HMB265H1 Lecture Notes - Pax6, Cooperative Binding, Epigenetics

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Published on 1 Apr 2011
School
UTSG
Department
Human Biology
Course
HMB265H1
LECTURE 22
Final Exam:
April 12th from 2-4pm
Both sections
20-25% based on first semester
Rest based on second semester
Tutorial
Quiz epigenetics and genetics
oLook over calculations for odds ratios and lod ratios
oQuantitative genetics calculations
Regulated gene expression
All start with same types of cells, stem cells, containing same amount of genes,
DNA
Genes regulated by other factors and proteins within genome
Model organisms used to study development
oZebrafish
oNematode c elegans
oArabidopsis
oMouse
oFruit flies
oUsed to
Small size so easily manipulated
Look at flies and mice to drive development in humans
Pathways and genetic mechanisms conserved
What occurs in flies, occur in humans
Genomes sequenced so can find genes with mutant
phenotypes
All living forms are related
Fly
Loss of function of eyeless gene in drosophila = > no eye or small eye forming
Pax-6 gene is homolog of eyeless
Analog in humans called Aniridia
MUTATIONS
oNo functional copies of aniridia eyes embryos have no eye formation,
lethality in utero
Homozygous loss of function leads to embryonic lethality
oHeterozygote lack one or two irises
One wildtype only
Knockout reverse genetics
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To see what genes are important in what pathways? What defects result? Genes
important for what?
Forward geneticsmutagenize model organisms
oCross mutant mice with wildtype mice to perform phenotypic analysis
Drosophila so important
oBest genetic model organism THUS best model to study function of genes
in development
oEmbryo to adult = 10-11 days at 23 degrees C
oGenes positioning relationship btw axis conserved among species
Correct formation of axises in embryo lead to normal adult fly
1995 Nobel prize for discoveries concerning early development of drosophila
embryos
Found the genes controlling axis and that they were conserved
Different classes of drosohpila genes important for patterning of embryo
Anterior posterior pattern development focused today
oFirst class is maternal effect genes
Maternal effect mRNAs deposited in early embryo by mother
These genes direct formation of anterior, posterior axis in fly
Genotype of mother important
If mother has at least one wildtype copy of maternal effect
gene, then will have functional maternal affect protein
If lack protein, then embryo will lack functional maternal
affect protein, resulting in mutant embryo
Father does not matter true for many species, including
humans
Mothers genes that set up axis
oMust have at least one wildtype copy in order to have
normal maternal affect proteins
Present in concentration gradient
Bicoid = maternal effect gene, deposited and localized to
anterior portion of drosophila embryo
Gradient
oEmbryo synsinitia
Nuclear division without cytoplasmic division
One embryo has many nuclei, but not cellular
division
So easy for RNAs deposited to diffuse from
one end to other
If bicoid at anterior end, see gradient of
expression from antieror to posterior
Very little expression when get past embryo
Embryos lacking bicoid protein because
mother had no functional copies of gene
www.notesolution.com
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Document Summary

 quiz epigenetics and genetics: look over calculations for odds ratios and lod ratios, quantitative genetics calculations.  all start with same types of cells, stem cells, containing same amount of genes,  genes regulated by other factors and proteins within genome.  model organisms used to study development: zebrafish, nematode c elegans, arabidopsis, mouse, fruit flies, used to. Look at flies and mice to drive development in humans: pathways and genetic mechanisms conserved, what occurs in flies, occur in humans, genomes sequenced so can find genes with mutant phenotypes. Loss of function of eyeless gene in drosophila = > no eye or small eye forming.  mutations: no functional copies of aniridia eyes embryos have no eye formation, lethality in utero.  homozygous loss of function leads to embryonic lethality: heterozygote lack one or two irises. Forward genetics mutagenize model organisms: cross mu tant mice with wildtype mice to perform phenotypic analysis.