The nitrogen-containing bases in nucleic acids are derivatives of _____.
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Adenine
Guanine
The purine bases with double rings are what?
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Cytosine
Thymine
The pyrimidine bases with double rings are what?
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uracil
RNA contains the same pyrimidine and purine bases as DNA, except thymine (T) is replaced by _____.
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Ribose
The five-carbon sugar in RNA which gives the letter R in the abbreviation of RNA.
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Deoxyribose
The five-carbon sugar in DNA, is similar to ribose except that there is no hydroxyl group.
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Nucleosides
A combination of sugar and a base, is produced when the nitrogen atom in a pyrimidine or a purine base forms an N-glycosidic bond to carbon 1 of a sugar, either ribose or deoxyribose.
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Nucleotides
These are nucleosides in which a phosphate group bonds to the —OH group on carbon 5 of ribose or deoxyribose.
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Nucleic Acids
These are polymers of many nucleotides in which the 3′-hydroxyl group of the sugar in one nucleotide bonds to the phosphate group on the 5′-carbon atom in the sugar of the next nucleotide.
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Phosphodiester bond
The link between the sugars in adjacent nucleotides.
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Primary Structure of Nucleic Acid
It is this sequence of bases that carries the genetic information from one cell to the next.
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double helix
In 1953, *James Watson* and *Francis Crick* proposed that DNA was a ______ that consisted of two polynucleotide strands winding about each other like a spiral staircase.
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James Watson and Francis Crick
In 1953, *they* proposed that DNA was a double helix that consisted of two polynucleotide strands winding about each other like a spiral staircase.
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Complementary Base Pairs
The pairs AT and GC; are the specific pairing of the bases occurs because adenine and thymine form only two hydrogen bonds, while cytosine and guanine form three hydrogen bonds.
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DNA Replication
This process begins when helicase catalyzes the unwinding of a portion of the double helix by breaking the hydrogen bonds between the complementary bases.
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RNA
It makes up most of the nucleic acid found in the cell, is involved with transmitting the genetic information needed to operate the cell.
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Ribosomal RNA (rRNA)
* The most abundant type of RNA is combined with proteins to form ribosomes. * Ribosomes, which are the sites for protein synthesis, consist of two subunits: a large subunit and a small subunit.
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Messenger RNA (mRNA)
It carries genetic information from the DNA, located in the nucleus of the cell, to the ribosomes located in the cytoplasm.
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Transfer RNA (tRNA)
The smallest of the RNA molecules interprets the genetic information in mRNA and brings specific amino acids to the ribosome for protein synthesis.
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Anticodon
A series of three bases that complements three bases on mRNA.
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Transcription
Genetic information for the synthesis of a protein is copied from a gene in DNA to make mRNA.
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Translation
tRNA molecules convert the information in the mRNA into amino acids, which are placed in the proper sequence to synthesize a protein.
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Genetic Code
It consists of a series of three nucleotides in mRNA called codons that specify the amino acids and their sequence in the protein.
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Protein Synthesis
* Once the mRNA is synthesized, it migrates out of the nucleus into the cytoplasm to the ribosomes. * In the translation process, tRNA molecules, amino acids, and enzymes convert the codons on mRNA to build a protein.
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Activation
_____ of tRNA occurs when aminoacyl–tRNA synthetase forms an ester bond between the carboxylate group of its amino acid and the hydroxyl group on the acceptor stem.
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Translocation
The initial tRNA detaches from the ribosome, which shifts to the next available codon.
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start codon
The first codon in mRNA is a ________, AUG, which forms hydrogen bonds with methionine–tRNA.
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methionine
Another tRNA hydrogen bonds to the next codon, placing a second amino acid adjacent to ______.
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peptide
A ____ bond forms between the C-terminal of methionine and the N-terminal of the second amino acid
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chain elongation,
During _______. the ribosome moves along the mRNA from codon to codon, so that the tRNAs can attach new amino acids to the growing protein chain.
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polysome
Sometimes, ______ translates the same strand of mRNA to produce several copies of the protein at the same time.
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Stop codons
____ are encountered which the termination of protein synthesis and the release of the protein chain from the ribosome.
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Mutation
A change in the nucleotide sequence of DNA.
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somatic cell
If a mutation occurs in a ______, the altered DNA will be limited to that cell and its daughter cells.
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cancer
If the mutation causes uncontrolled growth, _____ could result.
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germ cell
If a mutation occurs in a ____, then all the DNA produced in a new individual will contain the same genetic change.
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genetic disease
When a mutation severely alters the function of structural proteins or enzymes, the new cells may not survive or the person may exhibit a _____.
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Point Mutation
The replacement of one base in the template strand of DNA with another.
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Silent Mutation
This occurs if a substitution gives a codon for the same amino acid, and there is no change in the amino acid sequence in the protein.
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Frameshift Mutation
A base is inserted into or deleted from the normal order of bases in the template strand of DNA.
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Genetic Disease
It is the result of a defective enzyme caused by a mutation in its genetic code.
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Galactosemia
The transferase enzyme required for the metabolism of galactose-1-phosphate is absent, resulting in the accumulation of galactose-1-phosphate, which leads to cataracts and mental retardation.
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Cystic fibrosis
* It is caused by a mutation in the gene for the protein that regulates the production of stomach fluids and mucus * It is one of the most common inherited diseases in children, in which thick mucus secretions make breathing difficult and block pancreatic function.
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Down syndrome
It is the leading cause of mental retardation, occurring in about 1 of every 800 live births; the mother’s age strongly influences its occurrence.
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Familial hypercholesterolemia
It occurs when there is a mutation of a gene on chromosome 19, which produces high cholesterol levels that lead to early coronary heart disease in people 30 to 40 years old
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Muscular dystrophy
* It is caused by a mutation in the X chromosome. * This muscle-destroying disease appears at about age 5, with death by age 20, and occurs in about 1 of 10 000 males.
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Huntington’s disease
* It affects the nervous system, leading to total physical impairment. * It is the result of a mutation in a gene on chromosome 4, which can now be mapped to test people in families with a history of HD.
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Sickle-cell anemia
* It is caused by a defective form of hemoglobin resulting from a mutation in a gene on chromosome 11. * It decreases the oxygen-carrying ability of red blood cells, which take on a sickled shape, causing anemia and plugged capillaries from red blood cell aggregation.
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Hemophilia
* It is the result of one or more defective blood-clotting factors that lead to poor coagulation, excessive bleeding, and internal hemorrhages.
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Tay–Sachs disease
* It is the result of defective hexosaminidase A, which causes an accumulation of gangliosides and leads to mental retardation, loss of motor control, and early death.
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Viruses
* These are small particles of 3 to 200 genes that cannot replicate without a host cell * It does not have the necessary material such as nucleotides and enzymes to make proteins and grow.
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Viral Infection
* It begins when an enzyme in the protein coat of the virus makes a hole in the host cell, allowing the viral nucleic acids to enter and mix with the materials in the host cell.
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Reverse Transcription
It is a process that occurs once inside the host cell, it must first make viral DNA.
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Retrovirus
A virus that contains RNA as its genetic material.
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Reverse transcriptase
An polymerase enzyme in a retrovirus that uses the viral RNA template to synthesize complementary strands of DNA.
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Provirus
A newly formed DNA that integrates with the DNA of the host cell.
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HIV-1 Virus
Known to be the AIDS-causing agent.
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HIV
A retrovirus that infects and destroys T4 lymphocyte cells, which are involved in the immune response.