Download triploid

Journal 11/17/16
If you recall, humans have 2 of each chromosome - this
is how we get dominant and recessive and stuff. What
would be different if we naturally had 3 of each
chromosome? Or 4? Come up with a guess or an idea.
Objective
To learn about multiple
gene copies in different
species
Tonight’s Homework
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Research an aneuploidy disease
Euploidy
We know that humans have 2 of each
chromosome. Each chromosome provides a “T”
or a “t” allowing us to get combinations like “Tt”
for a person.
Most of the animals you see and interact with on
a daily basis have genes like this. We call
creatures like this diploid (2n).
But not all are. Some creatures have only 1 of
each chromosome. They’re haploid (n). Some
have 3 and are triploid (3n). And some even
have 4 and are tetraploid (4n).
Euploidy
Haploid organisms can only have “t” or “T”.
Triploid can have things like “tTt”, and tetraploid
can have things like “TttT”.
So… where do we see this and what does it do?
Most species that are diploid have haploid
reproductive cells. Example: a cell that’s just “t”
from a father combines with one that’s just “T”
from a mother, to make a child with “Tt”. We
have 2 haploid cells come together to make a
new diploid person.
Euploidy
Some diploid species have the option of
reproducing and creating haploid children all by
themselves, without a mate.
For example, when you eat chicken eggs, you’re
eating just what the female has produced. That
egg is haploid and just has an “X” chromosome.
The egg would need a male to fertilize it to
become “XX” or “XY” and actually develop into a
chicken.
But some creatures can tell that egg to go
ahead and turn into a living creature anyways –
just one that has only half the genes as normal.
This process is called parthogenesis.
Euploidy
Examples of animals that can do this:
Euploidy
Triploid organisms only exist in a few plant
species. The diagram below shows why. When a
triploid cell divides, we end up with cells that
have 2 of some chromosomes and 1 of others.
This unbalancing is bad because when 2 of
these cells come together,
we have no guarantee that
things will balance out again.
They could get worse!
So most triploid creatures
are sterile (can’t have kids).
We artificially create triploid
fruit because it’s bigger.
Euploidy
Tetraploid creatures aren’t super rare in the
plant kingdom. Like triploids, though, most
tetraploid cells have problems forming gametes.
The chromosomes don’t line up and split
properly, so most tetraploid plants reproduce by
parthogenesis.
To have tetraploid plants, we can either have 4
copies of every chromosome (4n), or we can
have 2 copies of 2 completely different sets of
chromosomes (2n1 + 2n2). This would be like
having a human who has full sets of 2 peoples’
DNA!
A lot of potatoes and corn are tetraploid.
Learning About Aneuploidy
Tomorrow we’re going to learn about aneuploidy –
genetic problems where a person ends up with a single
extra chromosome, or is missing a single chromosome.
Your job for homework is to look up one of the following:
Down Syndrome
Patau Syndrome
Turner’s Syndrome
Edwards Syndrome
Klinefelter Syndrome
Trisomy 8
Trisomy 9
For the disorder you pick, you need to find the following
information:
1) What chromosome is affected by this disorder?
2) What major problems does it cause?
3) How rare is it?
Homework Time
You have the rest of class to start in on your homework.
p 133:1-4
Exit Question
Something that has genes like “GgG” would be…
Haploid
Diploid
Triploid
Tetraploid
A freak
Nonexistent