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Lecture 21

HMB265H1 Lecture Notes - Lecture 21: Body Plan, Forward Genetics, Embryonic Stem Cell

Human Biology
Course Code
Maria Papaconstantinou

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HMB265 Lecture 21:
Many advantages of the mode systems are because of their ease of growing, they can be grown in large
numbers, and theres lots of tools and resources available for these model organisms.
Why use:
The #1 reason we use them is because they are easy to grow. There are many developmental pathways
that have been conserved across the animal kingdom.
The homologous gene to the eyeless gene is pax-6, and fi you knock out this gene, it causes an eyeless
These people are missing their iris, causing the pupil to be deformed. People with this disease have
reductions in their sharpness of vision and their sensitivity to light. This is an autosomal dominance
mutation. In the homozygous form, this mutation is lethal resulting in severe brain damage.
Forward genetics is where we introduce a compound that will induce chemical mutagenesis in the
mouse, and we cross it with wildtype phenotypes and depending on the mutation, in the progeny there
will be different phenotypes.
Stem cells can even become embryonic stem cells. Embryonic stem cells are pluripotent, meaning they
can become any cell type. Adult stem cells are pultipotent, meaning they can only become some types
of cells. Embryonic stem cells can be induced to differentiate into many different types of tisues, and
they can be used for theraprutic purposes. We can regenerate cells missing in a specific disease using
this method. In order to generate embryonic stem cells, you have to destroy an early embryo which
raises ethical concerns. This is known as theraprutic cloninc. Reproductive cloning is taking a nucleus of
a cell from a donor and implanting the nucleus into a stem cell, and we implant the cell into a female
and it develops a clone of the donor.
They can be grown easily and their life cycle is days, and their development is easy to see because their
exoskeleton is on the outside, and this makes it very easy to study mutations in the body plan of
drosophila. It’s a odel orgais to see ho the od pla is set up, ad a gees that ere foud
were tested in humans to see if they have the same effect.
They diided the mutants into different classes, the the classes effect development in diff ways. The pink
are active genes. The gap genes like krupple and nurps where there is gaps. Pair rule genes act as they
are expressed in every other segment, and mutants will miss part of each pair of segments. Segment
find more resources at
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