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Biology 12 > Unit 3: Molecular Genetics > Flashcards

Unit 3: Molecular Genetics Flashcards

1
Q

bacteriophages (phage)

A

A virus that infects bacterial cells; also called a “phage”

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2
Q

purine

A

The larger of the 2 general kinds of nucleotide base found in DNA and RNA; a nitrogenous base with a double-ring structure, such as a adenine or guanine

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3
Q

pyrimidine

A

The smaller of 2 general kinds of nucleotide base found in DNA and RNA; a nitrogenous base with a single-ring structure, such as cytosine, thymine, or uracil.

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4
Q

chromosome

A

The vehicle by which hereditary information is physically transmitted from one generation to the next/ in a bacterium, the chromosome consists of a single naked circle of DNA; in eukaryotes, each chromosome consists of a single linear DNA molecule and associate proteins.

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5
Q

phosphodiester bond

A

The linkage between two sugars in the backbone of a nucleic acid molecule; the phosphate group connects the pentose sugars through a pair of ester bonds.

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6
Q

base-pairs

A

A complementary pair of nucleotide bases, consisting of a purine and pyrimidine.

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7
Q

DNA polymerase

A

A class of enzymes that all synthesize DNA from a preexisting template. All synthesize only in the 5’-to-3’ direction, and require a primer to extend.

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8
Q

DNA polymerase I (Pol I)

A

Erases primer and fills gap

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9
Q

DNA polymerase III (Pol III)

A

Synthesizes DNA

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10
Q

endonuclease

A

An enzyme capable of cleaving phosophodiester bonds between nucleotides located internally in DNA strand.

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11
Q

exonuclease

A

An enzyme capable of cutting phosphodiester bonds between nucleotides located at an end of a DNA strand. This allows sequential removal of nucleotides from the end of DNA.

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12
Q

helicase

A

Any of a group of enzymes that unwind the two DNA strands in the double helix to facilitate DNA replication.

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13
Q

supercoiling

A

The coiling in space of double-stranded DNA molecules due to torsional strain, such as occurs when the helix is unwound.

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14
Q

topoisomerase

A

Any class of enzymes that can change the topological state of DNA to relieve torsion caused by unwinding.

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15
Q

DNA gyrase

A

A topoisomerase involved in DNA replication; it relieves the torsional strain caused by unwinding the DNA strands.

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16
Q

leading strand

A

The DNA strand that can be synthesized continuously from the origin of replication.

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17
Q

lagging strand

A

The DNA strand that must be synthesized discontinuously because of the 5’-to-3’ directionality of DNA polymerase during replication, and the antiparallel nature of DNA.

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18
Q

Okazaki fragments

A

A short segment of DNA produced by discontinuous replication elongating in the 5’-to-3’ direction away from the replication.

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19
Q

replication fork

A

The Y-shaped end of a growing replication bubble in a DNA molecule undergoing replication.

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20
Q

DNA ligase

A

The enzyme responsible for formation of phosphodiester bonds between adjacent nucleotides in DNA.

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21
Q

replisome

A

The macromolecular assembly of enzymes involved in DNA replication; similar to the ribosome in protein synthesis.

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22
Q

Primase

A

The enzyme that synthesizes the RNA primers required by DNA polymerase.

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23
Q

Single-strand binding protein

A

Stabilizes single-stranded regions

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24
Q

telomere

A

A specialized nontranscribed structure that caps each end of a chormosome.

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25
telomerase
An enzyme that synthesizes telomerases on eukaryotic chromosomes using an internal RNA template.
26
central dogma of molecular biology
DNA --> RNA ---> protein
27
transcription
The enzyme-catalyzed assembly of an RNA molecule complementary to a strand of DNA.
28
translation
The assembly of a protein on the ribosomes, using mRNA to specify the order of amino acids.
29
retroviruses
An RNA virus. When a retrovirus enters a cell, a viral enzyme (reverse transcriptase) transcribes viral RNA into duplex DNA, which the cell's machinery then replicates ad transcribes as if it were its own.
30
reverse transcriptase
A viral enzyme found in retroviruses that is capable of converting their RNA genome into a DNA copy.
31
template strand
The DNA strand that is used as a template in transcription. This strand is copied to produce a complementary mRNA transcript.
32
coding strand
The strand of a DNA duplex that is the same as the RNA encoded by a gene. This strand is not used as a template in transcription, it is complementary to the template.
33
messenger RNA (mRNA)
The RNA transcribed from structural genes; RNA molecules complementary to a portion of one strand of DNA, which are translated by the ribosomes to form protein.
34
ribosomal RNA (rRNA)
A class of RNA molecules found, together with characteristic proteins, in ribosomes; transcribed from the DNA of the nucleolus.
35
transfer RNA (tRNA)
A class of small RNAs with 2 functional sites; a one site, an "activating enzyme" adds a specific amino acid, while the other site carries the nucleotide triplet (anticodon) specific for that amino acid.
36
small nuclear RNA (smRNA)
In eukaryotes, a small RNA sequence that, as part of a small nuclear ribonucleoptrotein complex, facilitates recognition and excision of introns by base-paring with the 5'end of an intron or at a branch site of the same intron.
37
SRP RNA (signal recognition particle)
In eukaryotes, a cytoplasmic complex of proteins that recognizes and binds to the signal sequence of a polypeptide, and then docks with a receptor that forms a channel in the ER membrane. In this way the polypeptide is released into the lumen of the ER.
38
Micro-RNA (micro-RNA / miRNA)
A class of RNAs that are very short and only recently could be detected.
39
reading frame
The correct succession of nucleotides in triplet codons that specify amino acids on translation. The reading frame is established by the first codon in the sequence as there are no spaces in the genetic code.
40
frameshift mutation
A mutation in which a base is added or deleted form the DNA sequence. These changes alter the reading frame downstream of the mutation.
41
stop codon
Any of the 3 codons UAA, UAG, and UGA, that indicate the point at which mRNA translation is to be terminated.
42
start codon
The AUG triplet, which indicates the site of the beginning of mRNA translation; this codon also codes for the amino acid methionine.
43
RNA polymerase
An enzyme that catalyzes the assembly of an mRNA molecule, the sequence of which is complementary to a DNA molecule used as a template.
44
promoter
A DNA sequence that provides a recognition and attachment site for RNA polymerase to begin the process of gene transcription; it is located upstream from the transcription start site.
45
transcription unit
The region of DNA between a promoter and a terminator.
46
transcription bubble
The region containing the RNA polymerase, the DNA template, and the RNA transcript, so called because of the locally unwound "bubble" of DNA.
47
operon
A cluster of adjacent structural genes transcribed as a unit into a single mRNA molecule.
48
RNA polymerase I
Transcribes rRNA
49
RNA polymerase II
Transcribes mRNA
50
RNA polymerase III
Transcribes tRNA
51
TATA box
In eukaryotes, a sequence located upstream of the transcription start site. The TATA box is one element of eukaryotic core promoters for RNA polmerase II.
52
transcription factors
One of a set of proteins required for RNA polymerase to bind to a eukaryotic promoter region, becoming stabilized, and being the transcription process.
53
primary transcript
The initial mRNA molecule copied from a gene by RNA polymerase, containing a faithful copy of the entire gene, including introns as well as exons.
54
5' cap
In eukaryotes, a structure to the 5' end of an mRNA consisting of methylated GTP attached by a 5' to 5' bond. The cap protects this end from degration and is involved in the initiation of translation.
55
3' poly-A tail
In eukaryotes, a series of 1-200 adenine residues added to the 3' end of an mRNA; the tail appears to enhance the stability of the mRNA by protecting it from degradation.
56
introns
Proportion of mRNA as transcribed fom eykaryotic DNA that is removed by enzymes before the mature mRNA is translated into protein.
57
exons
A segment of DNA that is both transcribed into RNA and translated into protein.
58
pre-mRNA splicing
In eukaryotes, the process by which introns are removed from th primary transcript to produce mature mRNA; pre-mRNA splicing occurs in the nucleus.
59
small nuclear ribonucleoprotein particles (snRNPs "snurps")
In eukaryotes, a complex composed of dnRNA and proteins that clusters together with other snRNPs to form the spliceosome which removes introns from the primary transcript.
60
spliceosome
In eukaryotes, a complex composed of multiple snRNPs and other associated proteins that is responsible for excision of introns and joining of exons to convert the primary transcript into the mature mRNA.
61
alternative splicing
In eukaryotes, the production of different mRNAs from a single primary transcript by including different sets of exons.
62
aminoacytl-tRNA synthetase
Any of a group of enzymes that attach specific amino acids to the correct tRNA during the tRNA-charging reaction. Each of the 20 amino acids has a corresponding enzyme.
63
acceptor stem
The 3' end of a tRNA molecule; the proportion that amino acids become attached to during the tRNA charging reaction.
64
anticodon
The three-nucleotide sequence at the end of a transfer RNA molecule that is complementary to, and base-pairs with, an amino-acid-specifying codon in messenger RNA.
65
charging reaction
The reaction by which an aminoacyl-tRNA synthetase attaches a specific amino acid to the correct tRNA using energy from ATP.
66
peptidyl transferase
In translation, the enzyme responsible for catalyzing the formation of a peptide bind between each new amino acid and the previous amino acid in a growing polypeptide chain.
67
initiation factor
One of the several proteins involved in the formation of an initiation complex in prokaryote polypeptide synthesis.
68
initiator tRNA
A tRNA molecule involved in the beginning of translation. In prokaryotes, the initiator tRNA is charged with N-formylmethionin (tRNA^fMet); in eukaryotes, the tRNA is charged simply with methionine.
69
ribosome-binding sequence (RBS)
In prokaryotes, a conserved sequence at the 5' end or mRNA that is complementary to the 3' end of a small subunit rRNA and helps to position the ribosome during initiation.
70
elongation factor (EF-Tu)
In protein synthesis in E. Coli, a factor that binds to GTP and to a charged tRNA to accomplish binding of the charged tRNA to accomplish binding of the charged tRNA to the A site of the ribosome, so that elongation of the polypeptide chain can occur.
71
chromosomal mutation
Any mutation that affects chromosomal structure.
72
deletion
A mutation in which a portion of a chomosome is lost; if too much information is lost, the deletion can be fatal.
73
duplication
A mutation in which a portion of a chormosome is duplicated; if the duplicated region does not lie within a gene, the duplication may have no effect.
74
inversion
A reversal in order of a segment of a chromosome.
75
translocation
In genetics, the interchange of chormosome segments between nonhomologous chromosomes.
76
chromatin
The complex of DNA and proteins of which eukaryotic chromosomes are composed; chromatin is highly uncoiled and diffuse in interphase nuclei, condensing to form the visible chromosome in prophase.
77
nucleosome
A complex consisting of a DNA duplex wound around a core of eight histone proteins.
78
histone proteins
Any of the 8 proteins with an overall positive charge that associate in complex. The DNA duplex coils around a core of 8 histone proteins, help by its negatively charged phosphate groups, forming a nucleosome.
79
chromatid
One of the two daughter strands of a duplicated chromosome that is joined by a single centromere.
80
genotype
The genetic constitution underying a single trait of set of traits.
81
phenotype
The realized expression of the genotype; the physical appearance of functional expression of a trait.
82
codon
The basic unit of the genetic code; a sequence of 3 adjacent nucleotides in DNA or mRNA that codes for one amino acid.
83
mutagen
A substance that causes a mutation or increase the number of mutations above the typical level.
84
excision repair
A nonspecific mechanism to repair damage to DNA during synthesis. The damages or mismatched region is excides, and DNA polymerase replaces the region removed.
85
nuclein
The new substance Swiss chemist, Friedrick Miescher, discovered in 1896. He discovered DNA when he extracted a substance from the nuclei of human cells an fish sperm. The composition of the substance had different levels of nitrogen and phosphorus, so he was convinced that it was a new biological substance.
86
initiation
Beginning
87
elongation
Middle
88
Termination
End
89
replicon
In prokaryotic cells, there is one single origin of replication as the chromosomes are circular called a replicon.
90
β-subunit/β-clamp/sliding clamp
A sliding clamp that hols the DNA polymerase III attached to the template strand and continually synthesize DNA.
91
mutation
any change to a heritable material.
92
frameshift mutation
deletion or addition of DNA that alters ow codons are read, which causes a nonfunctional protein (although not all the time).
93
sense mutation
Substitution of the wrong nucleotides, which causes the same amino aid to be present in a polypeptide chain.
94
missense mutation
Substitution of the wrong nucleotides, which causes the wrong amino acid to be present in a polypeptide chain (ex. sickle cell anemia)
95
nonsense mutation
substitution of the wrong nucleotides, which causes a premature stop codon
96
thymine dimer
exposure to UV light forms covalent bonds between Thymine residues. This can cause other mutations or negatively effect replication.
97
gene expression
A term that refers to the process by which DNA directs the synthesis of proteins.
98
one gene/one polypeptide hypothesis
Based on the work of Beadle & Tatum, it was concluded that each gene codes for one enzyme (or protein). We now know that an enzyme consists of multiple subunits and so we call this hypothesis the one gene/one polypeptide hypothesis.
99
mature mRNA
In eukaryotes, the mRNA must be processed before it can leave the nucleus and produce a protein. The processed mRNA.
100
anticodon loop
A stretch of nucleotides that is complimentary to the mRNA codon.
101
release factor/termination factor
In translation, elongation will continue until one of the stop codons is reached. These codons do not bind to tRNA, but instead bind proteins called release factors or terminations factors.

Biology 12 (7 decks)

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