Student presentation on meiosis Feb' 3rd'

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Student presentation on meiosis Feb. 3rd.

• Need 3-4 students to sign up today for this
  presentation before your leave.

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HomeworkWhat type of inheritance other than
Dominant can this be?
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HomeworkWhat type of inheritance other than
Dominant can this be?
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Further molecular definitions of the gene and how
gene expression leads to phenotypes.
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The central dogma
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Genotype
transcription
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AAAA
translation
phenotype
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Genotype
Mutations In the DNA
Transcription (efficiency?)
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AAAA (stability, localization,etc.?)
Translation (efficiency, etc.?)
(stability,protein folding, local structure,
interactions, etc.?)
phenotype
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Genotype does not always equal phenotype.

• Examples
• Silencing
• Imprinting
• Somatic mutations/Loss Of Heterozygousity (LOH)
• Genetic background effects
• Environment/Conditional mutants

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Yeast as a model system.

• 1.Easy/cheap to grow in the lab.
• 2.Can grow as a haploid cell.
• 3.Excellent for genetics can induce meiosis in
  the lab.
• 4.Genetics allows for screening the whole genome
  for gene function.

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The yeast cell cycle as model for genetic
dissection of gene function and cell cycle
regulation.
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Cells not committed, Stationary phase.
START Nutrient sensor
Cells committed to cell division
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Cells not committed, Stationary phase.
START Nutrient sensor
Cells committed To cell division
In plant and animal cells START Is less well
defined. However, START can be thought of as a
decision point where cells environmental and
developmental signals that instruct the cell to
proliferate or not to proliferate.
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Cells not committed, Stationary phase.
START Nutrient sensor
Cells committed To cell division
In plant and animal cells the commitment
point is not as absolute as it is in yeast. For
example, different tissue types may arrest
(temporarily or permanently) at different points
during the cycle as a normal part of development.
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Cells not committed, Stationary phase.
START Nutrient sensor
Cells committed To cell division
Haploid cells sensitive to mating factor (a- or
a-factor) and block progression only if they have
not passed through START.
Hydroxy urea (HU) inhibits DNA replication and
thus cells in S-phase are sensitive to this drug.
HU treated cells will accumulate in S-phase in
a reversible manner.
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START Nutrient sensor
Bud emergence is a morphological landmark
(phenotype) that indicates where in the division
cycle a cell happens to be.
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START Nutrient sensor
Bud emergence is a morphological landmark
(phenotype) that indicates where in the division
cycle a cell happens to be.
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START Nutrient sensor
Medial nuclear division defines Progression into
mitosis.
Nuclear migration to the bud neck Defines entry
into mitosis.
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Cytokinesis (CK) and cell separation (CS) Define
the completion of of the cell division cycle.
START Nutrient sensor
Initiation of nuclear division Defines the
completion of mitosis.
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The goal of a regulated cell division cycle is
to Ensure that the genetic material is duplicate
Properly and that each for the two daughter
cells Inherit an equal share of the genetic
material.
Although the details of the yeast cell cycle
may differ from plant and animal cell cycles,
the molecules that drive the cell cycle engine
and make cells divide are almost all conserved
from yeast to humans to plants.
Furthermore, the essential order of the steps in
the cycle are conserved (with a few
special exceptions).
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How do we use phenotypes and genetics to dissect
the order of gene function in the yeast cell
cycle?
Mutations In the DNA
Transcription (efficiency?)
mRNA (stability, localization,etc.?)
Translation (efficiency, etc.?)
(stability,protein folding, local structure,
interactions, etc.?)
phenotype
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How do we use phenotypes and genetics to dissect
the order of gene function in the yeast cell
cycle? Remember that yeast cells are haploid!
Mutations In the DNA
Transcription (efficiency?)
mRNA (stability, localization,etc.?)
Translation (efficiency, etc.?)
(stability,protein folding, local structure,
interactions, etc.?)
phenotype
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How do we study yeast cell division mutants if
they are defective in cell division and thus do
not grow and divide?
Mutations In the DNA
Transcription (efficiency?)
mRNA (stability, localization,etc.?)
Translation (efficiency, etc.?)
(stability,protein folding, local structure,
interactions, etc.?)
phenotype
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Conditional Mutants!!
Mutations In the DNA
Transcription (efficiency?)
mRNA (stability, localization,etc.?)
Translation (efficiency, etc.?)
(stability,protein folding, local structure,
interactions, etc.?)
phenotype
30oC
37oC
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How do we assign function to genes based on
phenotypes?
Mutations In the DNA
Transcription (efficiency?)
mRNA (stability, localization,etc.?)
Translation (efficiency, etc.?)
(stability,protein folding, local structure,
interactions, etc.?)
phenotype
30oC
37oC
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What are terminal phenotypes and what is
their significance in assigning gene function?
Mutations In the DNA
Transcription (efficiency?)
mRNA (stability, localization,etc.?)
Translation (efficiency, etc.?)
(stability,protein folding, local structure,
interactions, etc.?)
phenotype
30oC
37oC
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Reciprocal shift experiments to determine the
execution point of a gene product.
START Nutrient sensor
Haploid cells sensitive to mating factor (a- or
a-factor) and block in a Reversible
manner progression only if they have not passed
through START.
Shift to restrictive Temperature Change mating
factor for HU
Hydroxy urea (HU) inhibits DNA replication and
thus cells in S-phase are sensitive to this drug.
HU treated cells will accumulate in S-phase in
a reversible manner.
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Next time Jan 27, 2005.

• Student presentation on the Hartwell CDC screen
  paper.
• Come prepared with questions!!