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Chapter 19
Vocabulary & Key Concepts
33
Biology
Undergraduate 1
01/26/2014

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Term
differential gene expression
Definition
responsible for creating different cell types, arranging them into their tissues, & coordinating their activity to form the multicellular society we call an individual
Term
chromatin
Definition
a structure in eukaryotes created from DNA being wrapped around proteins
Term
chromatin remodeling
Definition
before transcription can begin in eukaryotes, the stretch of DNA containing the promoter must be released from tight interactions with proteins, so that RNA polymerase can make contact with the promoter
Term
RNA processing
Definition
the steps required to produce a mature, processed mRNA from a primary RNA transcript
Term
histone code hypothesis
Definition
particular combinations of histone modifications set the state of chromatin condensation for a particular gene
Term
histone acetyltransferases/HATs
Definition
add acetyl groups to the positively charged lysine residues in histones
Term
histone deacetylases/HDACs
Definition
remove acetyl groups from histones
Term
acetylation of histones usually results in _____
Definition
decondensed chromatin, a state associated with active transcription
Term
epigenetic inheritance
Definition
patterns of inheritance that are due to something other than differences in DNA sequences
Term
promoter
Definition
a site in DNA where RNA polymerase binds to initiate transcription
Term
TATA box
Definition
a conserved sequence that serves as a binding site for proteins needed to start transcription
Term
promoter-proximal elements
Definition
regulatory sequences that are located close to the promoter & bind regulatory proteins
Term
enhancers
Definition
regulatory sequences that are far from the promoter & activate transcription
Term
5 key points about enhancers
Definition
1. can be more than 100,000 bases away from the promoter
2. there are many types
3. most genes have more than one
4. usually have binding sites for more than one protein
5. can work even if their normal 5' -> 3' orientation is flipped or are moved to a new location in the vicinity of the gene
Term
transcriptional activators
Definition
regulatory proteins that begin transcription when bound to enhancers
Term
silencers
Definition
regulatory sequences that are similar in structure & share key characteristics with enhancers but work to inhibit transcription
Term
repressors
Definition
regulatory proteins that bind to silencers to shut down transcription
Term
basal transcription factors
Definition
proteins that interact with the promoter & are not restricted to particular genes or cell types
Term
4 steps: transcription initiation
Definition
1. chromatin remodeling
2. exposure of promoter & regulatory sequences
3. assembly of proteins
4. DNA looping allows Mediator to connect DNA-bound activators & basal transcription factors
Term
4 gene control mechanisms
Definition
1. splicing RNAs in various ways
2. modifying the life san of mRNAs
3. altering the rate at which translation is initiated
4. activating or inactivating proteins after translation has occurred
Term
spliceosomes
Definition
macromolecular machines that splice primary RNAs
Term
alternative splicing
Definition
splicing the same primary RNA transcript in different ways to produce different mature mRNAs & thus different proteins
Term
RNA interference
Definition
when a tiny, single-stranded RNA held by a protein complex binds to a complementary sequence in an mRNA which unleashes either the destruction of the mRNA or a block to the mRNAs translation
Term
6 steps: RNA interference
Definition
1. transcription of a microRNA gene
2. precursor microRNA (miRNA) formed by initial processing of transcript in nucleus
3. double-stranded miRNA formed when enzyme in cytoplasm trims the RNA hairpin into a short double-stranded RNA
4. mature miRNA formed when double-stranded miRNA binds to RISC protein complex & one strand is degraded
5. miRNA, held by RISC, binds to complementary sequence on target mRNA
6. RISC either cuts mRNA or prevents the mRNA from being translated
Term
proteasome
Definition
recognizes proteins that have a ubiquitin tag & cuts them into short segments
Term
bacteria VS eukaryotes: chromatin remodeling
Definition
b: limited packaging of DNA; remodeling not a major issue in regulating gene expression
e: extensive packaging of DNA; chromatin must be decondensed for transcription to begin
Term
bacteria VS eukaryotes: transcription
Definition
b: positive & negative control by regulatory proteins that act as site close to the promoter; sigma interacts with promoter
e: positive & negative control by regulatory proteins that act as sites close to AND far from promoter; mediator required
Term
bacteria VS eukaryotes: RNA processing
Definition
b: rare
e: extensive processing; alternative splicing of introns
Term
bacteria VS eukaryotes: mRNA stability
Definition
b: rarely used for control
e: commonly used; RNA interference limits the life span or translation rate of many mRNAs
Term
bacteria VS eukaryotes: translation
Definition
SAME FOR BOTH
Term
bacteria VS eukaryotes: post-translational modification
Definition
same except eukaryotes also have uibiquitination targets proteins for destruction by proteasome
Term
proto-oncogenes
Definition
genes that stimulate cell division
Term
oncogene
Definition
an allele that promotes cancer development
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