How is it that all cells in an organism have the same DNA, yet they are so different in function?
Cellular Differentiation: process through which cells become specialized in structure and function
-regulation of gene expression cause cellular differentiation
What is ‘housekeeping’ gene expression like?
Housekeeping genes: required for basic cell maintenance so transcribes in all cells (ex. RNA pol)
What do homeotic genes control?
are master control genes:
groups of genes to determine body plan development
mutations in homeotic genes have large effects on body plans
genes are conserved (similar) in widely different species
What is an operon?
-A cluster of
genes with related functions
sequence that turns genes on or off
How is the lac operon externally regulated? (know RNA polymerase, the promoter sequence, operator sequence, and the repressor protein, and what they do)
Polymerase: makes RNA from DNA template by binding to the promoter sequence
Sequence: DNA segment upstream from the lac genes where RNA Pol binds to
initiate transcriptions. Does not code
Sequence: A DNA segment that sits between the promoter sequence and the genes
for lactose enzymes; can bind with repressor
molecule which can either bind to lactose or to the operator to physically
block the attachments of RNA pol to the promoter sequence
How is gene expression in a prokaryote different from expression in a eukaryote?
two copies of each gene
expression is turned off without help from a regulatory protein
regulatory sequence for each gene, although many share particular sequences or
proteins involved in their transcription
-do not typically have operons
-one copy of
nucleus, so translation occurs immediately as mRNA is produced (no splicing)
-genes are on
unless a regulatory protein is blocking gene expression
What is the mechanism of gene expression
in a eukaryote?
How do microRNAs regulate gene expression?
microRNAs bind with mRNA to block translation and to target the mRNA for destruction
What is RNAi?
RNA interference -biological process in which RNA molecules inhibit gene expression, typically by causing destruction to specific mRNA molecules
What is special about stem cells?
Are produced through therapeutic cloning and are not completely differentiated
Briefly explain the ways (shown below) in which protein presence is controlled in a cell: DNA packing Transcription factors and enhancers (regulation of expression- know about activators and repressors) mRNA processing and degradation microRNA Initiation of translation Protein activation and life span
tightly packed DNA physically prevents RNA pol from transcribing the DNA
factors: protein involved in regulating DNA transcription in eukaryotes
-activators: proteins which bind to ENHANCER SEQUENCE or the
promoter to encourage transcription
-repressors: proteins which bind to SILENCER SEQUENCE or the
promoter to discourage transcription
and decay: in many species one gene can make more than one protein
-alternative splicing: a
single mRNA transcript can produce more than one protein through different
-RNA decay: mRNA can last from
hours to months; protein production is possible while mRNA is present
small RNA molecules, bind with mRNA to block translation and target the mRNA
for destruction ) commonly used in human cells)
translation: proteins can bind to mRNA on the 5’ end to block translation
activation and breakdown: enzymes often must cut a polypeptide chain to make it
a functional protein
-proteins may last hours to
How does a signal transduction pathway communicate information about the environment to the nucleus of a cell?
a signal transduction pathway
-a molecule outside the cell
binds with a receptor protein
-other molecules carry the
information inside the cell
-eventually, a transcription
factor is activated
-the transcription factor
binds to DNA & regulates appropriate genes
What does a microarray measure?
Measures mRNA expressed in a particular circumstance or condition
What is a microarray ‘probe’?
each DNA spot contains picomoles of a specific DNA sequence
What is a microarray ‘target’?
What are: DNA, mRNA, cDNA?
DNA: Deoxyribonucleic acid is a molecule that encodes the genetic instructions mRNA: messenger RNA- carries information from DNA in the nucleus to cytosol in order to make protein cDNA:
Why is reproductive cloning difficult in a laboratory?
What is special about stem cells?
Place embryonic stem cell, adult stem cells, and adult skin cells in order from least differentiated to most differentiated.
cells: extracted before differentiation has taken place, so may potentially be
used to make new body tissues/organs and can divide indefinitely
cell: retrieved from cord at birth
cells: partially differentiated cells that replace a particular group of cells
in differentiated individuals
What is the difference between an
oncogene and a proto-oncogene?
genes that are currently causing cancer
normal genes with the potential to cause cancer if mutated (through cellular
mistakes or viral insertion)
Potential exam question: Contrast the ways that a cell might regulate genes whose proteins perform a life-saving function due to a rapidly appearing threat vs genes whose proteins are helpful but not critical and only occasionally required. Mention the disadvantage and the advantage of regulating each type of gene in this way