SCIE1106 Lecture Notes - Lecture 23: Histone Deacetylase, Gene Expression, Nissan L Engine
L24 Regulation of Gene Expression (Eukaryotes)
•
Process of differentiation
•
Complexity of chromosome structure
•
Role of chromosome in gene expression
•
Somatic,germline,nucleosome,chromatin
remoldeing, chromatin remodeling complex,
histone modification, histone
acetyltransferase,histone deacetylase
Changes in gene expression, must account for
1. Developmental changes
2. Differentiation
Hypo A- Loss/gain of genes accounts for changes
Hypo B- If genes are neither lost/gained → changes in
their expression must account for changes in
development/differentiation
• DNA from undifferentiated/differentiated cells
retain capacity to produce a normal individual: no
losses occur during differentiation.
• Somatic nucleus results in same development as
normal egg nucleus → no genes lost/added
during development from egg to tadpole → hypo
B is correct
Differentiation, as a consequence of changes in gene
expression
• During development, cells commit to specific
fates & differentially express subsets of genes.
• Daughter cells may differ with respect to
regulatory instructions & development fate, so
new cells become differnet to their parent cell
Undifferentiated/ Differentiated cells produce different,
specific, mRNAs/proteins
• A single cell (eg egg) may give rise to a complex,
multicellular organism(human), composed of 3
trillion cells and 200 different cell types
o Organised into tissues, organs
o That perform different, specialized
functions
• Different cell types make different sets of
proteins, specialized tissues/cells which
o Can be recognized morphologically
• Early embryo → is characterized by rapid cell
division, followed by differentiation
o The genes expressed allow the embryo to
fulfil functions associates, with division,
and differentiation that is appropriate to
its developmental state
e.g
A, D – switched on in differentiated cells
B – switched off
C- constitutively expressed gene
Microarray analysis of gene expression
• Revealed massive changes during development of
human embros
• Shows that large # of genes are up/down
regulated, depending on the developmental stage
o By studying thousands of different
mRNAs simultaneously
o Is used to probe mRNA populations from
developmental stages
Genes that are expressed in every/all cells
• Those kind of genes are aka house-keeping genes/
constitutive genes
o House-keeping → required for the
maintenance of basic cellular fx
o Constitutive→ expressed in all cells of an
organism
• House keeping genes
o May be expressed at a constant rate/
varying expression levels
o Facultative genes → expressed when
required
o Inducible genes → expression is
responsive to changing
environments/conditions, or may depend
on the position in the cell cycle
• All of these require gene promoters +
transcription factors but the regulatory elements
in the promoters/ transcription factors required
depend on the gene + gene’s regulation
Genotypes → Phenotypes
• Cells change/differentiate to carry out specialized
tasks
• Marked by a change in cell morphology
(less/more mt, cp) and is usually preceded by
rapid proliferation( in amount)
• Differential gene expression from the same
nuclear repertoire, is accomplished by the
regulation of gene expression at several levels
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Document Summary
Changes in gene expression, must account for: developmental changes, differentiation. Hypo a- loss/gain of genes accounts for changes. Hypo b- if genes are neither lost/gained changes in their expression must account for changes in development/differentiation: dna from undifferentiated/differentiated cells retain capacity to produce a normal individual: no losses occur during differentiation. Somatic nucleus results in same development as normal egg nucleus no genes lost/added during development from egg to tadpole hypo. A, d switched on in differentiated cells. Microarray analysis of gene expression: revealed massive changes during development of human embros. Shows that large # of genes are up/down regulated, depending on the developmental stage: by studying thousands of different mrnas simultaneously. Is used to probe mrna populations from developmental stages. Solitary genes + gene families: 25-50% of eukaryotic genes are solitary, occur as 1 copy, might have specialized. 3rd thoracic segment: wings develop from the 2nd thoracic segment bothorax mutants have 4 wings instead of 2 now.
