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144 Cards in this Set

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5' cap
A modified form of guanine nucleotide added onto the nucleotide at the 5' end of a pre-mRNA molecule.
A site
One of a ribosome’s three binding sites for tRNA during translation. The A site holds the tRNA carrying the next amino acid to be added to the polypeptide chain. (A stands for aminoacyl tRNA.)
alternative RNA splicing
A type of eukaryotic gene regulation at the RNA-processing level in which different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns.
amino acid
An organic molecule possessing both carboxyl and amino groups. Amino acids serve as the monomers of polypeptides.
aminoacyl-tRNA synthetase
An enzyme that joins each amino acid to the appropriate tRNA.
anticodon
A nucleotide triplet at one end of a tRNA molecule that recognizes a particular complementary codon on an mRNA molecule.
base-pair substitution
A type of point mutation
chaperonin
A protein molecule that assists in the proper folding of other proteins.
codon
A three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal
domain
(1) A taxonomic category above the kingdom level. The three domains are Archaea, Bacteria, and Eukarya. (2) An independently folding part of a protein.
E-site
One of a ribosome’s three binding sites for tRNA during translation. The E site is the place where discharged tRNAs leave the ribosome. (E stands for exit.)
endomembrane system
The collection of membranes inside and around a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles
exon
A sequence within a primary transcript that remains in the RNA after RNA processing
frameshift mutation
A mutation occurring when the number of nucleotides inserted or deleted is not a multiple of three, resulting in the improper grouping of the subsequent nucleotides into codons.
gene expression
The process by which DNA directs the synthesis of proteins or, in some cases, just RNAs
insertion
A mutation involving the addition of one or more nucleotide pairs to a gene.
intron
A noncoding, intervening sequence within a primary transcript that is removed from the transcript during RNA processing
messenger RNA (mRNA)
A type of RNA, synthesized using a DNA template, that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein.
missense mutation
A base-pair substitution that results in a codon that codes for a different amino acid.
mutagen
A chemical or physical agent that interacts with DNA and causes a mutation.
mutation
A change in the nucleotide sequence of an organism’s DNA, ultimately creating genetic diversity. Mutations also can occur in the DNA or RNA of a virus.
nonsense mutation
A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.
P site
One of a ribosome’s three binding sites for tRNA during translation. The P site holds the tRNA carrying the growing polypeptide chain. (P stands for peptidyl tRNA.)
point mutation
A change in a gene at a single nucleotide pair.
poly (A) tail
A sequence of 50 to 250 adenine nucleotides added onto the 3' end of a pre-mRNA molecule.
polyribosome (polysome)
A group of several ribosomes attached to, and translating, the same messenger RNA molecule.
primary transcript
An initial RNA transcript, also called pre-mRNA when transcribed from a protein-coding gene.
promoter
A specific nucleotide sequence in DNA that binds RNA polymerase, positioning it to start transcribing RNA at the appropriate place.
radiation
The emission of electromagnetic waves by all objects warmer than absolute zero.
reading frame
On an mRNA, the triplet grouping of ribonucleotides used by the translation machinery during polypeptide synthesis.
ribosomal RNA (rRNA)
The most abundant type of RNA, which together with proteins makes up ribosomes.
ribosome
A complex of rRNA and protein molecules that functions as a site of protein synthesis in the cytoplasm
ribozyme
An RNA molecule that functions as an enzyme, catalyzing reactions during RNA splicing.
RNA polymerase
An enzyme that links ribonucleotides into a growing RNA chain during transcription.
RNA processing
Modification of RNA transcripts, including splicing out of introns, joining together of exons, and alteration of the 5' and 3' ends
RNA splicing
After synthesis of a eukaryotic primary RNA transcript, the removal of portions (introns) of the transcript that will not be included in the mRNA.
signal peptide
A sequence of about 20 amino acids at or near the leading (amino) end of a polypeptide that targets it to the endoplasmic reticulum or other organelles in a eukaryotic cell.
signal-recognition particle (SRP)
A protein-RNA complex that recognizes a signal peptide as it emerges from a ribosome and helps direct the ribosome to the endoplasmic reticulum (ER) by binding to a receptor protein on the ER.
spliceosome
A large complex made up of proteins and RNA molecules that splices RNA by interacting with the ends of an RNA intron, releasing the intron and joining the two adjacent exons.
TATA box
A DNA sequence in eukaryotic promoters crucial in forming the transcription initiation complex.
template strand
The DNA strand that provides the pattern, or template, for ordering the sequence of nucleotides in an RNA transcript.
terminator
In bacteria, a sequence of nucleotides in DNA that marks the end of a gene and signals RNA polymerase to release the newly made RNA molecule and detach from the DNA.
transcription
A regulatory protein that binds to DNA and affects transcription of specific genes.
transcription factor
A regulatory protein that binds to DNA and affects transcription of specific genes.
transcription initiation complex
The completed assembly of transcription factors and RNA polymerase bound to a promoter.
transcription unit
A region of DNA that is transcribed into an RNA molecule.
transfer RNA (tRNA)
An RNA molecule that functions as an interpreter between nucleic acid and protein language by picking up specific amino acids and recognizing the appropriate codons in the mRNA.
translation
The synthesis of a polypeptide using the genetic information encoded in an mRNA molecule. There is a change of “language” from nucleotides to amino acids.
triplet code
A set of three-nucleotide-long words that specify the amino acids for polypeptide chains.
wobble
Flexibility in the base-pairing rules in which the nucleotide at the 5' end of a tRNA anticodon can form hydrogen bonds with more than one kind of base in the third position (3' end) of a codon.
5' cap
A modified form of guanine nucleotide added onto the nucleotide at the 5' end of a pre-mRNA molecule.
A site
One of a ribosome’s three binding sites for tRNA during translation. The A site holds the tRNA carrying the next amino acid to be added to the polypeptide chain. (A stands for aminoacyl tRNA.)
alternative RNA splicing
A type of eukaryotic gene regulation at the RNA-processing level in which different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns.
amino acid
An organic molecule possessing both carboxyl and amino groups. Amino acids serve as the monomers of polypeptides.
aminoacyl-tRNA synthetase
An enzyme that joins each amino acid to the appropriate tRNA.
anticodon
A nucleotide triplet at one end of a tRNA molecule that recognizes a particular complementary codon on an mRNA molecule.
base-pair substitution
A type of point mutation
chaperonin
A protein molecule that assists in the proper folding of other proteins.
codon
A three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal
domain
(1) A taxonomic category above the kingdom level. The three domains are Archaea, Bacteria, and Eukarya. (2) An independently folding part of a protein.
E-site
One of a ribosome’s three binding sites for tRNA during translation. The E site is the place where discharged tRNAs leave the ribosome. (E stands for exit.)
endomembrane system
The collection of membranes inside and around a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles
exon
A sequence within a primary transcript that remains in the RNA after RNA processing
frameshift mutation
A mutation occurring when the number of nucleotides inserted or deleted is not a multiple of three, resulting in the improper grouping of the subsequent nucleotides into codons.
gene expression
The process by which DNA directs the synthesis of proteins or, in some cases, just RNAs
insertion
A mutation involving the addition of one or more nucleotide pairs to a gene.
intron
A noncoding, intervening sequence within a primary transcript that is removed from the transcript during RNA processing
messenger RNA (mRNA)
A type of RNA, synthesized using a DNA template, that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein.
missense mutation
A base-pair substitution that results in a codon that codes for a different amino acid.
mutagen
A chemical or physical agent that interacts with DNA and causes a mutation.
mutation
A change in the nucleotide sequence of an organism’s DNA, ultimately creating genetic diversity. Mutations also can occur in the DNA or RNA of a virus.
nonsense mutation
A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.
P site
One of a ribosome’s three binding sites for tRNA during translation. The P site holds the tRNA carrying the growing polypeptide chain. (P stands for peptidyl tRNA.)
point mutation
A change in a gene at a single nucleotide pair.
poly (A) tail
A sequence of 50 to 250 adenine nucleotides added onto the 3' end of a pre-mRNA molecule.
polyribosome (polysome)
A group of several ribosomes attached to, and translating, the same messenger RNA molecule.
primary transcript
An initial RNA transcript, also called pre-mRNA when transcribed from a protein-coding gene.
promoter
A specific nucleotide sequence in DNA that binds RNA polymerase, positioning it to start transcribing RNA at the appropriate place.
radiation
The emission of electromagnetic waves by all objects warmer than absolute zero.
reading frame
On an mRNA, the triplet grouping of ribonucleotides used by the translation machinery during polypeptide synthesis.
ribosomal RNA (rRNA)
The most abundant type of RNA, which together with proteins makes up ribosomes.
ribosome
A complex of rRNA and protein molecules that functions as a site of protein synthesis in the cytoplasm
ribozyme
An RNA molecule that functions as an enzyme, catalyzing reactions during RNA splicing.
RNA polymerase
An enzyme that links ribonucleotides into a growing RNA chain during transcription.
RNA processing
Modification of RNA transcripts, including splicing out of introns, joining together of exons, and alteration of the 5' and 3' ends
RNA splicing
After synthesis of a eukaryotic primary RNA transcript, the removal of portions (introns) of the transcript that will not be included in the mRNA.
signal peptide
A sequence of about 20 amino acids at or near the leading (amino) end of a polypeptide that targets it to the endoplasmic reticulum or other organelles in a eukaryotic cell.
signal-recognition particle (SRP)
A protein-RNA complex that recognizes a signal peptide as it emerges from a ribosome and helps direct the ribosome to the endoplasmic reticulum (ER) by binding to a receptor protein on the ER.
spliceosome
A large complex made up of proteins and RNA molecules that splices RNA by interacting with the ends of an RNA intron, releasing the intron and joining the two adjacent exons.
TATA box
A DNA sequence in eukaryotic promoters crucial in forming the transcription initiation complex.
template strand
The DNA strand that provides the pattern, or template, for ordering the sequence of nucleotides in an RNA transcript.
terminator
In bacteria, a sequence of nucleotides in DNA that marks the end of a gene and signals RNA polymerase to release the newly made RNA molecule and detach from the DNA.
transcription
A regulatory protein that binds to DNA and affects transcription of specific genes.
transcription factor
A regulatory protein that binds to DNA and affects transcription of specific genes.
transcription initiation complex
The completed assembly of transcription factors and RNA polymerase bound to a promoter.
transcription unit
A region of DNA that is transcribed into an RNA molecule.
transfer RNA (tRNA)
An RNA molecule that functions as an interpreter between nucleic acid and protein language by picking up specific amino acids and recognizing the appropriate codons in the mRNA.
translation
The synthesis of a polypeptide using the genetic information encoded in an mRNA molecule. There is a change of “language” from nucleotides to amino acids.
triplet code
A set of three-nucleotide-long words that specify the amino acids for polypeptide chains.
wobble
Flexibility in the base-pairing rules in which the nucleotide at the 5' end of a tRNA anticodon can form hydrogen bonds with more than one kind of base in the third position (3' end) of a codon.
Albinism is caused by
a recessive allele of a pigmentation gene.
The information content of genes is
in the form of specific sequences of nucleotides along stands of DNA, the genetic material.
The DNA inherited by an organism leads to specific traits by dictating the synthesis of
proteins and of RNA molecules involved in protein synthesis.
Proteins are the link between
genotype and phenotype.
Gene expression is
the process by which DNA directs the synthesis of proteins (or, in some cases, just RNAs).
Expression of genes that code for proteins includes two stages
transcription and translation.
In 1909, British physician, Garrod
first to suggest that genes dictate phenotypes through enzymes that catalyze specific chemical reactions in the cell.
Garrod postulated that
the symptoms of an inherited disease reflect a person’s inability to make a particular enzyme, referred to them as “inborn errors of metabolism.”
Garrod gave one example of hereditary condition called alkaptonuria
in which the urine is black because it contains the chemical alkaptonuria, which darkens upon exposure to air, people with alkaptonuria have inherited an inability to make that enzyme.
1930, Beadle & Ephrussi speculated that in Drosophila
the synthesis of the pigments that give fruit flies their eye color, that each of the various mutations affecting eye color blocks pigment synthesis at a specific step by preventing production of the3 enzyme that catalyzes that step.
Beadle & Tatum began working with Neurospora crassa
bread mold that they bombarded the mold with X-rays, then looked among the survivors for mutants that differed in their nutritional needs from the wild type mold.
Wild type Neurospora has modest food requirements, can survive in the laboratory on a most support medium called agar
mixed only with inorganic salts, glucose, and the vitamin biotin. From this minimal medium, the mold cells use their
Identified mutant Neurospora was identified could not survive on the minimal medium, because they were unable to synthesize certain essential molecules from the minimal ingredients. To ensure survival, they were allowed to grow on a
complete growth medium, which consisted of minimal medium supplemented with all 20 amino acids and few other nutrients.
Samples from the mutants growing on the complete medium, distributed them to many different vials, each containing minimal medium plus a single additional nutrient. The particular supplement that allowed growth indicated the
metabolic defect.
Beadle & Tatum used additional tests to distinguish among three classes of arginine requiring mutants. Mutants in each class required a different set of compounds along the arginine synthesizing pathway, which ahs three step. Based on their results
they reasoned that each class must be blocked at a different step of the pathway because mutants in that classed lacked the enzyme that catalyzed the blocked step.
Beadle & Tatum’s results provide strong support for their
one gene-one enzyme hypothesis, which states that the function of a gene is to dictate the production of a specific enzyme.
Not all proteins are enzymes, proteins that are not enzymes are gene products, so biologists began to think in terms of one gene-one protein. However
many proteins are constructed from two or more different polypeptide chains, and each polypeptide is specified by its own gene.
Hemoglobin
the oxygen transporting protein of vertebrate red blood cells, is built from two kinds of polypeptides and thus two genes code for this protein – restated term was one gene-one polypeptide.
Many eukaryotic genes can code for a set of closely related polypeptides in a process called
alternative splicing.
Genes provide the instructions for making specific proteins, they do not
build a protein directly.
The bridge between DNA and protein synthesis is
the nucleic acid RNA.
RNA is chemically similar to DNA, except
that it contains ribose instead of deoxyribose as its sugar and has the nitrogenous base uracil rather than thymine.
Each nucleotide along a DNA strand has A, G, C, or T as its base, and each nucleotide along RNA strands has
A, G, C, or U as its base.
RNA usually consists of a
single strand.
Genes are typically hundreds or thousands of nucleotides long, each having a
specific sequence of bases.
Each polypeptide of a protein also has monomers arranged in a particular linear order (the proteins primary structure), but its monomers are
amino acids.
Nucleic acids and proteins contain information in different languages, getting from DNA to protein requires two major stages
transcription and translation.
Transcription
is the synthesis of RNA under the direction of DNA. Both nucleic acids use the same language, and the information is si9mply transcribed, or copied, from one molecule to the other.
DNA strand serves as a template in DNA replication and, it also can serve as a temple for assembling a
complementary sequence of RNA nucleotides.
For a protein coding gene, the resulting RNA molecule is
a transcript of the gene’s protein building instructions and it can be sent out in multiple copies.
messenger RNA (mRNA)
carries a genetic message from the DNA to the protein synthesizing machinery of the cell.
Transcription is the general term for
the synthesis of any kind of RNA on a DNA template.
Translation is
the synthesis of a polypeptide, which occurs under the direction of mRNA.
During translation, there is a change in the language, cell must translate the base sequence of an mRNA molecule into the amino acid sequence of a polypeptide. The site of translation are
ribosomes, complex particles that facilitate the orderly linking of amino acids into polypeptide chains.
Transcription and translation occur in all organisms, and the basic mechanics are the similar for bacteria and eukaryotes. There is an important difference in the flow of genetic information within the cells. Because bacteria do not have a nuclei
their DNA is not segregated from ribosomes, and other protein synthesizing equipment and this lack of segregation allows translation of mRNA to begin while its transcription is still in progress.
Translation is
the synthesis of a polypeptide, which occurs under the direction of mRNA.
During translation, there is a change in the language, cell must translate the base sequence of an mRNA molecule into the amino acid sequence of a polypeptide. The site of translation are
ribosomes, complex particles that facilitate the orderly linking of amino acids into polypeptide chains.
Transcription and translation occur in all organisms, and the basic mechanics are the similar for bacteria and eukaryotes. There is an important difference in the flow of genetic information within the cells. Because bacteria do not have a nuclei
their DNA is not segregated from ribosomes, and other protein synthesizing equipment and this lack of segregation allows translation of mRNA to begin while its transcription is still in progress.
The process in eukaryotic cells
the nuclear envelope separates transcription from translation in space and time. Transcription happens in the nucleus, and mRNA is transported in the cytoplasm, where translation occurs.
Before leaving the nucleus, eukaryotic RNA
transcripts from protein coding genes are modified in ways to produce the final function mRNA.
The transcription of a protein coding eukaryotic gene results in
pre mRNA and further processing yields the finished mRNA.
The initial RNA transcript from any gene, including those coding for RNA that is not translated to protein, is more generally called
a primary transcript.
Directional flow of genetic information
DNA → RNA → protein, this is the concept dubbed the central dogma by Crick in 1956.
1970s scientist discovered that some RNA molecules can act as templates for DNA, but this is
a rare exception and does not invalidate the idea that, in general, genetic information flows from DNA to RNA to protein.