BIOLOGY 1A03 - Theme 3 - Review Lecture - Module 3 & 4

what is the difference between gene regulation in prokaryotes and eukaryotes?

eukaryotic genes each contain their own transcriptional regulation factors, and are not grouped into operons based on overlapping and common functions

what are the four main trans-acting structures that bind to eukaryotic promoter regions?

basic helix-loop-helix, helix-turn-helix, zinc finger and leucine zipper

where do transcriptional factors bind onto on eukaryotic genes?

promoter regions

where do transcriptional activator proteins bind to on eukaryotic genes?

enhancer regions

what components make up the transcriptional complex for eukaryotic genes?

transcriptional activator protein, mediator complex, RNA polymerase and general transcription factors

in situ hybridization

evaluation of gene expression with an organism using small living samples from the organism

limitation of in situ hybridization

this method can only be utilized to observe gene expression of small and transparent organisms

What are the methods of measuring eukaryotic gene expression?

globin gene expression in development, isolation of mRNA and microarray analysis

when are gamma-globin genes expressed?

throughout infancy

when are beta-globin genes expressed?

throughout adulthood

what is the difference between beta- and gamma-globin molecules found in hemoglobin?

gamma-globin molecules can bind oxygen more strongly compared to beta-globin molecules

Petri dish and isolation of mRNA method of measuring gene expression

cell lysis and specialized separation are used to isolate genes of interest, in which reverse transcription is applied to produce fluorescent cDNA

microarray analysis

measurement of the activity of many genes by quantifying gene products

fluorescence analysis - mostly one fluorescence

that gene is more expressed in the designated cell type

fluorescence analysis - mixture of fluorescence - novel fluorescence produced

that gene is equally expressed in designated cell types

at what level is microarray analysis used to measure gene expression?

the transcriptional level

Limitations of microarray analysis

does not show gene expression at the translational, post-transcriptional or post-translational points`

what are the types of eukaryotic regulation of gene expression?

histone modifications, DNA methylation, mRNA stability and protein stability

histone modification

regulation of the amount of mRNA produced, chemical modification, does not alter DNA sequence

DNA methylation

regulation of the amount of mRNA produced, chemical modification, does not alter DNA sequence

mRNA stability

regulating the amount of mRNA translated

protein stability

regulation of the amount of time a protein can function within the cell

method of regulation - histone modification

positively charged tails of histone interact with negatively charged phosphates of DNA, acetylation of tails weakens their interaction with DNA may permit some transcriptional factors to bind to DNA

types of histone modification

acetylation and methylation

A histone modification occurs in which one acetyl group is added, what is the result on the overall ability of the DNA to be transcribed?

transcription would be favoured

A histone modification occurs in which five methyl groups are added, what is the result on the overall ability of the DNA to be transcribed?

transcription is prohibited, because the addition of this many methyl groups leads to starrick hindrance, which restricts transcriptional factors from binding to the promoter regions of DNA

what type of regulation does histone modification induce?

transcriptional regulation

what type of regulation does DNA methylation induce?

transcriptional regulation

what type of regulation does mRNA stability induce?

post-transcriptional regulation

what type of regulation does protein stability induce?

post-translational regulation

Describe the process of DNA methylation.

heavy methylation occurs to cytosine/CpG islands near a promoter region on DNA, which causes starrick hindrance, and therefore inhibits transcription.

Describe the process of mRNA stability as a post-transcriptional regulator of gene expression.

there are two RNA molecules that are produced that inhibit transcription, miRNA and siRNA. miRNA creates hairpin structures which are further processed into fragments which activate RNA-induced silencing complexes. siRNA are exact replicas of their target mRNAs in which they cleave and cut the target mRNA, causing degradation.

Describe the process of protein stability as a post-translational regulator of gene expression.

proteasomes break down unneeded or damaged proteins which have been tagged by a molecule known as ubiquitin. Through the process of polyubiquitinelation, a chain/tag of ubiquitin is added onto the protein and is recognized by the proteasome. The ubiquitin tag is removed upon arrival at the proteasome, and the protein is threaded through and degraded as they are cleaved.