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59 Cards in this Set
- Front
- Back
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In terms of genetics and related processes, what makes eukaryotic cells different from prokaryotic cells?
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-Genomes are larger
-Genomes have more regulatory sequences -Much of eukaryotic DNA is noncoding -Multiple chromosomes -Multiple copies for many eukaryotic genes; large amount of non-essential DNA -Genes are interrupted by non-coding DNA, which is transcribed -Eukaryotic genes in nucleus. Translation in cytoplasm -Polycistronic mRNAs rare -In multicellular organisms, gene expression is development and tissue specific |
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Where is pre-mRNA processed to mature mRNA? and where does it go after that?
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It is processed in the nucleus and then transported to the cytoplasm.
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What compound translates mRNA into proteins? Where does this occur?
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-ribosome
-cytoplasm |
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What characteristics describe Satellite DNA?
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5-50 bp in length and repeated 105 to 106 times. Usually present at the centromere.
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What characteristics describe Minisatellites?
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12-100 bp in length; repeated a variable number of times; used for DNA fingerprinting during the 1990's.
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What characteristics describe Microsatellites?
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1-5 bp repeated sequences; present in 10-50 copies; very useful genetic markers; Used in modern DNA fingerprinting.
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What are the names for three highly repetitive DNA sequences, present in large copy number?
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-Satellite DNA
-Minisatellites -Microsatellites |
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What do Telomeres do?
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Maintain the length and integrity of the chromosomes.
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What two types of RNA account for 75% or more of stable DNA in a cell?
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rRNA and tRNA
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Where is it thought that tandem array of genes arise from?
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gene duplication during evolution
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During active cell division, a massive amount of _____ is transcribed from the _____ region of the genome.
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-rRNA
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What are the four different types of transposons in eukaryotic cells?
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-SINEs (short interspersed elements)
-LINEs (long interspersed elements) -Retrotransposons -DNA transposons |
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Describe SINEs.
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short interspersed elements up to 500 bp in length
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Describe LINEs.
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long interspersed elements up to 7000 bp in length which may code for protein
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Describe Retrotransposons.
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May encode the enzymes required for their movement. Movement involves an RNA copy. The 300 bp Alu element accounts for 11% of the human genome, with a million scattred copies.
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Describe DNA transposons.
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move to a new spot without replicating and without an RNA intermediate
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What are some of the consequences of transposons?
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-When a transpon moves into a functional gene, mutation can result.
-When in the germ line, the mutation can be inherited. When in a somatic cell, cancer might result. -Transposition contributes to genetic variation and evolution. |
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What's the significance of promoters and terminators?
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-Promoters occur before genes (on DNA) to signal the start site for transcription.
-Terminators at the opposite end of the gene are stop sites for RNA synthesis. |
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What's the difference between exons and introns on DNA?
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-Exons are stretches of DNA whose transcripts are present in mature mRNA.
-Introns are stretches of DNA whose transcripts are absent from mature mRNA product, yet they are present on pre-mRNA |
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What are mRNA's first transcripted as?
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larger precursor mRNA's (pre-mRNA)
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What is an important research technique for gene isolation and intron discovery? Describe it.
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-Hybridization of DNA and RNA
-mRNA can form a hybrid with a DNA template strand by complementary base pairing. |
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The extra DNA in genes was first identified by _________ of DNA-mRNA hybrids.
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electron microscopy
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What is an "R-loop"?
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Hybridization of spliced mRNA with double stranded DNA.
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What method, other than the "R-loop," can be used to find the introns within a gene?
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Hibridization of spliced mRNA with the coding strand of DNA (single-stranded DNA).
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Name some of the places where introns occur (or may not occur).
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-mRNA, tRNA, rRNA genes of eukaryotic nucleus
-chloroplast and mitochondrial DNA -rare in prokaryote and archebacterial genes |
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Non-identical genes for mRNA form multigene famiilies. Name some of the places where such families are present.
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-Hemoglobin subunit genes are a multigene family in mammalian cells.
-Mutations may accumulate in duplicated genes. -Active genes encode globin subunits specific for different stages of mammalian development: i.e. embryo, young, and adult organisms. -Human Chromosome 16: alpha globin genes -Human Chromosome 11: beta globin genes |
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Different ______ are expressed at different times during human development, and in different cell types.
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genes
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Define Heterogeneous Nuclear RNA.
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They are Primary Precursor mRNA transcripts, termed hnRNA.
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What does are the processing events that hnRNA goes through to become mature and translatabe mRNA? Where does this occur?
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1. a 5'-cap is added
2. a 3'-poly [A] tail is added 3. splicing -This occurs in the nucleus of a cell |
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During processing, what is attached to the 5' end of hnRNA? how is it attached?
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-a modified GTP
-It attaches covalently |
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What are some of the functions of a 5' cap?
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It's involved in ribosome binding and mRNA stability.
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What is attached to the 3' end of hnRNA during processing?
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A poly [A] tail of 100-200 adenine nucleotides.
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Are poly [A] tails coded for in DNA?
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No.
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Are poly [A] tails and G-caps present on all RNAs?
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No.
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What occurs during the splicing of hnRNA?
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Removal of introns and joining of exons.
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Where to most mature mRNA's go after processing?
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the cytoplasm
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What is a spliceosome?
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A spliceosome is a large, nuclear-located RNA-protein complex that catalyzes RNA SPLICING.
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________ participate directly in splicing reactions via RNA-RNA interactions.
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snRNAs
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snRNPs are formed when...
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snRNAs complex with proteins.
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Spliceosomes are formed when...
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6 major snRNPs assemble on pre-mRNA.
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Describe the two-step splicing reaction for hnRNAs.
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Step 1: Cleavage of 5'exon-intron boundary and formation of intron-lariat; 1st phosphodiester transfer reaction
Step 2: Joining of 5' and 3' exons, and release of intron as lariat; 2nd phosphodiester transfer reaction |
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Describe alternate splicing?
How does it work? |
-The process by which different mRNAs and proteins can form from a single gene.
-usually, certain exons are left out of the mature mRNA, depending on what tissue or developmental stage it is specified for. |
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Is alternate splicing regulated? If so, what's an example?
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-Yes.
-Splicing of a precursor mRNA can vary by tissue or developmental stage. |
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How is transcription controlled in eukaryotes?
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Transcription factors bind DNA.
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Eukaryotic promoter sequences are more ________ than in prokaryotes.
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complex
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A transcription complex positions RNA polymerase at the beginning of a eukaryotic gene. The complex contains four kinds of proteins. What are they, and what do they do?
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1. Basal factorts, i.e. TATA-binding proteins
2. Coactivators, linking basal factors to activators 3. Activators, which bind at distant enhancer sites on DNA 4. Repressors, binding to silencer sites on DNA preventing activator binding |
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What do enhancers and silencers do, and where are they in relation to the promoter?
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-Enhancers and silencers are DNA sequence elements located at a distance from the promoter, up to 20,000 bp.
-They stimulate specific promoters. -They bind transcriptional activator proteins. |
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Negative regulatory elements are called ________. They turn off transcription by binding proteins termed _________.
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-silencers
-repressors |
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Specifically, what are activators?
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Activators are proteins with surfaces for DNA binding, and one or more surfaces for binding other transcription proteins.
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Activators have motifs to bind in the ________. What are the five main motifs, and what do they do?
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-major groove
1. helix-turn-helix -These proteins regulate genes involved in development. 2. homeodomain -n/a 3. luecine zipper -These proteins regulate cell division genes. 4. zinc finger -These proteins are steroid hormone receptors. 5. helix-loop-helix -These proteins regulate immune system genes. |
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Draw simple diagrams for the supposed shapes of these activators (if known).
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*check in book
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How can a protein recognize a specific DNA sequence?
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-The edges of the DNA base pairs protrude into the Major Groove of DNA
-Each base pair has unique recognition elements. |
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What are the four recognition elements unique to each base pair?
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1. Hydrogen bond donors
2. Hydrogen bond acceptors 3. Hydrophobic methyl groups 4. Hydrogen: non-hydrogen bonding |
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What is Coordinate Regulation of gene expression?
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Coordinate Regulation involves a coordinate, or location on the DNA that transcribes signal proteins that are used in turning on expression of multiple genes.
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In what ways is coordinate regulation used for multiple genes?
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-Genes may be on different chromosomes.
-Coordinately expressed genes may have the same regulatory sequences which bind the same regulatory protein. -A single signal may cause the synthesis of a transcriptional regulator for many genes. |
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How are different combinations of activators and enhancers used?
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-Activators often bind to different genes in different combinations to activate those genes.
-Activators can help to activate one gene in one cell and a different gene in a different cell. |
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SG:
RNAs that catalyze BIOLOGICAL REACTIONS, such as self-splicing introns, are known as: |
Ribozymes.
-A ribozyme is an RNA molecule that can catalyze a biochemical reaction. |
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Polycistronic mRNAs are very common in ___________, but are rare in ____________.
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-prokaryotes
-eukaryotes |
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What is reverse transcription?
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Reverse transcription is the enzymatic synthesis of DNA from an RNA template by the enzyme reverse transcriptase.
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