Biology 1202B Lecture Notes - Lecture 19: Hayflick Limit, Stem Cell, Cell Potency

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20 Mar 2019
Department
Professor
Mon, Mar. 18/19 Lecture 19: Controlling Gene
Expression I
Control of Gene Expression I
How genes are regulated?
DNA and proteins both contribute to the importance of gene expression
Cell Differentiation
Process of becoming another cell
Totipotent cells can become a human being
o Stem cell
Blastocysts contains the cells of the inner mass cells which have the ability to differentiate
(pluripotent- they cannot become a human being but anything else - they are missing the outer
cells)
Their genome is the same, but individually they can differentiate to perform various functions
Genome consists of 20 000 genes
Adults maintain cells that have the ability to regenerate
o I.e heart cells, stem cells (not one that is approaching its Hayflick limit) 7
Control of gene suppression - what genes are expressed, at temporal and expression level
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2
Transcript: Non coding or coding, the RNA sequence post transcription
Product of transcription
Transcriptone - is looking at all of the transcripts as a whole
Controlling Gene Expression
Transcription initiation
Don’t start the transcription process if the gene is not needed to be expressed
Tissue specific transcription factors
Specific to each tissue only present in the kidney vs heart vs liver
Downstream and upstream regulators which bind to regulatory proteins
Transcription factors that bind to regulatory regions and promotors
Repressors bind to the regulatory regions an repress transcription
Differential and Temporal Gene Expression
DNA of all differentiated cells are identical (very similar but not exactly identical due to mutations
in somatic cells which accumulate over time)
Every cell nucleus contains complete genome in the fertilized egg
Genes that are not used have the capacity to be fully functional (they are always there)
Only a small percentage of the genome is expressed in each cell, transcripts are specific that cell
type
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