses are composed solely of molecules of deoxyribonucleic acid (DNA), whereas RNA viruses use ribonucleic acid instead
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Describe the structure of DNA, and discuss how it facilitates the ability of DNA to act as genetic material
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TBA
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What are nucleic acids, and what are they polymers of, and what is the molecular make-up of nucleic acids?
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nucleic acids are polymers of nucleotides, each of which contains a pentose sugar (deoxyribose in DNA, ribose in RNA), a phosphate, and one of five nitrogenous bases (guanine, cytosine, adenine, thymine, or uracil).
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What are the five nitrogenous bases ?
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The five nitrogenous bases are(guanine, cytosine, adenine, thymine, and uracil.
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What are base pairs (bp)
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The five nitrogenous bases hydrogen-bond in specific ways called base pairs (bp):
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What are the 2 base pairs (bp) of DNA? How many hydrogen bonds are involved?
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In DNA, the complementary bases guanine and cytosine bond to one another with three hydrogen bonds, and the complementary bases adenine and thymine bond to one another with two hydrogen bonds.
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What is the base pair (bp) of RNA?
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In RNA, uracil (not thymine) bonds with adenine
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What are the pentose sugars in DNA? in RNA?
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The pentose sugar in DNA is deoxyribose.
in ribose it is RNA. |
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What is the def of genetics?
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Genetics – study of inheritance and inheritable traits as expressed in an organism’s genetic material
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What is the def of a genome?
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Genome – the entire genetic complement of an organism
Includes its genes and nucleotide sequences |
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What structures do DNA nucleotides and RNA nucleotides have in common?
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Base pairing between the complementary bases guanine (G) and cytosine (C) formed by three hydrogen bonds, found in both DNA and RNA.
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What holds the double-stranded antiparallel strands of nucleotides to one another in DNA?
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Double-stranded DNA, which consists of antiparallel strands of nucleotides
held to one another by the hydrogen bonding between complementary bases |
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What 2 bases have structural similarities?
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Notice the structural similarities between thymine and uracil.
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What 2 molecules link Deoxyribonucleotides to form the two backbones of a helical, double-stranded DNA (dsDNA) molecule?
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Deoxyribonucleotides are linked through their sugars and phosphates to form the two backbones of a helical, double-stranded DNA (dsDNA) molecule
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What atoms of deoxyribose are numbered 1′ through 5′ ?.
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The carbon atoms of deoxyribose are numbered 1′ (pronounced “one prime”) through 5′.
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Why is one end of a DNA strand called the 5′ end ?
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One end of a DNA strand is called the 5′ end because it terminates in a phosphate group attached to a 5′ carbon; the opposite (3′) end terminates with a hydroxyl group bound to a 3′ carbon of deoxyribose.
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What do scientists mean when they say the two strands are antiparallel?
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Scientists say the two strands are antiparallel because The two strands are oriented in opposite directions to each other; one strand runs in a 3′ to 5′ direction, while the other runs in a 5′ to 3′ direction.
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Since the lengths of DNA molecules are not usually given in metric units, what is the length measured in?
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The lengths of DNA molecules are not usually given in metric units; instead the length of a DNA molecule is expressed in base pairs (bp). For example, the genome of Carsonella ruddii is 160,000 bp long, making it the smallest known cellular genome.
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In what 2 ways does the structure of DNA help explain its ability to act as genetic material?
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1st- the linear sequence of nucleotides carries the instructions for the synthesis of polypeptides and RNA molecules—2nd, the complementary structure of the two strands allows a cell to make exact copies to pass to its progeny.
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The chromosome of Mycobacterium tuberculosis is 4,411,529 bp long. A scientist who isolates and counts the number of nucleotides in its DNA molecule discovers that there are 2,893,963 molecules of guanine. How many molecules of the other three nucleotides are in the original DNA?
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TBA
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How many base pairs does the human genome have? in ? many nuclear DNA molecules and a mitochondrial DNA molecule?
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The human genome has about 3 billion base pairs in 46 nuclear DNA molecules and a mitochondrial DNA molecule,
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How many meters long is the human genome? in µm?
if all 47 molecules from a single cell were laid end to end? |
and it would be 1.6 meters or 5'3" or (1,600,000 µm) long if all 47 molecules from a single cell were laid end to end.
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Where is the human cellular genome packed into? It is typically only ? µm in diameter.
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Most of a human cellular genome is packed into a nucleus that is typically only 5 µm in diameter.
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The DNA of prokaryotic genomes is found in what two structures?
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The DNA of prokaryotic genomes is found in two structures: chromosomes and plasmids.
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Prokaryotic cells package the main portion of their DNA, along with associated molecules of protein and RNA, as one or two distinct ?what? .
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Prokaryotic cells package the main portion of their DNA, along with associated molecules of protein and RNA, as one or two distinct chromosomes.
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Prokaryotic cells have a single copy of each chromosome and are called ?
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Prokaryotic cells have a single copy of each chromosome and are called haploid cells.
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A typical prokaryotic chromosome consists of a circular molecule of DNA localized in a region of the cytoplasm called the ?.
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A typical prokaryotic chromosome consists of a circular molecule of DNA localized in a region of the cytoplasm called the nucleoid.
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Is there a membrane that surrounds a nucleoid of a prokaryote? ,
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With few exceptions, no membrane surrounds a nucleoid, though the chromosome is packed in such a way that a distinct boundary is visible between the nucleoid and the rest of the cytosol.
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Prokaryote Chromosomal DNA is held in place by what 2 types of molecules?
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Prokaryote Chromosomal DNA is folded into loops that are 50,000–100,000 bp long held in place by molecules of protein and RNA
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What is Archaeal DNA wrapped around?
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Archaeal DNA is wrapped around globular proteins called histones.
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What enzyme further folds and supercoils the entire prokaryotic chromosome like a skein of yarn into a compact mass?
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The enzyme gyrase further folds and supercoils the entire prokaryotic chromosome like a skein of yarn into a compact mass.
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Are bacterial chromosomes surrounded by a membrane? What are they packaged in?
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Bacterial chromosomes are packaged in a region of the cytosol called the nucleoid, which is not surrounded by a membrane.
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What are plasmids in prokaryotic cells ?
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In addition to chromosomes, many prokaryotic cells contain one or more plasmids, which are small molecules of DNA that replicate independently of the chromosome.
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Describe the shape and size of plasmids.
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Plasmids are usually circular and 1–5% of the size of a prokaryotic chromosome ranging in size from a few thousand bp to a few million bp.
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Describe the function of plasmids prokaryotic chromosome
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Each plasmid carries information required for its own replication, and often for one or more cellular traits. Typically, genes carried on plasmids are not essential for normal metabolism, for growth, or for cellular reproduction but can confer advantages to the cells that carry them.
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Researchers have identified many types of plasmids - what are they sometimes also called?
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Researchers have identified many types of plasmids (sometimes also called factors),
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Name 5 types of plasmids
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Many types of plasmids:
-Fertility factors -Resistance factors -Bacteriocin factors -Virulence plasmids – ie capsule -Cryptic plasmids |
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in regards to the structure of Eukaryotic Genomes, Eukaryotic genomes consist of both ?what? and ?what?
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The Structure of Eukaryotic Genomes
Eukaryotic genomes consist of both nuclear and extranuclear DNA. |
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How many nuclear chromosomes do eukaryotic cells have in their genomes?
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eukaryotic cells have more than one nuclear chromosome in their genomes, though one species of Australian ant has a single chromosome per nucleus, and some eukaryotic cells such as mammalian red blood cells lose their chromosomes as they mature.
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What is the def on diploid?
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Eukaryotic cells are often diploid; that is, they have two copies of each chromosome.
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How are eukaryotic chromosomes different from their typical prokaryotic counterparts?
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Eukaryotic chromosomes differ from their typical prokaryotic counterparts in that they are sequestered within a nucleus and are linear (rather than circular).
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What 2 things together are called the nuclear envelope?
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the nucleus is an organelle surrounded by two membranes, which together are called the nuclear envelope.
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What are the structures involved in the packaging of eukaryotic chromosomes?
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The structures involved in the packaging of eukaryotic chromosomes are: DNA and globular eukaryotic histones, . nucleosomes, chromatin fibers, when active are packed to form euchromatin or inactive they form heterochromatin
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Describe 4 stages of eukaryotic nuclear chromosomal packaging.
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(a) Histones stabilize and package DNA to form nucleosomes connected by linker DNA. (b) Nucleosomes clump to form chromatin fibers. (c) Chromatin fibers fold and are organized into active euchromatin and inactive heterochromatin. (d) During nuclear division (mitosis), duplicated chromatin fully condenses into a mitotic chromosome that is visible by light microscopy.
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What happens to chromosomes just prior to mitosis, a
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Prior to mitosis, a cell replicates its chromosomes and then condenses them into pairs of chromosomes visible by light microscopy ( One molecule of each pair is destined for each daughter nucleus. The net result is that each DNA molecule is packaged as a mitotic chromosome that is 50,000 × shorter than its extended length.
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Are all of the DNA of a eukaryotic genome contained in its nuclear chromosomes?
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Not all of the DNA of a eukaryotic genome is contained in its nuclear chromosomes; most eukaryotic cells also have mitochondria, and plant, algal, and some protozoan cells have chloroplasts that also contain DNA.
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Compare and contrast the genomes of prokaryotes and eukaryotes
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# of chromosomes
Plasmids present? type of nucleic acid location of DNA Histones present |
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Compare and contrast the genomes of prokaryotes and eukaryotes
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In summary, the haploid genome of a prokaryotic cell consists of both chromosomal DNA, which is usually in a single circular chromosome, and all extrachromosomal DNA in the form of plasmids that are present. In contrast, a eukaryotic genome consists of nuclear chromosomal DNA in one or more linear chromosomes, plus all the extranuclear DNA in mitochondria, chloroplasts, and any plasmids that are present.
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Describe the replication of DNA as a semiconservative process.
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TBA
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Compare and contrast the synthesis of leading and lagging strands in DNA replication
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TBA
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What is the polymerization processes?
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DNA replication is an anabolic polymerization process that allows a cell to pass copies of its genome to its descendants. Though bacterial, archaeal, and eukaryotic cells package DNA differently, all three types employ similar mechanisms for DNA replication.
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what do all polymerization processes require?
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all polymerization processes require monomers (building blocks) and energy.
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what are Triphosphate deoxyribonucleotides?
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Triphosphate deoxyribonucleotides—DNA nucleotides with three phosphate groups linked together by two high-energy bonds—serve both functions in DNA replication.
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where do the building blocks of DNA get the energy required for DNA synthesis?
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the building blocks of DNA carry within themselves the energy required for DNA synthesis
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How does the structure of guanosine triphosphate nucleotide (dGTP), differ from that of cytidine triphosphate (dCTP), thymidine triphosphate (dTTP), and adenosine triphosphate (dATP)
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The structure of guanosine triphosphate nucleotide (dGTP), shown in Figure 7.4a, differs from that of cytidine triphosphate (dCTP), thymidine triphosphate (dTTP), and adenosine triphosphate (dATP) only in the kind of base present.
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How does the structure of dATP differ from that of the energy-storage molecule ATP?
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dATP has a structure similar to that of the energy-storage molecule ATP, except that ATP is a ribonucleotide rather than a deoxyribonucleotide
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Why do Biologists say that DNA replication is semiconservative?
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Biologists say that DNA replication is semiconservative because each daughter DNA molecule is composed of one original strand and one new strand.
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What is the key to DNA replication
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The key to DNA replication is the complementary structure of the two strands: Adenine and guanine in one strand bond with thymine and cytosine, respectively, in the other. DNA replication is a simple concept—a cell separates the two original strands and uses each as a template for the synthesis of a new complementary strand.
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What are the two strands and what do they bond with
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Adenine and guanine in one strand bond with thymine and cytosine, respectively, in the other.
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What is the concept of DNA replication?
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DNA replication is a simple concept—a cell separates the two original strands and uses each as a template for the synthesis of a new complementary strand.
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What does the term "the origin" mean in DNA replication?
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DNA replication begins at a specific sequence of nucleotides called an origin
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What is a replication fork?
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a replication fork is ?
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Describe the Initial processes in DNA replication
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The cell removes proteins (histones in eukaryotes and archaea) from the DNA molecule. Helicase unzips the double helix—breaking hydrogen bonds between complementary base pairs—to form a replication fork.
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Why is DNA replication termed “semiconservative”?
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TBA
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What does the enzyme called DNA polymerase III do?
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enzyme called DNA polymerase III binds to each strand. Scientists have identified five kinds of prokaryotic DNA polymerase, and six kinds from eukaryotes. These eleven enzymes vary in their specific functions, but all of them share one important feature—they synthesize
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Scientists have identified five kinds of prokaryotic DNA polymerase, and six kinds from eukaryotes. what is the one important feature they share?
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Scientists have identified five kinds of prokaryotic DNA polymerase, and six kinds from eukaryotes. These eleven enzymes vary in their specific functions, but all of them share one important feature—they synthesize DNA by adding nucleotides only to a hydroxyl group at the 3′ end of a nucleic acid
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what are the names of the 2 new strands cells synthesize in two different ways?
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One new strand, called the leading strand, is synthesized continuously as a single long chain of nucleotides. The other new strand, called the lagging strand, is synthesized in short segments that are later joined.
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What is the 1st step in DNA replication?
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DNA replication begins at the origin. First, a cell removes chromosomal proteins, exposing the DNA helix.
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What is the 2nd step in DNA replication?
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DNA replication 2nd step: Next, an enzyme called DNA helicase locally “unzips” the DNA molecule by breaking the hydrogen bonds between complementary nucleotide bases, which exposes the bases in a replication fork Other protein molecules stabilize the single strands so that they do not rejoin while replication proceeds.
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What is the 3rd step in DNA replication?
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Continuous synthesis of the leading strand. DNA synthesis always moves in the 5′ to 3′ direction, so the leading strand is synthesized toward the replication fork.
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What is the 4thstep in DNA replication?
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Discontinuous synthesis of the lagging strand, which proceeds moving away from the replication fork.
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Why is DNA replication termed “semiconservative”?
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“Semiconservative” refers to the fact that each of the daughter molecules retains one parental strand and has one new strand; in other words, each is half new and half old.
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What are Okazaki fragments?
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Actual Okazaki fragments are about 1000 nucleotides long.
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DNA polymerases replicate DNA in which direction? 5 to 3 or 3 to 5?
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DNA polymerases replicate DNA in only one direction—5′ to 3′—like a jeweler stringing pearls to make a necklace, adding them one at a time, always moving from one end of the string to the other.
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Is the leading strand synthesized continuously as a single long chain of nucleotidesor synthesized in short segments that are later joined?
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the leading strand, is synthesized continuously as a single long chain of nucleotides. The other new strand, called the lagging strand, is synthesized in short segments that are later joined.
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What is the 1st of 5 steps that a cell does when synthesizing a leading strand?
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An enzyme called primase synthesizes a short RNA molecule that is complementary to the template DNA strand. This RNA primer provides the 3′ hydroxyl group required by DNA polymerase.
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What is the 2nd of 5 steps that a cell does when synthesizing a leading strand?
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Triphosphate deoxyribonucleotides form hydrogen bonds with their complements in the parental strand. Adenine nucleotides bind to thymine nucleotides, and guanine nucleotides bind to cytosine nucleotides.
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What is the 3rd of 5 steps that a cell does when synthesizing a leading strand?
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Using the energy in the high-energy bonds of the triphosphate deoxyribonucleotides, DNA polymerase III covalently joins them one at a time by dehydration synthesis to the leading strand. DNA polymerase III can add about 500–1000 nucleotides per second to a new strand.
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What is the 4th of 5 steps that a cell does when synthesizing a leading strand?
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DNA polymerase III also performs a proofreading function (not shown). About one out of every 100,000 nucleotides is mismatched with its template; for instance, a guanine might become incorrectly paired with a thymine. DNA polymerase III recognizes most such errors and removes the incorrect nucleotides before proceeding with synthesis. This role, known as the proofreading exonuclease function, acts like the delete key on a keyboard, removing the most recent error. Because of this proofreading exonuclease function, only about one error remains for every 10 billion (1010) base pairs replicated.
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What is the 5th of 5 steps that a cell does when synthesizing a leading strand?
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Another DNA polymerase—DNA polymerase I—replaces the RNA primer with DNA (not shown). Note that researchers named DNA polymerase enzymes in the order of their discovery, not the order of their actions.
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Why does the 5′ end of an existing nucleic acid move away from the replication fork as it synthesizes a lagging strand?
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Because DNA polymerase III adds nucleotides only to the 5′ end of an existing nucleic acid, it moves away from the replication fork as it synthesizes a lagging strand
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What is the 1st of 5 steps in the synthesis of a lagging strand?
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As with the leading strand, primase synthesizes RNA primers.
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What is the 2nd of 5 steps in the synthesis of a lagging strand?
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Nucleotides pair up with their complements in the template—adenine with thymine, and cytosine with guanine.
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What is the 3rd of 5 steps in the synthesis of a lagging strand?
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DNA polymerase III joins neighboring nucleotides and proofreads. In contrast to synthesis of the leading strand, however, the lagging strand is synthesized in discontinuous segments called Okazaki fragments, named for the Japanese scientist Reiji Okazaki (1930–1975), who first identified them. Each Okazaki fragment requires a new RNA primer and consists of 1000 to 2000 nucleotides.
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What is the 4th of 5 steps in the synthesis of a lagging strand?
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DNA polymerase I replaces the RNA primers of Okazaki fragments with DNA and further proofreads the daughter strand.
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What is the 5th of 5 steps in the synthesis of a lagging strand?
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DNA ligase seals the gaps between adjacent Okazaki fragments to form a continuous DNA strand.
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Does the synthesis of the leading strand proceed ontinuously or discontinuously?
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The synthesis of the leading strand proceeds continuously toward the replication fork from a single RNA primer at the origin, following helicase and the replication fork down the DNA. The lagging strand is synthesized away from the replication fork, discontinuously as a series of Okazaki fragments, each of which begins with its own RNA primer. All the primers are eventually replaced with DNA nucleotides, and ligase joins the Okazaki fragments.
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What is an RNA primer? What replaces all the primers in DNA replication?
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A primer is a strand of nucleic acid that serves as a starting point for DNA replication. They are required because the enzymes that catalyze replication, DNA polymerases, can only add new nucleotides to an existing strand of DNA. All the primers are eventually replaced with DNA nucleotides, and ligase joins the Okazaki fragments.
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What are connector proteins?
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The 2 DNA polymerases responsible for replicating the leading and lagging strands are linked together with connector proteins.
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What does DNA helicase do?
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An enzyme that catalyzes the unwinding of the DNA helix
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What is primase?
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An enzyme that creates an RNA primer for initiation of DNA replication.
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What does DNA polymerase do?
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It is an enzyme that catalyses the synthesis of DNA.
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What does DNA ligase do?
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DNA ligase joins DNA fragments
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What does RNAse do?
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RNA-splitting enzyme: an enzyme that splits or degrades RNA.
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How many RNA primers are needed to start the leading strand synthesis process? How many required for the lagging?
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only one RNA primers is needed to start the process.
Each Okasaki fragment requires it's own RNA primer. |
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What is different in DNA replication in bacteria?
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DNA replication is bidirectional; that is, DNA synthesis proceeds in both directions from the origin. In bacteria, the process of replication proceeds from a single origin, so it involves two sets of enzymes, two replication forks, two leading strands, and two lagging strands
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How many origins to bacterial chromosomes have? Eukaryotic chromosomes?
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Bacterial chromosomes have a single origin, but eukaryotic chromosomes have thousands of origins.
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What does helicase do?
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The unzipping and unwinding action of helicase introduces supercoils into the DNA molecule ahead of the replication forks.
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What does the enzyme topoisomerase do?
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The enzyme topoisomerase removes these supercoils by cutting the DNA, rotating the cut ends in the direction opposite the supercoiling, and then rejoining the cut ends.
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What is methylation?
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Bacterial DNA replication is further complicated by methylation of the daughter strands, in which a cell adds a methyl group (—CH3) to one or two bases that are part of specific nucleotide sequences. Bacteria typically methylate adenine bases and only rarely a cytosine base.
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What role does Methylation in a variety of cellular processes?
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Methylation plays a role in a variety of cellular processes, including the following:
• Control of genetic expression. In some cases, genes that are methylated are “turned off” and are not transcribed, whereas in other cases methylated genes are “turned on” and are transcribed. • Initiation of DNA replication. In many bacteria, methylated nucleotide sequences play a role in initiating DNA replication. • Protection against viral infection. Methylation at specific sites in a nucleotide sequence enables cells to distinguish their DNA from viral DNA, which lacks methylation. The cells can then selectively degrade the viral DNA. • Repair of DNA. The role of methylation in some DNA repair mechanisms is discussed . |
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In what ways does eukaryotic replication differ from prokaryotic replication ?
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Eukaryotic replication differs from prokaryotic replication in some significant ways:
• Eukaryotic cells use four different DNA polymerases to replicate DNA. DNA polymerase α initiates replication, including synthesis of a primer—the function performed by primase in bacteria. DNA polymerase δ elongates the leading strand, and DNA polymerase ε appears to be responsible for replicating the lagging strand. DNA polymerase γ replicates mitochondrial DNA. • The large size of eukaryotic chromosomes necessitates thousands of origins per molecule, each generating two replication forks; otherwise, the replication of eukaryotic genomes would take days instead of hours. • Eukaryotic Okazaki fragments are shorter than those of bacteria—100 to 400 nucleotides long. • Plant and animal cells methylate cytosine bases exclusively. |
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What is the relationship between an organism’s genotype and its phenotype?
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Tall the physical parts, the molecules, macromolecules, cells and other structures, are built and maintained by cells following the instructions give by the genotype.
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What is the definition of a genotype?
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The genotype of an organism is the actual set of genes in its genome. A genotype differs from a genome in that a genome also includes nucleotides that are not part of genes, such as the nucleotide sequences that link genes together. At the molecular level, the genotype consists of all the series of DNA nucleotides that carry instructions for an organism’s life
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What is the definition of a phenotype?
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Phenotype refers to the physical features and functional traits of an organism, including characteristics such as structures, morphology, and metabolism. For example, the shape of a cell, the presence and location of flagella, the enzymes and cytochromes of electron transport chains, and membrane receptors that trigger chemotaxis are all phenotypic traits
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What is the central dogma of genetics?
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Transcription of DNA to RNA to protein
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Define process called transcription.
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Cells do not transfer the information coded in DNA directly but first make an RNA copy of the gene. In this copying process, called transcription, 5 the information is copied as RNA nucleotide sequences
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What is the central dogma of genetics?
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The central dogma of genetics. A cell transcribes RNA from a DNA gene and then translates polypeptides using the code carried by the RNA molecules. Polypeptides determine phenotype by acting as structural, enzymatic, and regulatory proteins.
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What happens to transcribe and translate the genotype so it can be expressed as a phenotype.
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To a ribosome, DNA is like a foreign language written in a foreign alphabet. Thus, a cell must first transcribe the “foreign alphabet” of DNA nucleotides (genes) into the more “familiar alphabet” of RNA nucleotides; then it must translate the message formed by these “letters” into the “words” (amino acids) that make up the “message” (a polypeptide). In this way a genotype can be expressed as a phenotype.
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What does a ribosome do?
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Ribosomes are located in the cytoplasm of a cell and is composed of RNA and protein and is the site of protein synthesis. Ribosomes exist in both eukaryotic and prokaryotic cells.
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Describe three steps in RNA transcription, mentioning the following: DNA, RNA polymerase, promoter, 5′ to 3′ direction, and terminator.
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TBA
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What are the 3 main types of RNA that cells transcribe from DNA?
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RNA primer molecules - for DNA polymerase to use during DNA replication
• messenger RNA (mRNA) molecules - carry genetic information from chromosomes to ribosomes • ribosomal RNA (rRNA) molecules, - which combine with ribosomal polypeptides to form ribosomes—the organelles that synthesize polypeptides • transfer RNA (tRNA) molecules- which deliver amino acids to ribosomes |
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Where does transcription occur?
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Transcription occurs in the nucleoid region of the cytoplasm in bacteria.
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What are the steps of RNA transcription?
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The steps of RNA transcription are: initiation of transcription, elongation of the RNA transcript, and termination of transcription
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What is the difference between a promoter sequence and an origin?
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A promoter is a DNA sequence that initiates transcription; an origin is a point where DNA replication begins.
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What are the 3 events in the transcription of RNA in prokaryotes?
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(1) Initiation of transcription. (2) Elongation of the RNA transcript.
(3) Termination of transcription, which is effected by the release of RNA polymerase. |
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What does RNA polymerase do?
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RNA polymerases—the enzymes that synthesize RNA
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What is a promoter and what does it do?
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RNA polymerases—the enzymes that synthesize RNA—bind to specific nucleotide sequences called promoters, each of which is located near the beginning of a gene and initiates transcription
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What is a nu·cle·o·tide?
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structural unit of nucleic acids, also called bases. they join together to form the famous DNA double helix.
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What are the steps in Initiation of Transcription?
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1 - In bacteria, a polypeptide subunit of RNA polymerase called the sigma factor is necessary for recognition of a promoter. Once it adheres to a promoter sequence, RNA polymerase unwinds and unzips the DNA molecule in the promoter region and then travels along the DNA, unzipping the double helix as it moves . One type of RNA polymerase transcribes RNA primer, and a second type of RNA polymerase transcribes mRNA, rRNA, and tRNA.
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