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44 Cards in this Set
- Front
- Back
Chromosome Territories |
Regions of the nucleus preferentially occupied by particular chromosomes |
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Transcription Factories |
Hotspots for gene transcription where all the machinery for transcription are located (e.g., RNA polymerase) |
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Nucleosome |
A basic unit of DNA packaging in eukaryotes, consisting of a segment of DNA wound in sequence around eight histone protein cores |
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Interchromosomal Domains |
Channels between chromosomes that contain little or no DNA |
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"Closed" Chromatin |
The tight association of DNA with nucleosomes and other chromatin-binding proteins that inhibits access of the DNA to the proteins involved in many functions including transcription |
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"Open" Chromatin |
"Open" to transcription regulatory factors and enzymes such as RNA polymerases |
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Histone Acetyltransferase |
Enzyme that catalyzes histone acetylation to result in "open" chromatin conformation |
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Acetylation |
Decreases the positive charge on histones, resulting in a reduced affinity of the histone for DNA. In turn, this may assist the formation of open chromatin conformations which would allow the binding of transcription regulatory proteins to the DNA |
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Histone Deacetylases |
Remove acetyl groups from the N-terminus to result in "closed" chromatin conformation |
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Chromatin Remodelling Complexes |
Multi-subunit complexes that use ATP to move and rearrange nucleosomes along the DNA to make regions of the chromosome accessible to transcription regulatory proteins |
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CpG Islands |
CpG rich regions of the genome where methylation tends to occur |
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Hemimethylated |
New strand is not methylated, old strand is methylated |
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Maintenance Methylation |
Process that methylates non-methylated daughter strand as well |
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Genetic Imprinting |
- Epigenetic phenomenon by which certain genes are expressed in a parent-of-origin specific manner - An imprinted allele is said to be "silenced" |
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Promoter Elements |
Short nucleotide sequences within promoters that bind specific regulatory factors |
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Core Promoter |
Determines the accurate initiation of transcription by RNAP II |
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Proximal Promoter Elements |
Those that modulate the efficiency of basal levels of transcription |
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Focused Promoter |
- Specifies transcription initiation at a single specific nucleotide (the transcription start site) - Associated with genes whose transcription levels are highly regulated |
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Dispersed Promoters |
- Promoters that direct initiation from a number of weak transcription start sites located over a 50-100 nucleotide region to produce multiple transcripts - Common in vertebrates - Associated with genes that are transcribed constitutively |
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Enhancer |
- DNA sequence that regulates transcription by increasing transcriptional level by 1000 - 10 000 fold - Can be located on either side of a gene, at some distance from the gene, or within the gene - Cis-acting - Both front and reverse orientation of the enhancer can be understood - Placing an enhancer in front of a new gene will result in the enhancing of that gene |
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Silencer |
- DNA sequence that acts upon eukaryotic genes to repress the level of transcription initiation - Cis-acting |
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Activator |
A transcription factor that increases levels of transcription |
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Repressor |
A transcription factor that reduces levels of transcription |
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General Transcription Factors |
Transcription factors necessary for basal levels of transcription |
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Regulatory Transcription Factors |
Transcription factors that influence the ability of RNA polymerase to transcribe |
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DNA-Binding Domain |
- Region of transcription factor that binds to specific DNA sequences present in the cis-acting regulatory site - Characteristic 3D structures are: 1) helix-turn-helix motif 2) zinc finger motif 3) basic leucine zipper motif |
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Helix-Turn-Helix Motif |
- One characteristic 3D structure of a DNA-binding domain of both eukaryotic and prokaryotic transcription factors - "Turn" of several amino acids |
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Zinc-Finger Motif |
- One characteristic 3D structure of a DNA-binding domain of transcription factors - Recognition helix often has positively charged amino acids that help it bind to negatively charged DNA - Beta sheets and alpha sheets are connected by zinc |
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Basic Leucine Zipper Motif |
- One characteristic 3D structure of a DNA-binding domain of transcription factors - Contains a region called a leucine zipper that maintains a coil formation |
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Alternative Splicing |
Generation of different forms of mRNA from identical pre-mRNA molecules, so that expression of one gene can give rise to a number of proteins, with similar or different functions |
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AU - Rich Element |
- Stretch of A and U ribonucleotides located in the 3' untranslated regions of mRNAs that have short, regulated half lives - Recruit degrading protein complexes |
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p53 Protein |
- Important example of post translational regulation - Essential to protect normal cells from the effects of DNA damage and other stresses - Transcription factor that increases the transcription of a number of genes whose products are involved in cell-cycle arrest, DNA repair and apoptosis - Quantity increases when the cell is under stress - Ubiquine marks p53 for degradation under normal cellular conditions |
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Decapping Enzymes |
Enzymes that remove the 7-methylguanosine cap rendering the mRNA unstable |
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Nonsense-Mediated Decay |
- Example of endonucleolytic cleavage that determine mRNA stability - Occurs when translation terminates at premature stop codons - Endonucleases attack the mRNA near the stop codon, leaving unprotected ends that are degraded by exonucleases |
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Small Interfering RNAs (siRNA) |
- Involved in RNA-induced gene silencing - Short, double-stranded RNA molecules derived from longer RNA molecules that are linear, double-stranded and located in the cell cytoplasm - In nature, arise as a result of viruses or the expression of transposons (which synthesize double-stranded RNA during their life cycles) |
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Dicer |
- Enzyme complex that cleaves RNAs to make siRNA - Recognizes double-stranded RNA - Used in the lab |
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Micro RNAs (miRNA) |
- Involved in RNA-induced gene silencing - Short, double-stranded RNA molecules derived from single-stranded RNAs that are transcribed within the nucleus from the cel's own genome and that contain a double-stranded stem-loop structure (stem loop is cleaved and its fragments are exported our of the nucleus) |
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RNA-Induced Silencing Complex |
Enzyme complex involved in RNA-induced gene silencing - Associates with siRNA or miRNA to denature short, double-stranded RNA and degrade the sense strand - As an RNA-RISC complex, it seeks out mRNA molecules that are complementary to the anti-sense strand to cleave or bind them - mRNA molecules that are not quite complementary to the anti-sense strand are bound to inhibit translation |
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RNA-Induced Transcription Silencing Complex |
- Enzyme complex involved in RNA-induced silencing - Associates with siRNA or miRNA and targets specific gene promoters or larger regions of chromatin to recruit chromatin modification enzymes |
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Antigen |
A molecule, usually a protein, that brings about an immune response |
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Immunoglobulin (Antibody) |
- Synthesized by B lymphocytes (B cells) that undergo development and maturation in the bone marrow' - Molecules consist of 4 polypeptide chains - two identical light chains and two identical heavy chains - Y-shaped |
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Constant Region |
Region at the C-terminus of light and heavy chains of an immunoglobulin molecule |
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Variable Region |
- Region at the N-terminus of light and heavy chains of an immunoglobulin molecule - 4 variable regions form a unique structure that recognizes one specific antigen |
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B Cell |
- B lymphocyte - Type of blood cell that synthesizes immunoglobulins - Each B cell synthesizes only one type of immunoglobulin |