The Paradigm of Differential Gene Expression Flashcards
approximately how many protein encoding genes are present in humans?
25,000
at what 4 steps can regulation occur for the selective expression of gene products?
- differential gene transcription
- selective nuclear RNA processing
- selective mRNA translation
- differential protein modification
differential gene expression refers to
which genes are allowed to be transcribed within the nucleus
selective nuclear RNA processing refers to
which transcribed RNA sequences will make it to the cytoplasm
selective mRNA translation refers to
which mRNA is translated into proteins
differential protein modification refers to the determination of
which proteins are activated/functional
chromatin is a form of
DNA unique to eukaryotic cells
is chromatin found in prokaryotic cells?
NO
define nucleosome
basic unit of chromatin which contains the genetic information
the nucleosome structure is comprised of
histone subunits
the histone subunits of nucleosomes are encased with
2 bands of 147 DNA base pairs
histones are
octamer protein subunits
linker proteins contain _________ base pairs that link…
60-80
adjacent nucleosomes
what is the primary type of histone bound to the linker section?
histone H1
what prevents uncoiling of nucleosomes?
tightly joined nucleosomes linked together
the tight linkage between nucleosomes allows for
polymerase enzymes to bind & transcription proceeds
H1 represses or regulates the…
transcription of DNA to mRNA
what prevents the uncoiling of nucleosomes and DNA?
acetylation of histones
what represses or prevents the uncoiling of nucleosome units?
methylation
define exons
regions of the DNA which code for a protein
define introns
regions of DNA not expressed in the final amino acid sequence of a protein
promotor sites are the binding location for
RNA polymerase enzymes on DNA
promoter sites allow for transcription of
DNA to mRNA
initial nuclear RNA consists of
- promotor site
- cap sequence
- tail sequence
the cap sequence is found at what end of RNA?
5’
poly A tail is found at the
3’ end of RNA
enhancers are
DNA sequences which control the efficiency and rate of transcription from a promoter region
negative enhancer prevent the
premature formation of proteins and cells
negative enhancers can maintain the proper sequnce of
morphogenesis & organogenesis
transcription factors bind to the
enhancer/promoter regions to activate/repress transcription of a gene
transcription factors recruit
acetyl transferases
methyltransferases
acetyl transferases loosen the…
methyltransferases tighten the
histones and nucleosomes for transcription to occur
histone complex to repress transcription
transcription factors can form bridges to form a loop of DNA this causes
enhancer/promoter region to be closer together causing more efficient transcription
why are totipotent stems cells still capable of forming all cell types?
ICM has not undergone methylation
censorship refers to different cell types represented by the
processing of specific nuclear RNA transcripts into mRNA
differential splicing leads to an
assortment of various combinations of exons
due to differential splicing for humans one gene produces
multiple polypeptides or proteins
due to differential splicing for prokaryotes one gene produces
only ONE polypeptide or protein
what is the downside of having 1 gene producing many polypeptides?
a single gene mutation can lead to abnormalities of multiple proteins
what are spliceosomes?
a modified form of RNA which binds to nRNA strand to excise and ligate
spliceosomes are capable of
removing a mutated segment of RNA so transcription can proceed normally
what protects the mRNA from rapid enzymatic degradation in the cytoplasm?
the poly-A-tail
the maintenance and stabilization of the mRNA allows for more
efficient synthesis of its protein product
an mRNA strand w/o a tail or cap would be
degraded before translation at ribosomes can occur
the oocyte/egg stores some mRNAs that will be used ONLY
after fertilization
the mRNAs stored in the oocyte code for proteins that are needed for
- cleavage
- actin and cytoskeleton strands
- cyclin proteins
cyclin proteins are used to
regulate the timing of cell division
a polypeptide is a
non-function protein precursor
