High School Biology-Chemistry SMILE Meeting
27 February 2001
Notes Prepared by Porter Johnson
Ben Stark (IIT Biology) Mendel's First Law
He asked about the inheritance pattern of the offspring with respect to red
and yellow corn. He described the following experiment that he had done
We conclude that R (red) is dominant over r (yellow). For every gene there are two
copies per cell, so you can have RR (red), Rr (red), and rr
- Take pollen from red and yellow corn, and place on corn silks of opposite type.
- Wait for the seeds to develop on cobs, and see the results. All are red.
- The first generation is then crossed, and their offspring examined at full
development. Some are red and some are yellow, but not in the same proportion.
- R gene (alleles) Þ color (R: red or r:
yellow) of kernel.
Gametes have only one gene, but body cells have two For gametes we have the
- RR Þ 100 % R
rr Þ 100 % r
Rr Þ 50 % R and 50 % r
We represent the possibilities through the Punnett Square for the first
cross: RR ´ rr:
|| Rr (red)
|| Rr (red)
Now the Punnett Square for the second cross: Rr ´ Rr:
|| RR (red)
|| rR (red)
Thus, we expect the second generation to by 75 % red and 25 %
yellow. Actual results with 150 seeds:
Pat Riley (Lincoln Park HS) Gas Laws
Part involving some mathematics:
- She placed a plunger of a syringe on a convenient and simple setting, say 10 or
to a particular volume. We predicted what would happen to the volume if
we held our thumb over the opening and pushed on the plunger. There was
general agreement that the volume would decrease.
Boyle's Law tells us that, as the volume of fixed amount of gas
decreases, the pressure increases---where pressure is defined as force per
Now we placed a hand on a piece of paper and traced its outline. When we
push on our hands, we are applying pressure only over the region traced on the
- Set a large syringe set at a volume of 100 cm3. Then
place the tip onto a rubber stopper to make a seal. We applied additional pressure by placing
books on the stopper, measured the resulting volumes, and made the following table:
(Number of Books)
||Inverse Volume (cm-3)
||10.0 ´ 10-3
||10.3 ´ 10-3
||10.8 ´ 10-3
||11.6 ´ 10-3
||13.3 ´ 10-3
||14.3 ´ 10-3
- Kinetic theory states that all gaseous matter is composed of particles
that move randomly in straight paths until they collide. They then
bounce off in a new direction, until the next collision. Collisions of
the particles with the walls of the container produce pressure. As you
reduce the volume, there are more collisions with the wall, and hence more
- As you increase the pressure on the syringe, the gas particles become
closer and closer together.
More mathematical part:
To estimate the absolute pressure of the air in the room, make a graph of
(Number of Books) versus the Inverse Volume (cm-3). The results will look like this
Pressure | *
# books | *
3 | *
| 2 4 6 8 10 12 14 ´ 10-3
| 1/V .
-3 | .
-6 | .
-9 | .
Atmospheric pressure [as measured in "number of books" on syringe] corresponds to the crossing
point on the vertical axis; the vertical intercept,
11 or 12 books.
Next presentation: Charles Law
Notes taken by Therese Donatello.